Introduction
WCF is an abbreviation for Windows Communication Foundation. It is a service-oriented application framework and is mostly employed in developing a distributed and interoperable application. You can communicate data as asynchronous messages from one service endpoint to another using WCF. WCF Applications first appeared in the.Net 3.0 Framework.
WCF is built entirely on the.NET framework. It is typically implemented as a set of classes in the.NET framework corresponding to the CLR. WCF, on the other hand, enables.NET application developers to create service-oriented applications. It addresses the issue of interoperability in distributed applications using. NET. To communicate with the server, the WCF client employs the Simple Object Access Protocol (SOAP). The operating system, hardware, and programming platform are unimportant to the client and server, and communication occurs at a high degree of abstraction.
WCF Interview Questions for Freshers
1.What is WCF?
WCF is a service-oriented application framework and is mostly employed in developing a distributed and interoperable application. You can communicate data as asynchronous messages from one service endpoint to another using WCF. A service client can be an endpoint that requests data from a service endpoint. It allows you to develop more secure, flexible services without changing code. It also has built-in logging functionality. It enables and disables logging through settings.
2. What are the main components used in WCF?
There are mainly three essential components in WCF:
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Service class
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Endpoint
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Hosting Environment
3. What is the "Address" property of the endpoint in WCF?
The "Address" property is a service-level endpoint property. This field is used to indicate the service's location.
4. What is the service in WCF?
A service is a set of functionality that is exposed to the outside world. Service orientation (SO) is a general term for a set of concepts and best practices for developing service-oriented applications.
5. What are the various instance modes in WCF?
The different instance modes in WCF are the following:
- Per Call
- Singleton
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Per Session
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6. What are the various benefits or advantages of WCF Technology?
There are the following advantages of WCF Technology:
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The framework can be customized to work with either SOAP or RSS.
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This is a common communication technology that performs better when compared to other Microsoft specs.
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This architecture is appropriate for a secure connection, data transmission, and even speed optimization. It exchanges data in binary format to reduce latency.
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This distributed management solution is suitable for practically all WCF-based applications.
7. Explain what the difference between ASMX web services and WCF is.
The primary distinction between WCF and ASMX or ASP.NET web services is that ASMX is meant to transmit and receive messages only via SOAP over HTTP. In comparison, the WCF can send messages in any format via any transport protocol.
8. What is WCF ABC?
In WCF ABC stands for Address, Billing, and Contract.
9. How many types of contracts does WCF define?
There are mainly four types of contracts does WCF defines as follows:
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Contracts for Services
The ServiceContract attribute connects a CLR interface (or inferred interface, as we'll learn later) to a technology-independent service contract. The ServiceContract property exposes a CLR interface (or a class) as a WCF contract, regardless of the visibility.
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Data Contracts
The metadata descriptions of the data types that the service utilizes. This allows people to interact with the service. The data types can be used anywhere in a message, such as arguments or return types. There is no need to employ data contracts explicitly if the service just uses simple types.
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Fault Contracts
Errors that can be returned to the caller can be associated with a service action.
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Message Contracts
Describes a message's format. It specifies, whether message elements should be placed in headers or the body, what level of security should be given to which message elements, and so on.
10. What are the features and advantages of WCF?
The features of WCF are as follows:
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Service Orientation
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Interoperability
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Multiple Message Patterns
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Service Metadata
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Reliable and Queued Messages
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Data Contracts
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Security
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Multiple modes of transport and Encodings
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Durable Messages
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Transactions
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Extensibility
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AJAX and REST Support
Advantages of WCF:
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Service Oriented
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Location Independent
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Language Independent
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It can control concurrency
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Support Multiple operations
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It can maintain state
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Platform Independent
- It can be hosted on IIS, WAS, Self-hosting, and Windows services.
11. What are standard Endpoints?
WCF provides a collection of pre-defined endpoints referred to as Standard Endpoints for metadata sharing, discovery, and web services. The standard endpoints can be configured using a config file or programmatically. The following is a list of standard endpoints:
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mexEndpoint
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webHttpEndpoint
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webScriptEndpoint
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workflowControlEndpoin
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announcementEndpoint
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discoveryEndpoint
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udpAnnouncementEndpoint
- udpDiscoveryEndpoint
12. Explain the fundamentals of WCF.
The Windows Communication Foundation (WCF) is a framework for developing service-oriented applications that allow us to transfer asynchronous messages/data from one service endpoint to another.
WCF is a runtime and API set for building systems that deliver messages between services and clients. The same infrastructure and APIs are used to develop apps that connect with other programs on the same computer system or on a system hosted by another firm and accessible over the Internet.
The WCF fundamentals are as follows:
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Unification
- COM+ Services
- Web Services
- .NET Remoting
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Microsoft Message Queuing
- Interoperability
- Service Orientation
13. Explain the architecture of WCF.
A new service-oriented programming approach is available to developers in four main tiers. The following layers make up the WCF architecture.
14. What is a Service Contract in WCF?
A Service Contract in WCF is an interface marked with the [ServiceContract] attribute. It defines the operations that a WCF service can perform. Methods within this interface are marked with the [OperationContract] attribute.
15. What is the difference between BasicHttpBinding and WSHttpBinding in WCF?
- BasicHttpBinding: Used for simple, unsecured services with HTTP protocol and XML-based messaging, suitable for web services.
- WSHttpBinding: Provides more advanced features such as security, reliability, and transactions, often used for secure communication in enterprise applications.
16. What is the difference between a one-way operation and a request-reply operation in WCF?
A one-way operation, marked with [OperationContract(IsOneWay = true)], doesn't return a value and the client doesn't wait for a response. A request-reply operation, which is the default, returns a value and the client waits for the response.
17. How do you define a service contract in WCF?
A service contract is defined using the [ServiceContract] and [OperationContract] attributes. Example:
[ServiceContract]
public interface ICalculator
{
[OperationContract]
int Add(int a, int b);
}18. What are the different ways to host a WCF service?
WCF services can be hosted in:
- IIS (Internet Information Services)
- Windows Activation Service (WAS)
- Self-hosting (in a console application or Windows service)
- AppFabric
19. How do you handle exceptions in WCF?
Exceptions in WCF are handled using Fault Contracts. The [FaultContract] attribute is used to specify custom error messages that can be sent to the client in the event of an exception.
20. What is an Endpoint in WCF?
An Endpoint in WCF is the place where a client can communicate with a service. It consists of three parts:
- Address: Where the service is located
- Binding: How to communicate with the service
- Contract: What operations the service can perform
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