Question

What exactly are we telling the compiler in this line of code ?

public abstract class RepositoryBase<T> where T:class

Are we saying that when we create an object that inherits from RepositoryBase, the object must take a class in the constructor otherwise there will be a compile error ?

Answer 1

It’s saying that when you inherit from RepositoryBase<T>, the type T which you specify must be some type of class (or interface or etc., but not a value type). For example RepositoryBase<int> is illegal and won’t compile: see Constraints on Type Parameters (C# Programming Guide).