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WCF interview Questions

2010-09-09T02:44:00.000-07:00

How do I serialize entities using WCF?
LINQ to SQL supports serialization as XML via WCF by generating WCF serialization attributes and special serialization specific logic during code-generation. You can turn on this feature in the designer by setting serialization mode to ‘Unidirectional’. Note this is not a general solution for serialization as unidirectional mode may be insufficient for many use cases.

What are different isolation levels provided in WCF?
The different isolation levels:

1. READ UNCOMMITTED: – An uncommitted transaction can be read. This transaction can be rolled back later.

2. READ COMMITTED :- Will not read data of a transaction that has not been committed yet

3. REPEATABLE READ: – Locks placed on all data and another transaction cannot read.

4. SERIALIZABLE:- Does not allow other transactions to insert or update data until the transaction is complete.

What is a Binding ?

2010-09-08T06:01:00.000-07:00

What is Binding in Windows Communication Foundation ?
Windows Communication Foundation is a framework for building services that process XML messages. Windows Communication Foundation allows you to transmit messages using different transport protocols (such as HTTP, TCP, and MSMQ) and using different XML representations (such as text, binary, or MTOM, which is commonly referred to as the message encoding in Windows Communication Foundation). In addition, you can enhance specific messaging interactions with a suite of SOAP protocols, such as the various WS-* specifications around security, reliable messaging, and transactions. All three of these communication concepts—the transport, the message encoding, and the suite of protocols—are central to what happens on the wire at run time.

Interview Question and Answers WCF-10

2010-06-08T04:40:00.000-07:00

Will Windows Communication Foundation applications interoperate with Web services built with other technologi
es?
Yes. By default,services built with WCF will communicate with other services based on the interoperable Web services specifications. This means that WCF services will communicate with any application built on an infrastructure that also conforms to these standards. Microsoft is deeply committed to p
latform interoperability and is an active member of key standards organizations defining the latest Web services standards.

How to set the timeout property for the WCF Service client call?
The timeout property can be set for the WCF Service client call using binding tag. If no timeout has been specified, the default is considered as 1 minute.

What are the core components of an Windows Communication Foundation service?
A host environment—an application domain and process—in which the service runs;
A service class, implemented in C# or VB.NET or another CLR-based language that implements one or more methods;
One or more endpoints that allow clients to access the service.

What are different elements of WCF Srevices Client configuration file?
WCF Services client configuration file contains endpoint, address, binding and contract.

Interview Question and Answers WCF-9

2010-06-08T04:38:00.000-07:00

How does Windows Communication Foundation address Service Oriented Architecture (SOA)?
WCF is the first programming model built from the ground up to provide implicit service-oriented application development, enabling developers to work autonomously and build applications that are more version independent, thereby increasing application resilience to change.

How to deal with operation overloading while exposing the WCF services?
By default overload operations are not supported in WSDL based
operation. However by using Name property of OperationContract attribute, we can deal with operation overloading scenario.

[ServiceContract]
interface Isum
{
[OperationContract(Name = "MultiplyInt")]
int Multiply(int arg1,int arg2);

[OperationContract(Name = "MultiplyDouble")]
double Multiply(double arg1,double arg2);
}

Notice that both method name in the above interface is same (Add), however the Name property of the OperationContract is different. In this case client proxy will have two methods with different name MultiplyInt and MultiplyDouble.

Is Windows Communication Foundation going to interoperate with my existing applications?
The current plan is for Windows Communication Foundation to provide wire-level interoperability with WSE3, System.Messaging, .NET Enterprise Services, and ASMX applications. With minimal or no changes to code, applications built with these technologies will be able to call Windows Communication Foundation services and be callable by Windows Communication Foundation services.

How to configure Reliability while communicating with WCF Services?
Reliability can be configured in the client config file by adding reliableSession under binding tag.

Reliability is supported by following bindings only:
NetTcpBinding
WSHttpBindingWSFederationHttpBinding
WSDualHttpBinding

Interview Question and Answers WCF-8

2010-06-08T04:36:00.000-07:00

What is service and client in perspective of data communication?
A service is a unit of functionality exposed to the world. The client of a service is merely the party consuming the service.

1. A user has a service with a one-way operation that includes a fault contract, and he
gets an exception when he tries to host the service. Why?
This happens because, to return faults, the service needs some form of a two-way communication channel in place, which is not the case with one-way operations.

2. A user has a service he wants to expose on the Internet, and it needs to send notifications
out to its consumers. Would the WCF Duplex MEP be a good choice for
implementing this?
No. The WCF Duplex MEP can be problematic to enable, even inside an enterprise.
Its implementation depends upon the service establishing a connection back to the consumer, which can’t happen in certain scenarios, such as when the client’s machine uses NAT behind a firewall. On the Internet, where you are never certain
where your consumers are coming from, this type of callback channel would rarely, if ever, work. When you factor in the security risks it could pose and the scalability concerns with the fact that callback channels require the presence of sessions
between client and service, it isn’t a feasible solution.

3. You have a Data contract specifying a Person class from which you derive a Customer class. Does a Customer object automatically have a Data contract as well?
No. The Data contract is not inherited, so any derived class, such as the Customer class, would have to be explicitly declared as having a Data contract as well.

4. Your company has its own proprietary authentication mechanism, and you are required to authenticate every message coming into the service. What is the best way to handle using this mechanism with WCF?
Likely the best way to handle this would be to design a Message contract that accepts these proprietary authentication tokens in the header.

5. Can you support the Rpc SOAP style by using the DataContractSerializer?
Yes. You need only adorn your service with the DataContractFormatAttribute and explicitly set the attribute’s Style property to OperationFormatStyle.Rpc.

6. What does the “ABCs of endpoints” refer to?
The ABCs of endpoints refers to the three required elements that comprise a service endpoint: address, binding, and contract.

7. Which standard binding could be used for a service that was designed to replace an existing ASMX Web service?
The basicHttpBinding standard binding was designed to expose a service as if it were an ASMX Web service. This enables you to support existing clients as applications are upgraded to WCF.

8. What is the main disadvantage of using IIS to host a service?
Using IIS to host your services means that you will not be able to support non-HTTP protocols such as TCP, named pipes, and MSMQ. You will have access to the many built-in features available with IIS such as process recycling and messagebased
activation.

