What are the types of binding available in WCF?
A binding is identified by the transport it supports and the encoding it uses. Transport may be HTTP,TCP etc and encoding may be text,binary etc. The popular types of binding may be as below:
a)BasicHttpBinding
b)NetTcpBinding
c)WSHttpBinding
d)NetMsmqBinding
a)BasicHttpBinding
b)NetTcpBinding
c)WSHttpBinding
d)NetMsmqBinding
What are the types of contract available in WCF?
The main contracts are:
a)Service Contract:Describes what operations the client can perform.
b)Operation Contract : defines the method inside Interface of Service.
c)Data Contract:Defines what data types are passed
d)Message Contract:Defines wheather a service can interact directly with messages
a)Service Contract:Describes what operations the client can perform.
b)Operation Contract : defines the method inside Interface of Service.
c)Data Contract:Defines what data types are passed
d)Message Contract:Defines wheather a service can interact directly with messages
What are the various ways of hosting a WCF Service?
a)IIS b)Self Hosting c)WAS (Windows Activation Service)
What is the proxy for WCF Service?
A proxy is a class by which a service client can Interact with the service.
By the use of proxy in the client application we are able to call the different methods exposed by the service
How can we create Proxy for the WCF Service?
What is the difference between WCF Service and Web Service?We can create proxy using the tool svcutil.exe after creating the service.
We can use the following command at command line.
svcutil.exe *.wsdl *.xsd /language:C# /out:SampleProxy.cs /config:app.config
We can use the following command at command line.
svcutil.exe *.wsdl *.xsd /language:C# /out:SampleProxy.cs /config:app.config
a)WCF Service supports both http and tcp protocol while webservice supports only http protocol.
b)WCF Service is more flexible than web service.
b)WCF Service is more flexible than web service.
Which specifications does WCF follow?WCF supports specifications defined by WS-* specifications. WS-* specifications are defined
together by Microsoft, IBM, SUN and many other big companies so that they can expose there
service through a common protocol. WCF supports all specifications defined we will understand
them one by one.
• Messaging (WS-Addressing):- SOAP is the fundamental protocol for web services. WS
Addressing defines some extra additions to SOAP headers, which makes SOAP free from
underlying transport protocol. One of the good things about Message transmission is MTOM,
also termed as Message Transmission Optimization Mechanism. They optimize transmission
format for SOAP messages in XML-Binary formant using XML optimized packaging (XOP).
Because the data will sent in binary and optimized format, it will give us huge performance
gain.
• Security (WS-Security, WS-Trust, and WS-Secure Conversation): All the three WSdefine
authentication, security, data integrity and privacy features for a service.
• Reliability (WS-Reliable Messaging): This specification ensures end-to-end
communication when we want SOAP messages to be traversed back and forth many times.
• Transactions (WS-Coordination and WS-Atomic Transaction): These two specifications
enable transaction with SOAP messages.
• Metadata (WS-Policy and WS-Metadata exchange): WSDL is a implementation of WSMetadata
Exchange protocol. WS-Policy defines more dynamic features of a service, which
cannot be expressed by WSDL.
WCF follows WS-* specifications other
languages like JAVA , C++ can also exploit features like Messaging , Security , Reliability and
transactions written in C# or VB.NET. This is the biggest achievement of WCF to integrate the
above features with other languages.
What is the difference WCF and Web services?
Web services can only be invoked by HTTP. While Service or a WCF component can be invoked
by any protocol and any transport type. Second web services are not flexible. However, 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.
what are the advantages of hosting WCF Services in IIS as compared to self-hosting?There are two main advantages of using IIS over self-hosting:-
Automatic activation
IIS provides automatic activation that means the service is not necessary to be running in
advance. When any message is received by the service it then launches and fulfills the request.
But in case of self hosting the service should always be running.
Process recyclingIf IIS finds that a service is not healthy that means if it has memory leaks etc, IIS recycles the
process. For every browser instance, a worker process is spawned and the request is serviced. When the browser disconnects the worker, process stops and you loose all information. IIS also restarts the worker process. By default, the worker process is recycled at around 120 minutes. So why does IIS recycle. By restarting the worker process it ensures any bad code or memory leak do not cause issue to the whole system.
In case of self-hosting both the above features, you will need to code yourself. Lot of work
right!!.
what are the various ways of hosting a WCF service?
There are three major ways to host 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 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.
Which are the various programming approaches for WCF?/ What is one-way operation?IsOneWay equal to true ensures that the client does not have to wait for the response. So methods
marked by IsOneWay to true should always return void. In this, the caller does not get anything
in return so it is called as one-way communication
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.
This binding is used when we need to use SOAP over HTTP. This binding
can also be configured to be used as HTTPS. It can be also configured to send data in plain text or
in optimized form like MTOM.
