Question

In some existing piece of code i see the following:

public abstract class BasicComponent<T> : IBasicComponent<T> 
                                          where T : class, new()

I know what an abstract class is, and an interface. But what is it doing with where T and what happends when you extends class and new()?

Answer 1

These are generic type constraints.

The class means that the T you use must be a class (including interface, delegate and arrays), the new that it must have a public parameterless constructor.

From the linked MSDN document:

where T : class –
The type argument must be a reference type; this applies also to any class, interface, delegate, or array type.

where T : new() – The type argument must have a public parameterless constructor. When used together with other constraints, the new() constraint must be specified last.