Can we use abstract class instead of interface in wcf as servicecontract?

I don't know for sure but judging by this MSDN link (http://msdn.microsoft.com/en-us/library/ms734686.aspx) my guess is that you can only use an interface. If it were possible to use an abstract class instead (which has different semantics), then I think the link would have said so.

Try compiling the following.

interface InterfaceBase
{
void Implemented()    // error: interface members cannot have a definition
{
Console.WriteLine();
}
void Unimplemented();
}

abstract class classAbstract
{
void Implemented()
{
Console.WriteLine();
}
abstract public void Unimplemented();
}

You can't compile it; you will get an error. I am sorry that I do not know much about WCF and servicecontracts but I assume that a servicecontract cannot have a class with a method that is implemeted. I hope someone will correct me if I am wrong.