Constraints on type parameters - where T: class

Question

I have problem with constraints, because I want, that the type argument is a reference type just one of 3 classes, not the any others, so constraint "where L: class" is not ok.

Here is example:

public class MyClass <L> 
        where L : Circle
        where L: Rectangle
        where L: Triangle

This mean, that must comply with all constraints. Unfortunately, I have not found the answer yet.

Thank you very much.

Answer 1

You should create a base class or interface that Circle, Rectangle, and Triangle inherit from.

For example:

interface IShape
{
}

class Circle : IShape
{
    // ...
}

class Rectangle : IShape
{
    // ...
}

class Triangle : IShape
{
    // ...
}

Then do the constraint on IShape:

public class MyClass <L> 
    where L : IShape