9. Which file specifies the types that your service will expose in IIS?
Service types are exposed through IIS by using the service file. This file must have an .svc file extension and should reside in the application directory for your IIS hosting application. This file will include an @ServiceHost directive, which specifies
the service name and language for the service code files. These files should be located in an App_Code subdirectory.

Interview Question and Answers WCF-7

2010-06-08T04:34:00.000-07:00

Where we can host WCF services?
Every WCF services must be hosted somewhere. There are three ways of hosting WCF services.
They are
1. IIS
2. Self Hosting
3. WAS (Windows Activation Service)
For more details see http://msdn.microsoft.com/en-us/library/bb332338.aspx

What is address in WCF and how many types of transport schemas are there in WCF?
Address is a way of letting client know that where a service is located. In WCF, every service is associated with a unique address. This contains the location of the service and transport schemas.

WCF supports following transport schemas
HTTP
TCP
Peer network
IPC (Inter-Process Communication over named pipes)
MSMQ

The sample address for above transport schema may look like
http://localhost:81
http://localhost:81/MyService
net.tcp://localhost:82/MyService
net.pipe://localhost/MyPipeService
net.msmq://localhost/private/MyMsMqService
net.msmq://localhost/MyMsMqService

Interview Question and Answers WCF-6

2010-06-08T04:32:00.000-07:00

What is binding and how many types of bindings are there in WCF?
A binding defines how an endpoint communicates to the world. A binding defines the transport (such as HTTP or TCP) and the encoding being used (such as text or binary). A binding can contain binding elements that specify details like the security mechanisms used to secure messages, or the message pattern used by an endpoint.

WCF supports nine types of bindings.

Basic binding
Offered by the BasicHttpBinding class, this is designed to expose a WCF service as a legacy ASMX web service, so that old clients can work with new services. When used by the client, this binding enables new WCF clients to work with old ASMX services.

TCP binding
Offered by the NetTcpBinding class, this uses TCP for cross-machine communication on the intranet. It supports a variety of features, including reliability, transactions, and security, and is optimized for WCF-to-WCF communication. As a result, it requires both the client and the service to use WCF.

Peer network binding
Offered by the NetPeerTcpBinding class, this uses peer networking as a transport. The peer network-enabled client and services all subscribe to the same grid and broadcast messages to it.

IPC binding
Offered by the NetNamedPipeBinding class, this uses named pipes as a transport for same-machine communication. It is the most secure binding since it cannot accept calls from outside the machine and it supports a variety of features similar to the TCP binding.

Web Service (WS) binding
Offered by the WSHttpBinding class, this uses HTTP or HTTPS for transport, and is designed to offer a variety of features such as reliability, transactions, and security over the Internet.

Federated WS binding
Offered by the WSFederationHttpBinding class, this is a specialization of the WS binding, offering support for federated security.

Duplex WS binding
Offered by the WSDualHttpBinding class, this is similar to the WS binding except it also supports bidirectional communication from the service to the client.

MSMQ binding
Offered by the NetMsmqBinding class, this uses MSMQ for transport and is designed to offer support for disconnected queued calls.

MSMQ integration binding
Offered by the MsmqIntegrationBinding class, this converts WCF messages to and from MSMQ messages, and is designed to interoperate with legacy MSMQ clients.
For WCF binding comparison, see http://www.pluralsight.com/community/blogs/aaron/archive/2007/03/22/46560.aspx

Interview Question and Answers WCF-5

2010-06-08T04:19:00.000-07:00

What are contracts in WCF?
In WCF, all services expose contracts. The contract is a platform-neutral and standard way of describing what the service does.
WCF defines four types of contracts.

Service contracts

Describe which operations the client can perform on the service.
There are two types of Service Contracts.
ServiceContract - This attribute is used to define the Interface.
OperationContract - This attribute is used to define the method inside Interface.
[ServiceContract]
interface IMyContract
{
[OperationContract]
string MyMethod( );
}
class MyService : IMyContract
{
public string MyMethod( )
{
return "Hello World";
}
}
Data contracts

Define which data types are passed to and from the service. WCF defines implicit contracts for built-in types such as int and string, but we can easily define explicit opt-in data contracts for custom types.

There are two types of Data Contracts.
DataContract - attribute used to define the class
DataMember - attribute used to define the properties.
[DataContract]

class Contact
{
[DataMember]
public string FirstName;
[DataMember]

public string LastName;
}
If DataMember attributes are not specified for a properties in the class, that property can't be passed to-from web service.
Fault contracts
Define which errors are raised by the service, and how the service handles and propagates errors to its clients.

Message contracts
Allow the service to interact directly with messages. Message contracts can be typed or untyped, and are useful in interoperability cases and when there is an existing message format we have to comply with.

Policy and Binding
Specifies the transport media such as HTTP or TCP. It aslo includes some of the securoty requirements. which are necessary for Commucation.
What is the address formats of the WCF transport schemas?
Address format of WCF transport schema always follow
[transport]://[machine or domain][:optional port] format.
for example:
HTTP Address Format
http://localhost:8888
the way to read the above url is

"Using HTTP, go to the machine called localhost, where on port 8888 someone is waiting"
When the port number is not specified, the default port is 80.

TCP Address Format
net.tcp://localhost:8888/MyService

When a port number is not specified, the default port is 808:
net.tcp://localhost/MyService

NOTE: Two HTTP and TCP addresses from the same host can share a port, even on the same machine.

IPC Address Format
net.pipe://localhost/MyPipe

We can only open a named pipe once per machine, and therefore it is not possible for two named pipe addresses to share a pipe name on the same machine.

MSMQ Address Format
net.msmq://localhost/private/MyService
net.msmq://localhost/MyService

Interview Question and Answers WCF-4

2010-06-08T04:17:00.000-07:00

What are different elements of WCF Srevices Client configuration file?
WCF Services client configuration file contains endpoint, address, binding and contract. A sample client config file looks like
<system.serviceModel>
<client>
<endpoint name = "MyEndpoint"
address = "http://localhost:8000/MyService/"
binding = "wsHttpBinding"
contract = "IMyContract"
/>
</client>
</system.serviceModel>

What is Proxy and how to generate proxy for WCF Services?
The proxy is a CLR class that exposes a single CLR interface representing the service contract. The proxy provides the same operations as service's contract, but also has additional methods for managing the proxy life cycle and the connection to the service. The proxy completely encapsulates every aspect of the service: its location, its implementation technology and runtime platform, and the communication transport.

