Q: What is Contracts in WCF ?
ServiceContracts
OperationContracts
DataContracts

Q: What is endpoint in WCF?
It describes the actual behavior or operation of the service at runtime

Q: What is duplex contracts in WCF?
WCF Services can communicate with client through a callback - is called duplex messaging pattern. Duplex messaging in WCF can be done over different transports, like TCP, Named Pipes and even HTTP

Q: What are the various ways of hosting a WCF service?

1. Self hosting: - The service code is embedded within the application code. An end point for the service is defined and an instance of SeriveHost is created. A method can be written then to call the service.

2. Managed Windows services: - here, some hosting code is written in the application code. It consists of registering the application domain as a windows service.

3. Internet Information Services: - Does not require any hosting code to be written in the application code. IIS host services can only use HTTP transport mechanism. IIS needs to be installed and configured on the server.

4. Windows process activation service:- Does not require any hosting code to be written in the application code. WAS needs to be installed and configured on the server. WCF uses the listener adapter interface to communicate activation requests. Requests are transported over non HTTP protocols.

Q: What are 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.

Q: What is REST in WCF?
Read here

Q: What is InstanceContextMode in WCF?
This property value indicate when new service objects are created ? the property has three value
the default is PerSession

1. PerCall:

2. PerSession:

3. Single:

Q: What is ConcurrencyMode in WCF?
This property value indicate how service supports thread? the property has three value
the default is PerSession

1. Single:

2. Multiple :

3. Reentrant :

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