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.
This binding sends binary-encoded SOAP, including support for reliable
message transfer, security, and transactions, directly over TCP. The biggest disadvantage of
NetTcpBinding is that both server and client should be also made in .NET language.
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.
It is same like BasicHttpBinding. In short, it uses SOAP over HTTP. But with
it also supports reliable message transfer, security and transaction. WS-Reliable Messaging,
security with WS-Security, and transactions with WS-Atomic Transaction supports reliable
message.
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.
This binding sends binary-encoded SOAP over MSMQ. This binding can
only be used for WCF-to-WCF communication
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 |
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 |
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>
|
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. |
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 |
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. |
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);
}
|
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 |
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 |
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>
|
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. |
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 |
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. |
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);
}
|
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 |
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 |
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>
|
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. |
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 |
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. |
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);
}
|
ServiceBehaviour attribute is used to specify the InstanceContextMode for the WCF Service class (This can be used to maintained a state of the service or a client too)
There are three instance Context Mode in the WFC
PerSession : This is used to create a new instance for a service and the same instance is used for all method for a particular client. (eg: State can be maintained per session by declaring a variable)
PerCall : This is used to create a new instance for every call from the client whether same client or different. (eg: No state can be maintained as every time a new instance of the service is created)
Single : This is used to create only one instance of the service and the same instance is used for all the client request. (eg: Global state can be maintained but this will be applicable for all clients)
There are three instance Context Mode in the WFC
PerSession : This is used to create a new instance for a service and the same instance is used for all method for a particular client. (eg: State can be maintained per session by declaring a variable)
PerCall : This is used to create a new instance for every call from the client whether same client or different. (eg: No state can be maintained as every time a new instance of the service is created)
Single : This is used to create only one instance of the service and the same instance is used for all the client request. (eg: Global state can be maintained but this will be applicable for all clients)
WCF - Interview Questions with Answers
Windows Communication Foundation :Interview Questions with Answers
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. WCF is Microsoft's unified programming model for building service-oriented applications with managed code. It extends the .NET Framework to enable developers to build secure and reliable transacted Web services that integrate across platforms and interoperate with existing investments.
Windows Communication Foundation combines and extends the capabilities of existing Microsoft distributed systems technologies, including Enterprise Services, System.Messaging, Microsoft .NET Remoting, ASMX, and WSE to deliver a unified development experience across multiple axes, including distance (cross-process, cross-machine, cross-subnet, cross-intranet, cross-Internet), topologies (farms, fire-walled, content-routed, dynamic), hosts (ASP.NET, EXE, Windows Presentation Foundation, Windows Forms, NT Service, COM+), protocols (TCP, HTTP, cross-process, custom), and security models (SAML, Kerberos, X509, username/password, custom).
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.
What is endpoint in WCF? or What is three major points in WCF?
Every service must have Address that defines where the service resides, Contract that defines what the service does and a Binding that defines how to communicate with the service.
In WCF the relationship between Address, Contract and Binding is called Endpoint. The Endpoint is the fusion of Address, Contract and Binding.
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 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.
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. Federated WS binding :
Offered by the WSFederationHttpBinding class, this is a specialization of the WS binding, offering support for federated security.
7. 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.
8. MSMQ binding :
Offered by the NetMsmqBinding class, this uses MSMQ for transport and is designed to offer support for disconnected queued calls.
9. 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.
What is 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.
1. Service contracts : Describe which operations the client can perform on the service.
2. 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.
3. Fault contracts : Define which errors are raised by the service, and how the service handles and propagates errors to its clients.
4. 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.
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
1. HTTP
2. TCP
3. Peer network
4. IPC (Inter-Process Communication over named pipes)
5. 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
What is the difference WCF and Web services?
1. Web services can only be invoked by HTTP. While Service or a WCF component can be invoked by any protocol and any transport type.
2. Second web services are not flexible. But Services are flexible. If you make a new version of the service then you need to just expose a new end point. So services are agile and which is a very practical approach looking at the current business trends.
How can we host a service on two different protocols on a single server?
Let’s first understand what this question actually means. Let’s say we have made a service and we want to host this service using HTTP as well as TCP.
You must be wondering why to ever host services on two different types of protocol. When we host a service it’s consumed by multiple types of client and it’s very much possible that they have there own protocol of communication. A good service has the capability to downgrade or upgrade its protocol according the client who is consuming him.
Let’s do a small sample in which we will host the ServiceGetCost on TCP and HTTP protocol.
Once we are done the server side coding its time to see make a client by which we can switch between the protocols and see the results. Below is the code snippet of the client side for multi-protocol hosting
How does WCF work?
Follows the 'software as a service' model, where all units of functionality are defined as services.