The proxy can be generated using Visual Studio by right clicking Reference and clicking on Add Service Reference. This brings up the Add Service Reference dialog box, where you need to supply the base address of the service (or a base address and a MEX URI) and the namespace to contain the proxy.

Proxy can also be generated by using SvcUtil.exe command-line utility. We need to provide SvcUtil with the HTTP-GET address or the metadata exchange endpoint address and, optionally, with a proxy filename. The default proxy filename is output.cs but you can also use the /out switch to indicate a different name.

SvcUtil http://localhost/MyService/MyService.svc /out:Proxy.cs

When we are hosting in IIS and selecting a port other than port 80 (such as port 88), we must provide that port number as part of the base address:

SvcUtil http://localhost:88/MyService/MyService.svc /out:Proxy.cs

Interview Question and Answers WCF-2

2010-06-08T04:11:00.000-07:00

How to deal with operation overloading while exposing the WCF services?
By default overload operations (methods) are not supported in WSDL based operation. However by using Name property of OperationContract attribute, we can deal with operation overloading scenario.
[ServiceContract]
interface ICalculator
{
[OperationContract(Name = "AddInt")]
int Add(int arg1,int arg2);
[OperationContract(Name = "AddDouble")]
double Add(double arg1,double arg2);
}
Notice that both method name in the above interface is same (Add), however the Name property of the OperationContract is different. In this case client proxy will have two methods with different name AddInt and AddDouble.

How to configure Reliability while communicating with WCF Services?

Reliability can be configured in the client config file by adding reliableSession under binding tag.
<system.serviceModel>
<services>
<service name = "MyService">
<endpoint
address = "net.tcp://localhost:8888/MyService"
binding = "netTcpBinding"
bindingConfiguration = "ReliableCommunication"
contract = "IMyContract"
/>
</service>
</services>
<bindings>
<netTcpBinding>
<binding name = "ReliableCommunication">
<reliableSession enabled = "true"/>
</binding>
</netTcpBinding>
</bindings>
</system.serviceModel>
Reliability is supported by following bindings only

NetTcpBinding
WSHttpBinding
WSFederationHttpBinding
WSDualHttpBinding

What is Transport and Message Reliability?Transport reliability (such as the one offered by TCP) offers point-to-point guaranteed delivery at the network packet level, as well as guarantees the order of the packets. Transport reliability is not resilient to dropping network connections and a variety of other communication problems.

Message reliability deals with reliability at the message level independent of how many packets are required to deliver the message. Message reliability provides for end-to-end guaranteed delivery and order of messages, regardless of how many intermediaries are involved, and how many network hops are required to deliver the message from the client to the service.

Interview Question and Answers WCF-3

2010-06-08T04:07:00.000-07:00

What is the difference WCF and Web services?
Web services can only be invoked by HTTP (traditional webservice with .asmx). While WCF Service or a WCF component can be invoked by any protocol (like http, tcp etc.) and any transport type.

Second web services are not flexible. However, WCF Services are flexible. If you make a new version of the service then you need to just expose a new end. Therefore, services are agile and which is a very practical approach looking at the current business trends.

We develop WCF as contracts, interface, operations, and data contracts. As the developer we are more focused on the business logic services and need not worry about channel stack. WCF is a unified programming API for any kind of services so we create the service and use configuration information to set up the communication mechanism like HTTP/TCP/MSMQ etc
For more details, read http://msdn.microsoft.com/en-us/library/aa738737.aspx

What are various ways of hosting WCF Services?
There are three major ways of hosting a WCF services
• Self-hosting the service in his own application domain. This we have already covered in the first section. The service comes in to existence when you create the object of Service Host class and the service closes when you call the Close of the Service Host class.

• Host in application domain or process provided by IIS Server.
• Host in Application domain and process provided by WAS (Windows Activation Service) Server.
What was the code name for WCF?
The code name of WCF was Indigo .
WCF is a unification of .NET framework communication technologies which unites the following technologies:-
NET remoting
MSMQ
Web services
COM+

What are the main components of WCF?
The main components of WCF are
1. Service class
2. Hosting environment
3. End point

How to set the timeout property for the WCF Service client call?
The timeout property can be set for the WCF Service client call using binding tag.
<client>
<endpoint
binding = "wsHttpBinding"
bindingConfiguration = "LongTimeout"
/>
</client>
<bindings>
<wsHttpBinding>
<binding name = "LongTimeout" sendTimeout = "00:04:00"/>
</wsHttpBinding>
</bindings>
If no timeout has been specified, the default is considered as 1 minute.

interview question and answer wct-1

2010-06-08T04:04:00.000-07:00

What is three major points in WCF?
1) Address --- Specifies the location of the service which will be like http://Myserver/MyService.Clients will use this location to communicate with our service.
2) Contract --- Specifies the interface between client and the server. It’s a simple interface with some attribute.
3) Binding --- Specifies how the two paries will communicate in term of transport and encoding and protocols

What is WCF?
The Windows Presentation Foundation (WPF) is a next generation graphics platform that is part of .NET 3.0 and .NET 3.5. It allows you to build advanced user interfaces that incorporate documents, media, 2D and 3D graphics, animations, and web-like characteristics. In just 24 sessions of one hour or less, you will be able to begin effectively using WPF to solve real-world problems, developing rich user interfaces in less time than you thought possible. Using a straightforward, step-by-step approach, each lesson builds on a real-world foundation forged in both technology and business matters, allowing you to learn the essentials of WPF from the ground up

What is WCF?
Windows Communication Foundation (WCF) is an SDK for developing and deploying services on Windows. WCF provides a runtime environment for services, enabling you to expose CLR types as services, and to consume other services as CLR types.
WCF is part of .NET 3.0 and requires .NET 2.0, so it can only run on systems that support it.

