C# Error CS0689 – Cannot derive from ‘{0}’ because it is a type parameter

C# Error

CS0689 – Cannot derive from ‘{0}’ because it is a type parameter

Reason for the Error & Solution

Cannot derive from ‘identifier’ because it is a type parameter

Base classes or interfaces for generic classes cannot be specified by a type parameter. Derive from a specific class or interface, or a specific generic class instead, or include the unknown type as a member.

The following sample generates CS0689:

// CS0689.cs  
class A<T> : T   // CS0689  
{  
}