If you declaring the abstract method then you should not give body
protected abstract bool Validate();
If it is not abstract method declaration but you giving implementation of an abstract method then you should return bool
using return
statement from method method to satisfy the return type in declartion.
protected abstract bool Validate()
{
//The method code
return false;
}
An abstract method declaration introduces a new virtual method but does not provide an implementation of that method. Instead, non-abstract derived classes are required to provide their own implementation by overriding that method. Because an abstract method provides no actual implementation, the method-body of an abstract method simply consists of a semicolon, MSDN.