Difference between WCF and Web services?
Web Services
1.It Can be accessed only over HTTP
2.It works in stateless environment
WCF
WCF is flexible because its services can be hosted in different types of applications. The following lists several common scenarios for hosting WCF services:
IIS
WAS
Self-hosting
Managed Windows Service

What are the various ways of hosting a WCF service?
Self hosting the service in his own application domain. This we have already covered in the first section. The service comes in to existence when you create the object of ServiceHost class and the service closes when you call the Close of the ServiceHost class.
Host in application domain or process provided by IIS Server.
Host in Application domain and process provided by WAS (Windows Activation Service) Server.

2009-06-16T06:33:00.000-07:00

This Junk of Code is used to display images on the GridView.

Here I'm creating a static DataTable with some data

The getUserData() Method will creates a DataTable with following fields PictureID,PictureURL, Title, DateAdded.


DataTable GetData()
    {
       
        DataTable dt = new DataTable();

        // define the table's schema
        dt.Columns.Add(new DataColumn("PictureID", typeof(int)));
        dt.Columns.Add(new DataColumn("PictureURL", typeof(string)));
        dt.Columns.Add(new DataColumn("Title", typeof(string)));
        dt.Columns.Add(new DataColumn("DateAdded", typeof(DateTime)));

        // Create the four records
        DataRow dr = dt.NewRow();
        dr["PictureID"] = 1;
        dr["PictureURL"] = ResolveUrl("~/DisplayingImages/Images/pic001.jpg");
        dr["Title"] = "Blue Hills";
        dr["DateAdded"] = new DateTime(2005, 1, 15);
        dt.Rows.Add(dr);

        dr = dt.NewRow();
        dr["PictureID"] = 2;
        dr["PictureURL"] = ResolveUrl("~/DisplayingImages/Images/pic002.jpg");
        dr["Title"] = "Sunset";
        dr["DateAdded"] = new DateTime(2005, 1, 21);
        dt.Rows.Add(dr);

        dr = dt.NewRow();
        dr["PictureID"] = 3;
        dr["PictureURL"] = ResolveUrl("~/DisplayingImages/Images/pic003.jpg");
        dr["Title"] = "Water Lilies";
        dr["DateAdded"] = new DateTime(2005, 2, 1);
        dt.Rows.Add(dr);

        dr = dt.NewRow();
        dr["PictureID"] = 4;
        dr["PictureURL"] = ResolveUrl("~/DisplayingImages/Images/pic004.jpg");
        dr["Title"] = "Winter";
        dr["DateAdded"] = new DateTime(2005, 2, 18);
        dt.Rows.Add(dr);

        return dt;
    }


< asp:GridView ID="GridView1" Runat="server" DataSource='< %# GetData() %>' AutoGenerateColumns="False" BorderWidth="1px" BackColor="White" CellPadding="3" BorderStyle="None" BorderColor="#CCCCCC" Font-Names="Arial">
            < FooterStyle ForeColor="#000066" BackColor="White">< /FooterStyle>
            < PagerStyle ForeColor="#000066" HorizontalAlign="Left" BackColor="White">< /PagerStyle>
            < HeaderStyle ForeColor="White" Font-Bold="True" BackColor="#006699">< /HeaderStyle>
            < Columns>
                < asp:BoundField HeaderText="Picutre ID" DataField="PictureID">
                    < ItemStyle HorizontalAlign="Center" VerticalAlign="Middle">< /ItemStyle>
                < /asp:BoundField>
                < asp:BoundField HeaderText="Title" DataField="Title">< /asp:BoundField>
                < asp:BoundField HeaderText="Date Added" DataField="DateAdded" DataFormatString="{0:d}">
                    < ItemStyle HorizontalAlign="Center">< /ItemStyle>
                < /asp:BoundField>
                < asp:ImageField DataImageUrlField="PictureURL">< /asp:ImageField>
            < /Columns>
            < SelectedRowStyle ForeColor="White" Font-Bold="True" BackColor="#669999">< /SelectedRowStyle>
            < RowStyle ForeColor="#000066">< /RowStyle>
        < /asp:GridView>

--
Enjoy the codeing

Sending email with embedded image using .net 3.5

2009-06-12T05:37:00.000-07:00

Now throw this junk of code we can able to send email with embedded Image. Its a method you can call this method in any event

We take host name from web.config you can find the code below

protected void btnSendEmail_Click(object sender, EventArgs e)
{
if (fileImage.HasFile)
{

//Holds message information.
System.Net.Mail.MailMessage mailMessage = new System.Net.Mail.MailMessage();
//Add basic information.
mailMessage.From = new System.Net.Mail.MailAddress(txtFrom.Text.Trim());
mailMessage.To.Add(txtTo.Text.Trim());

mailMessage.Subject = txtSubject.Text.Trim();
//Create two views, one text, one HTML.
System.Net.Mail.AlternateView plainTextView = System.Net.Mail.AlternateView.CreateAlternateViewFromString(txtBody.Text.Trim(), null, "text/plain");
System.Net.Mail.AlternateView htmlView = System.Net.Mail.AlternateView.CreateAlternateViewFromString(txtBody.Text.Trim() + "< image src=cid:HDIImage>", null, "text/html");
//Add image to HTML version
System.Net.Mail.LinkedResource imageResource = new System.Net.Mail.LinkedResource(fileImage.PostedFile.FileName);
imageResource.ContentId = "HDIImage";
htmlView.LinkedResources.Add(imageResource);
//Add two views to message.
mailMessage.AlternateViews.Add(plainTextView);
mailMessage.AlternateViews.Add(htmlView);
//Send message
System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
smtpClient.Send(mailMessage);

}

< Configuring with web.congif file
< system.net>
< mailSettings>
< smtp>
< network
< host="YOUR HOST HERE" />
< /smtp>
< /mailSettings>
< /system.net>

Sending Email Asynchronously .net 3.5

2009-06-12T05:09:00.000-07:00

Now throw this junk of code we can able to send email Asynchronously Its a method you can call this method in any event

We take host name from web.config you can find the code below

private void SendMail()
{

//Create message object and populate with the data from form
System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();
message.From = new System.Net.Mail.MailAddress(txtFrom.Text.Trim());
message.To.Add(txtTo.Text.Trim());
message.Subject = txtSubject.Text.Trim();
message.Body = txtBody.Text.Trim();