A WCF Service is a program that exposes a collection of Endpoints. Each Endpoint is a portal (connection) for communication with either clients (applications) or other services.
Enables greater design flexibility and extensibility of distributed systems architectures.
A WCF application is represented as a collection of services with multiple entry points for communications.
What are the main components of WCF?
1.Service: The working logic or offering, implemented using any .Net Language(C).
2.Host: The environment where the service is parked. E.g. exe, process, windows service
3.Endpoints: The way a service is exposed to outside world.
Explain transactions in WCF.
Transactions in WCF allow several components to concurrently participate in an operation. Transactions are a group of operations that are atomic, consistent, isolated and durable. WCF has features that allow distributed transactions. Application config file can be used for setting transaction timeouts.
Messaging Pattern : Messaging patterns describes how client and server should exchange the message. There is a protocol between client and server for sending and receiving the message. These are also called Message Exchange Pattern. WCF supports following 3 types of Message Exchange Patterns 1. request - reply (default message exchange pattern) 2. OneWay (Simplex / datagram) 3. Duplex(CallBack) Thanks Prasham |
.svc file is a text file. This file is similar to our .asmx file in web services. This file contains the details required for WCF service to run it successfully. This file contains following details : 1. Language (C# / VB) 2. Name of the service 3. Where the service code resides Example of .svc file <%@ ServiceHost Language="C#/VB" Debug="true/false" CodeBehind="Service code files path" Service="ServiceName" We can also write our service code inside but this is not the best practice. |
The XML Information Set defines a data model for XML. It is an abstract set of concepts such as attributes and entities that can be used to describe a valid XML document. According to the specification, "An XML document's information set consists of a number of information items; the information set for any well-formed XML document will contain at least a document information item and several others." |
1.IIS 2.Self Hosting 3.WAS (Windows Activation Service) |
DataContractSerializer is new WCF serializer. This is serialization engine in WCF. DataContractSerializer translate the .NET framework objects into XML and vice-versa. By default WCF uses DataContractSeriazer. |
Message Contract : Message Contract is the way to control the SOAP messages, sent and received by the client and server. Message Contract can be used to add and to get the custom headers in SOAP message Because of Message Contract we can customize the parameters sent using SOAP message between the server and client. Thanks Prasham |
Fault Contracts is the way to handle exceptions in WCF. The problem with exceptions is that those are technology specific and therefore cannot be passed to other end because of interoperability issue. (Means either from Client to Server or vice-versa). There must be another way representing the exception to support the interoperability. And here the SOAP Faults comes into the picture. Soap faults are not specific to any particular technology and they are based on industry standards. To support SOAP Faults WCF provides FaultException class. This class has two forms: a. FaultException : to send untyped fault back to consumer b. FaultException<T>: to send typed fault data to the client WCF service also provides FaultContract attribute so that developer can specify which fault can be sent by the operation (method). This attribute can be applied to operations only. |
a. DataContractSerializer is the default serializer fot the WCF b. DataContractSerializer is very fast. c. DataContractSerializer is basically for very small, simple subset of the XML infoset. d. XMLSerializer is used for complex schemas. Thanks Prasham |
When multiple endpoints are associated with WCF service, base address (one primary address) is assigned to the service, and relative addresses are assigned to each endpoint. Base address is specified in <host> element for each service. E.g. <configuration>
<system.servicemodel>
<Services>
<service name=”MyService>
<host>
<baseAddresses>
<add baseAddress =”http://localhost:6070/MyService”>
</baseAddresses>
</host>
</service>
<services>
</system.servicemodel>
</configuration>Thanks Prasham |
SOAP (Simple Object Access Protocol), which is directly supported from WCF (Windows Communication Foundation). |
ABC is the three building blocks of WCF and they are known as A - Address (Where): Address tells us where to find the services, like url B - Bindings (How) : Bindings tells us how to find the services or using which protocols finds the services (SOAP, HTTP, TCT etc.) C - Contacts (What): Contracts are an agreement between the consumer and the service providers that explains what parameters the service expects and what return values it gives. Hope this will be very helpful to understand three building blocks of WCF, a very frequently asked interview questions. |
Hello, The concurrency mode is specified using the ServiceBehavior attribute on the class that implements the service. Ex. [ServiceBehavior(ConcurrencyMode=ConcurrencyMode.Single)] Public class ServiceClass : IServiceInterface{ //Implementation Code } There are 3 possible values of ConcurrencyMode enumeration Single Reentrant Multiple Thanks Prasham |
Hello, WCF supports following 3 types of transactions managers: a. LightWeight b. OLE Transactions c. WS-Atomic Transactions Thanks Prasham |
Hello, Following bindings supports the streaming in WCF: 1. basicHttpBinding 2. netTcpBinding 3. netNamedPipeBinding |
Very useful, thanks keep posting.
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