Contracts in WCF Service

 Contracts in WCF Service 

Contracts are useful for building WCF service applications. They define what the protocol (binding) the service uses, how the communication will be done, what message exchange format to use and so on.

 

The following are the contracts are available in WCF:

• Service contracts
• Data Contracts
• Message contracts
• Fault Contract
• Operation Contract

Service contracts

 

Service contracts define the Interface for the service. It can be defined as follows.

 

Syntax

1. [ServiceContract]  
2. public interface IService1  
3. {  
4.  
5.     // TODO: Add your service operations here  
6. } 
   

Key Points

• Any WCF service can have more than one service contract.
• Declare at least one service contract in a service.
• A service contract can be declared using the [ServiceContract] attribute.
• It allows defining an Operation Contract under it to expose the service outside the world.
• It maps the interface and methods of your service to a platform-independent description.
• It describes message exchange patterns that the service can have with another party. Some service operations might be one-way, others might require a request-reply pattern.

The service contract attribute has the following properties:

• CallbackContract
• ConfigurationName
• HasProtectionLevel
• Name
• Namespace
• ProtectionLevel
• SessionMode
• TypeId

Operation Contract

 

An Operation Contract defines the method exposed to the client to exchange the information between the client and server. An Operation Contract describes what functionality is to be given to the client, such as addition, subtraction and so on.

 

It can be defined as in the following:

1. public interface IService1  
2. {  
3.     [OperationContract]  
4.     string GetData(int value);  
5.   
6.     [OperationContract]  
7.     CompositeType GetDataUsingDataContract(CompositeType composite);  
8.     
9. } 
   

The Operation Contract attribute has the following properties:

• CallbackContract: Gets or sets the type of callback contract when the contract is a duplex contract.
  
• ConfigurationName: Gets or sets the name used to locate the service in an application configuration file.
  
• HasProtectionLevel: Gets a value that indicates whether the member has a protection level assigned.
  
• Name: Gets or sets the name of the <portType> element in the Web Services Description Language (WSDL).
  
• Namespace: Gets or sets the namespace of the <portType> element in the Web Services Description Language (WSDL).
  
• ProtectionLevel: Specifies whether the binding for the contract must support the value of the ProtectionLevel property.
  
• SessionMode: Gets or sets whether sessions are allowed, not allowed or required.
  
• TypeId: When implemented in a derived class, gets a unique identifier for this Attribute.

Data Contract

 

Data Contracts define the data type for variables that are the same as get and set properties but the difference is that a Data Contract in WCF is used to serialize and deserialize the complex data. It defines how data types are serialized and deserialized. Using serialization, you can convert an object into a sequence of bytes that can be transmitted over a network. Using de-serialization, you reassemble an object from a sequence of bytes that you receive from a calling application.

 

It can be defined as follows:

1. [DataContract]  
2. public class Student  
3. {  
4.     private string _Name;  
5.   
6.     private string _City;  
7.   
8.   
9.     [DataMember]  
10.     public string Name  
11.     {  
12.         get { return _Name; }  
13.         set { _Name = value; }  
14.     }  
15. } 
    

Fault Contract

 

A Fault Contract handles the exception and understands the cause of the error that occurs in the WCF service. When we develop a managed application or service, we will handle the exception using a try- catch block, but these exceptions handlers are technology-specific.

 

The following is the syntax to raise the custom error in WCF:

1. [ServiceContract]  
2. public interface IGetDetailsService  
3. {  
4.      [OperationContract]  
5.      [FaultContract(typeof(Student))]  
6.      Student GetDetails(string Name);  
7. }  
8.   
9. [DataContract]  
10. public class Student  
11. {  
12.      private string _Name;  
13.   
14.      private string _City;  
15.   
16.      [DataMember]  
17.      public string Name  
18.      {  
19.          get { return _Name; }  
20.          set { _Name = value; }  
21.      }  
22.   
23.      [DataMember]  
24.      public string City  
25.      {  
26.          get { return _City; }  
27.          set { _City = value; }  
28.      }  
29. } 
    

Message contracts

 

The default SOAP message format is provided by the WCF runtime for communication between the client and the service. If it does not meet your requirements then we can create our own message format. This can be done using the Message Contract attribute.

 

It can be defined as:

1. [MessageContract]  
2. public class Person  
3. {  
4.    [MessageHeader] public Operation Name;  
5.    [MessageHeader] public string city;  
6.    [MessageBodyMember] private Home Address;  
7.    [MessageBodyMember] private Home Streat;  
8.    [MessageBodyMember] public int age;  
9. } 
   

Note

 

Please refer to the following articles for a complete understanding:

• Introduction to WCF Service
• Creating WCF Service
• End Points in WCF
• Ajax Enabled WCF Service
• Binding In WCF Service
• Consuming WCF Service in Web Application

Summary

 

I hope this article is useful for all students and beginners. Happy Learning , i have refer this Article from Mr Vithal Wadje

The Angular CLI requires a minimum Node.js version of either

 

The Angular CLI requires a minimum Node.js version of either

The error "The Angular CLI requires a minimum Node.js version of either" occurs when your Node.js version is not supported by the Angular CLI.

To solve the error, install the long-term supported version of Node.

You can use the node -v command to check your version of Node.js.

if you saw in error it is indicate current node version is 20.15 but it is not supporting so we have to upgrade Node version -

So we have to upgrade node-v22.17.0-x64 ( You can use node version according to you angular version ).

Thank you when you update the version this issue is fixed.

Thank you Hope it is help you !  

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Dear Developer,

When starting a new project in Visual Studio and you want to connect it to source control, here’s what you need to do:

Take a look at the window below:

1st you have to download and install the Gits for window(I am using window os you can manage according to your OS) the URL is https://git-scm.com/downloads/win

Then, refer to the first screen and click the Reload link. You should see a screen like the one below:

Thank you! I hope this was helpful to you.

Unable to find packages "PackageName". No packages exist with this id in source(s): C:\Program Files\dotnet\library-packs, Microsoft Visual Studio Offline Packages

 Hello Everyone,

Sometimes, when you clone your code to a new location and try to run it, you might encounter an error like:

Unable to find package "PackageName". No packages exist with this ID in source(s): C:\Program Files\dotnet\library-packs, Microsoft Visual Studio Offline Packages

Don’t worry — this is a common issue, and the solution is simple. Just follow the steps below to resolve it.

✅ Here's how to fix it:

1. Add nuget.org as a Package Source

Visual Studio might not be configured to look at the official NuGet repository. To fix this:

1. Go to Tools > Options.
2. Navigate to NuGet Package Manager > Package Sources.
3. Click the "+" button to add a new source.
4. Set:
   • Name: nuget.org
   • Source: https://api.nuget.org/v3/index.json
5. Click Update or OK to save.

Make sure nuget.org is checked and at the top of the list 

your setting look like as below screen.

Rebuild your solution ! Hope it help you 

Thank you!