//Setup SmtpClient to send email. Uses web.config settings.
System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();

//Error handling for sending message
try
{
smtpClient.Send(message);
//Exception contains information on each failed receipient
}
catch (System.Net.Mail.SmtpFailedRecipientsException recExc)
{
for (int recipient = 0; recipient < recExc.InnerExceptions.Length - 1; recipient++)
{
System.Net.Mail.SmtpStatusCode statusCode;

statusCode = recExc.InnerExceptions[recipient].StatusCode;

if ((statusCode == System.Net.Mail.SmtpStatusCode.MailboxBusy) || (statusCode == System.Net.Mail.SmtpStatusCode.MailboxUnavailable))
{

System.Threading.Thread.Sleep(5000);
smtpClient.Send(message);
}
else
{
ErrorLabel.Text = recExc.Message;

}

}
}
//General SMTP execptions
catch (System.Net.Mail.SmtpException smtpExc)
{

ErrorLabel.Text = smtpExc.StatusCode.ToString();
}
catch (Exception ex)
{
//Log error to event log.
}
}

Configuring web.config file

< system.net>
< mailSettings>
< smtp>
< network host="YOUR HOST INFO HERE"/>
< /smtp>
< /mailSettings>
< /system.net>

Encrypting and Decripting values using Security Key

2009-06-11T23:28:00.000-07:00

This junk of code is used to Encrypt and Decrypt the values depending on a key called Security Key. Which is saved in the web.config file or in database.

public sealed class EncryptCard
{
private EncryptCard()
{
}

public static string Encrypt(string toEncrypt, bool useHashing)
{
if (!string.IsNullOrEmpty(toEncrypt))
{
byte[] keyArray;
byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

AppSettingsReader settingsReader = new AppSettingsReader();

string key = (string)settingsReader.GetValue("SecurityKey", typeof(String));
if (useHashing)
{
MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));

hashmd5.Clear();
}
else
keyArray = UTF8Encoding.UTF8.GetBytes(key);

TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();

tdes.Key = keyArray;
tdes.Mode = CipherMode.ECB;

tdes.Padding = PaddingMode.PKCS7;

ICryptoTransform cTransform = tdes.CreateEncryptor();

byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

tdes.Clear();

return Convert.ToBase64String(resultArray, 0, resultArray.Length);
}
else
{
return toEncrypt = null;
}
}

Decrypting above Encrypted value.
public static string Decrypt(string decryptValue, bool useHashing)
{
if (!string.IsNullOrEmpty(decryptValue))
{
byte[] keyArray;

byte[] toEncryptArray = Convert.FromBase64String(decryptValue);

System.Configuration.AppSettingsReader settingsReader = new AppSettingsReader();

string key = (string)settingsReader.GetValue("SecurityKey", typeof(String));

if (useHashing)
{

MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));

hashmd5.Clear();
}
else
{

keyArray = UTF8Encoding.UTF8.GetBytes(key);
}

TripleDESCryptoServiceProvider tdesProvider = new TripleDESCryptoServiceProvider();

tdesProvider.Key = keyArray;

tdesProvider.Mode = CipherMode.ECB;

tdesProvider.Padding = PaddingMode.PKCS7;

ICryptoTransform cTransform = tdesProvider.CreateDecryptor();
byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

tdesProvider.Clear();

return UTF8Encoding.UTF8.GetString(resultArray);
}
else
{
return decryptValue = null;
}
}
}

Here. I added the securityKey in web.config file
appSettings>

<add key ="SecurityKey" value="DOTNETMATRIX"/>
</appSettings>

Calling javascript in GridView RowCreated Event

2009-06-09T05:59:00.000-07:00

//This junk of code is used to call javascript in GridView RowCreated Event

protected void grdIssue_RowCreated(object sender, GridViewRowEventArgs e)
{
CheckBox chkHead = new CheckBox();
if (e.Row.RowType.ToString().Trim() == "Header")
{
chkHead = (CheckBox)e.Row.FindControl("chkbxHeader");
chkHead.Attributes.Add("onClick", "chkBocHeader(" + chkHead.ClientID + ",'H')");
}
else if (e.Row.RowType.ToString().Trim() == "DataRow")
{
CheckBox chkRow = new CheckBox();
chkRow = (CheckBox)e.Row.FindControl("chkboxRow");
chkRow.Attributes.Add("onClick", "chkBocHeader(this,'R')");
}
}

URL Encoding Reference

2009-06-09T05:34:00.000-07:00

URL Encoding Reference

ASCII Character	URL-encoding
space	%20
!	%21
"	%22
#	%23
$	%24
%	%25
&	%26
'	%27
(	%28
)	%29
*	%2A
+	%2B
,	%2C
-	%2D
.	%2E
/	%2F
0	%30
1	%31
2	%32
3	%33
4	%34
5	%35
6	%36
7	%37
8	%38
9	%39
:	%3A
;	%3B
<	%3C
=	%3D
>	%3E
?	%3F
@	%40
A	%41
B	%42
C	%43
D	%44
E	%45
F	%46
G	%47
H	%48
I	%49
J	%4A
K	%4B
L	%4C
M	%4D
N	%4E
O	%4F
P	%50
Q	%51
R	%52
S	%53
T	%54
U	%55
V	%56
W	%57
X	%58
Y	%59
Z	%5A
[	%5B
\	%5C
]	%5D
^	%5E
_	%5F
`	%60
a	%61
b	%62
c	%63
d	%64
e	%65
f	%66
g	%67
h	%68
i	%69
j	%6A
k	%6B
l	%6C
m	%6D
n	%6E
o	%6F
p	%70
q	%71
r	%72
s	%73
t	%74
u	%75
v	%76
w	%77
x	%78
y	%79
z	%7A
{	%7B
\|	%7C
}	%7D
~	%7E
	%7F
€	%80
	%81
‚	%82
ƒ	%83
„	%84
…	%85
†	%86
‡	%87
ˆ	%88
‰	%89
Š	%8A
‹	%8B
Œ	%8C
	%8D
Ž	%8E
	%8F
	%90
‘	%91
’	%92
“	%93
”	%94
•	%95
–	%96
—	%97
˜	%98
™	%99
š	%9A
›	%9B
œ	%9C
	%9D
ž	%9E
Ÿ	%9F
	%A0
¡	%A1
¢	%A2
£	%A3
	%A4
¥	%A5
\|	%A6
§	%A7
¨	%A8
©	%A9
ª	%AA
«	%AB
¬	%AC
¯	%AD
®	%AE
¯	%AF
°	%B0
±	%B1
²	%B2
³	%B3
´	%B4
µ	%B5
¶	%B6
·	%B7
¸	%B8
¹	%B9
º	%BA
»	%BB
¼	%BC
½	%BD
¾	%BE
¿	%BF
À	%C0
Á	%C1
Â	%C2
Ã	%C3
Ä	%C4
Å	%C5
Æ	%C6
Ç	%C7
È	%C8
É	%C9
Ê	%CA
Ë	%CB
Ì	%CC
Í	%CD
Î	%CE
Ï	%CF
Ð	%D0
Ñ	%D1
Ò	%D2
Ó	%D3
Ô	%D4
Õ	%D5
Ö	%D6
	%D7
Ø	%D8
Ù	%D9
Ú	%DA
Û	%DB
Ü	%DC
Ý	%DD
Þ	%DE
ß	%DF
à	%E0
á	%E1
â	%E2
ã	%E3
ä	%E4
å	%E5
æ	%E6
ç	%E7
è	%E8
é	%E9
ê	%EA
ë	%EB
ì	%EC
í	%ED
î	%EE
ï	%EF
ð	%F0
ñ	%F1
ò	%F2
ó	%F3
ô	%F4
õ	%F5
ö	%F6
÷	%F7
ø	%F8
ù	%F9
ú	%FA
û	%FB
ü	%FC
ý	%FD
þ	%FE
ÿ	%FF

URL Encoding Reference

The ASCII device control characters -%1f were originally designed to control
hardware devices. Control characters have nothing to do inside a URL.

ASCII Character	Description	URL-encoding
NUL	null character
SOH	start of header	%01
STX	start of text	%02
ETX	end of text	%03
EOT	end of transmission	%04
ENQ	enquiry	%05
ACK	acknowledge	%06
BEL	bell (ring)	%07
BS	backspace	%08
HT	horizontal tab	%09
LF	line feed	%0A
VT	vertical tab	%0B
FF	form feed	%0C
CR	carriage return	%0D
SO	shift out	%0E
SI	shift in	%0F
DLE	data link escape	%10
DC1	device control 1	%11
DC2	device control 2	%12
DC3	device control 3	%13
DC4	device control 4	%14
NAK	negative acknowledge	%15
SYN	synchronize	%16
ETB	end transmission block	%17
CAN	cancel	%18
EM	end of medium	%19
SUB	substitute	%1A
ESC	escape	%1B
FS	file separator	%1C
GS	group separator	%1D
RS	record separator	%1E
US	unit separator	%1F

Row Created Example

2009-06-09T05:23:00.000-07:00

For this example I've used Northwind as backend and the table is products

Source:



<asp:gridview id="GridView1" runat="server" autogeneratecolumns="False" datakeynames="ProductID" datasourceid="SqlDataSource1" cellpadding="4" forecolor="#333333" gridlines="None" onselectedindexchanged="GridView1_SelectedIndexChanged" onrowcreated="GridView1_RowCreated">
            <columns>
                <asp:BoundField DataField="ProductID" HeaderText="ProductID" InsertVisible="False"
                    ReadOnly="True" SortExpression="ProductID" />
                <asp:boundfield datafield="ProductName" headertext="ProductName" sortexpression="ProductName">
                <asp:boundfield datafield="CategoryID" headertext="CategoryID" sortexpression="CategoryID">
                <asp:boundfield datafield="SupplierID" headertext="SupplierID" sortexpression="SupplierID">
                <asp:boundfield datafield="QuantityPerUnit" headertext="QuantityPerUnit" sortexpression="QuantityPerUnit">
                <asp:boundfield datafield="UnitPrice" headertext="UnitPrice" sortexpression="UnitPrice">
                <asp:boundfield datafield="UnitsOnOrder" headertext="UnitsOnOrder" sortexpression="UnitsOnOrder">
            </columns>
            <rowstyle backcolor="#EFF3FB">
            <footerstyle backcolor="#507CD1" bold="True" forecolor="White">
            <pagerstyle backcolor="#2461BF" forecolor="White" horizontalalign="Center">
            <selectedrowstyle backcolor="#D1DDF1" bold="True" forecolor="#333333">
            <headerstyle backcolor="#507CD1" bold="True" forecolor="White">
            <editrowstyle backcolor="#2461BF">
            <alternatingrowstyle backcolor="White">
        </asp:GridView>
        <asp:sqldatasource id="SqlDataSource1" runat="server" connectionstring="">"
            SelectCommand="SELECT [ProductID], [ProductName], [CategoryID], [SupplierID], [QuantityPerUnit], [UnitPrice], [UnitsOnOrder] FROM [Products]">
        </asp:SqlDataSource>

Code behind page :


protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            //Get Price from the row

            decimal price;
            price = Convert.ToDecimal(DataBinder.Eval(e.Row.DataItem, "UnitPrice"));

            //Changing the cell color, by giving a condition

            if (price > 50)
            {
                e.Row.BackColor = System.Drawing.Color.Blue;
                e.Row.ForeColor = System.Drawing.Color.White;
                e.Row.Font.Bold = true;
            }
        }
    }

cheers

2008-06-16T07:16:00.000-07:00

This junk of code about to display populating data on the GridView

Here
I've taken GridView to display the data
SqlDataSource to connect the database
BulletList to populate Territories

The DataBase is NorthWind

< asp:GridView ID="employeesGridView" Runat="server" DataSourceID="employeesDataSource"
AutoGenerateColumns="False" BorderWidth="1px" BackColor="White" GridLines="Horizontal"
CellPadding="3" BorderStyle="None" BorderColor="#E7E7FF" OnRowDataBound="employeesGridView_RowDataBound">
< FooterStyle ForeColor="#4A3C8C" BackColor="#B5C7DE">< /FooterStyle>
< PagerStyle ForeColor="#4A3C8C" HorizontalAlign="Right" BackColor="#E7E7FF">< /PagerStyle>
< HeaderStyle ForeColor="#F7F7F7" Font-Bold="True" BackColor="#4A3C8C">< /HeaderStyle>
< AlternatingRowStyle BackColor="#F7F7F7">< /AlternatingRowStyle>
< Columns>
< asp:BoundField HeaderText="LastName" DataField="LastName" SortExpression="LastName">< /asp:BoundField>
< asp:BoundField HeaderText="FirstName" DataField="FirstName" SortExpression="FirstName">< /asp:BoundField>
< asp:TemplateField HeaderText="Territories">< ItemTemplate>
< asp:BulletedList ID="bltTerritories" Runat="server" DataTextField="TerritoryDescription"
DataValueField="TerritoryDescription">
< /asp:BulletedList>
< /ItemTemplate>
< /asp:TemplateField>
< /Columns>
< SelectedRowStyle ForeColor="#F7F7F7" Font-Bold="True" BackColor="#738A9C">< /SelectedRowStyle>
< RowStyle ForeColor="#4A3C8C" BackColor="#E7E7FF">< /RowStyle>
< /asp:GridView>

< asp:SqlDataSource ID="employeesDataSource" Runat="server" SelectCommand="SELECT [EmployeeID], [LastName], [FirstName] FROM [Employees] ORDER BY [LastName], [FirstName]"
ConnectionString="< %$ ConnectionStrings:NWConnectionString %>">
< /asp:SqlDataSource>
< asp:SqlDataSource ID="territoriesDataSource" Runat="server" SelectCommand="SELECT dbo.EmployeeTerritories.EmployeeID, dbo.Territories.TerritoryDescription FROM dbo.Territories INNER JOIN dbo.EmployeeTerritories ON dbo.Territories.TerritoryID = dbo.EmployeeTerritories.TerritoryID"
ConnectionString="< %$ ConnectionStrings:NWConnectionString %>">
< /asp:SqlDataSource>

void employeesGridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
// For each DataRow in the GridView, programmatically access the BulletedList, filter
// the DataView based on the GridView row's EmployeeID value and bind the filtered DataView
// to the BulletedList
if (e.Row.RowType == DataControlRowType.DataRow)
{
BulletedList bl = (BulletedList)e.Row.FindControl("bltTerritories");
territoryData.RowFilter = "EmployeeID = " + ((DataRowView) e.Row.DataItem)["EmployeeID"].ToString();
bl.DataSource = territoryData;
bl.DataBind();
}
}

DataView territoryData; // this DataView will hold all of the Territories, loaded at Page_Load

void Page_Load(object sender, EventArgs e)
{
// Load all of the territories into a DataView from the SqlDataSource
territoryData = (DataView)territoriesDataSource.Select(DataSourceSelectArguments.Empty);
}

--
Cheers
Enjoy the coding

Abstract Classes

2008-05-15T13:07:00.000-07:00

This is a detailed analysis of Abstract classes and methods in C# with some concrete examples.

The keyword abstract can be used with both classes and methods in C# to declare them as abstract.

The classes, which we can't initialize, are known as abstract classes. They provide only partial implementations. But another class can inherit from an abstract class and can create their instances.

For example, an abstract class with a non-abstract method.

using System;
abstract class MyAbs
{
public void NonAbMethod()
{
Console.WriteLine("Non-Abstract Method");
}
}
class MyClass : MyAbs
{
}
class MyClient
{
public static void Main()
{
//MyAbs mb = new MyAbs();//not possible to create an instance
MyClass mc = new MyClass();
mc.NonAbMethod(); // Displays 'Non-Abstract Method'
}
}

An abstract class can contain abstract and non-abstract methods. When a class inherits from an abstract, the derived class must implement all the abstract methods declared in the base class.

An abstract method is a method without any method body. They are implicitly virtual in C#.

using System;
abstract class MyAbs
{
public void NonAbMethod()
{
Console.WriteLine("Non-Abstract Method");
}
public abstract void AbMethod(); // An abstract method
}
class MyClass : MyAbs//must implement base class abstract methods
{
public override void AbMethod()
{
Console.WriteLine("Abstarct method");
}
}
class MyClient
{
public static void Main()
{
MyClass mc = new MyClass();
mc.NonAbMethod();
mc.AbMethod();
}
}

But by declaring the derived class also abstract, we can avoid the implementation of all or certain abstract methods. This is what is known as partial implementation of an abstract class.

using System;
abstract class MyAbs
{
public abstract void AbMethod1();
public abstract void AbMethod2();
}
//not necessary to implement all abstract methods
//partial implementation is possible
abstract class MyClass1 : MyAbs
{
public override void AbMethod1()
{
Console.WriteLine("Abstarct method #1");
}
}
class MyClass : MyClass1
{
public override void AbMethod2()
{
Console.WriteLine("Abstarct method #2");
}
}
class MyClient
{
public static void Main()
{
MyClass mc = new MyClass();
mc.AbMethod1();
mc.AbMethod2();
}
}

In C#, an abstract class can inherit from another non-abstract class. In addition to the methods it inherited from the base class, it is possible to add new abstract and non-abstract methods as showing below.

using System;
class MyClass1 // Non-Abstract class
{
public void Method1()
{
Console.WriteLine("Method of a non-abstract class");
}
}
abstract class MyAbs : MyClass1 // Inherits from an non-abstract class
{
public abstract void AbMethod1();
}
class MyClass : MyAbs//must implement base class abstract methods
{
public override void AbMethod1()
{
Console.WriteLine("Abstarct method #1 of MyClass");
}
}
class MyClient
{
public static void Main()
{
MyClass mc = new MyClass();
mc.Method1();
mc.AbMethod1();
}
}

An abstract class can also implement from an interface. In this case we must provide method body for all methods it implemented from the interface.

using System;
interface IInterface
{
void Method1();
}
abstract class MyAbs : IInterface
{
public void Method1()
{
Console.WriteLine("Method implemented from the IInterface");
}
}
class MyClass : MyAbs//must implement base class abstract method
{
}
class MyClient
{
public static void Main()
{
MyClass mc = new MyClass();
mc.Method1();
}
}
}
}

We can't use the key word abstract along with sealed in C#, since a sealed class can't be abstract.

The abstract methods are implicitly virtual and hence they can't mark explicitly virtual in C#.

For example

using System;
abstract class MyAbs
{
public abstract void AbMethod1();
public abstract void AbMethod2();
}
class MyClass1 : MyAbs
{
public override void AbMethod1(){
Console.WriteLine("Abstarct method #1 of MyClass1");
}
public override void AbMethod2()
{
Console.WriteLine("Abstarct method #2 of MyClass1");
}
}
class MyClient
{
public static void Main()
{
MyAbs ma1 = new MyClass1();// Polymorphism
ma1.AbMethod1();
ma1.AbMethod2();
}
}

Virtual Classes

2008-05-15T13:03:00.000-07:00

Methods, properties, and indexers can be virtual, which means that their implementation can be overridden in derived classes.
The example: using System;
class CAbc
{
public virtual void F() { Console.WriteLine("CAbc.F"); }
}
class CBcd: CAbc
{
public override void F() {
base.F();
Console.WriteLine("CBcd.F");
}
}
class Test
{
static void Main() {
CBcd b = new CBcd();
b.F();
CAbc a = b;
a.F();
}
}
This shows a class CAbc with a virtual method F, and a class CBcd that overrides F. The overriding method in B contains a call base.F() which calls the overridden method in A.

Sealed Classes

2008-05-15T12:57:00.000-07:00

Sealed Classes

The sealed modifier is used to prevent derivation from a class. An error occurs if a sealed class is specified as the base class of another class. A sealed class cannot also be an abstract class.
The sealed modifier is primarily used to prevent unintended derivation, but it also enables certain run-time optimizations. In particular, because a sealed class is known to never have any derived classes, it is possible to transform virtual function member invocations on sealed class instances into non-virtual invocations.
In C# structs are implicitly sealed; therefore, they cannot be inherited. using System;
sealed class MyClass
{
public int x;
public int y;
}
class MainClass
{
public static void Main()
{
MyClass mC = new MyClass();
mC.x = 110;
mC.y = 150;
Console.WriteLine("x = {0}, y = {1}", mC.x, mC.y);
}
}
In the preceding example, if you attempt to inherit from the sealed class by using a statement like this:
class MyDerivedC: MyClass {} // Error
You will get the error message:'MyDerivedC' cannot inherit from sealed class 'MyBaseC'.
In C# a method can't be declared as sealed. However when we override a method in a derived class, we can declare the overrided method as sealed as shown below. By declaring it as sealed, we can avoid further overriding of this method. using System;
class MyClass1
{
public int x;
public int y;
public virtual void Method()
{
Console.WriteLine("virtual method");
}
}
class MyClass : MyClass1
{
public override sealed void Method()
{
Console.WriteLine("sealed method");
}
}
class MainClass
{
public static void Main()
{
MyClass1 mC = new MyClass();
mC.x = 110;
mC.y = 150;
Console.WriteLine("x = {0}, y = {1}", mC.x, mC.y);
mC.Method();
}
}
Conclusion

SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified

2008-05-05T07:34:00.000-07:00

Users often see this error message when connection to a SQL Server and don't know where to start to solve the problem. In most forums, people says this is because remote connection is not enabled on the server. This is not exactly correct. Actually, this error message give customers very specific information and the solution is quite simple.

First of all, you get this error message only if you are trying to connect to a SQL Server named instance. For default instance, you never see this. Why? Because even if we failed at this stage (i.e. error locating server/instance specified), we will continue to try connect using default values, e.g defaul TCP port 1433, default pipe name for Named Pipes. You may see other error message due to failure later, but not this error message.

Every time client makes a connection to SQL Server named instance, we will send a SSRP UDP packet to the server machine UDP port 1434. We need this step to know configuration information of the SQL instance, e.g., protocols enabled, TCP port, pipe name etc. Without these information, client does know how to connect the server and it fails with this specified error message.

In a word, the reason that we get this error message is the client stack could not receive SSRP response UDP packet from SQL Browser. It's easy to isolate the issue. Here are the steps:
1) Make sure your server name is correct, e.g., no typo on the name.
2) Make sure your instance name is correct and there is actually such an instance on your target machine. [Update: Some application converts \\ to \. If you are not sure about your application, please try both Server\Instance and Server\\Instance in your connection string]
3) Make sure the server machine is reachable, e.g, DNS can be resolve correctly, you are able to ping the server (not always true).
4) Make sure SQL Browser service is running on the server.
5) If firewall is enabled on the server, you need to put sqlbrowser.exe and/or UDP port 1434 into exception.

Once you are done the steps, you should not see this error message anymore. You may still fail to connect your SQL server, but error message should be different and you have a different issue now. [Update: If it still fails, you may replace server\instance with tcp:server\instance and/or np:server\instance and see if it succeeds with either TCP or NP protocol. That way, you can isolate the issue a little bit. ]

There is one corner case where you may still fail after you checked step 1)-4). It happens when a) your server is a named instance on cluster or on a multi-homed machine, and b) your client is a Vista machine with Firewall on. I have explained the details at: Unable to connect to a SQL Server named instance on a cluster

As a final note, the error message for the same issue when you use SNAC is:
[SQL Native Client]SQL Network Interfaces: Error Locating Server/Instance Specified [xFFFFFFFF].

If you still see this error, please post questions at MSDN SQL Server Data Access Forum:
http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=87&SiteID=1
Please mention you already read this post and confirm steps you have taken and the results of each step.(e.g. server\instance,etc)

2008-01-14T05:28:00.000-08:00

The SHA1 algorithm can be used to calculate check sum, that very useful when you want to ensure the string is not broken .Also for simple password verification.The example below show how to calculate SHA1 for given string .

///


/// Calculates SHA1 hash
///


/// input string
/// Character encoding
/// SHA1 hash

public static string CalculateSHA1(string text, Encoding enc)
{
byte[] buffer = enc.GetBytes(text);
SHA1CryptoServiceProvider cryptoTransformSHA1 =
new SHA1CryptoServiceProvider();
string hash = BitConverter.ToString(
cryptoTransformSHA1.ComputeHash(buffer)).Replace("-", "");
return hash;

}

The result SHA1 hash for the string "first string":