您不能定义这样的约束，但你可以在运行时检查类型。这不会帮助你，虽然做计算。

You can't define such a constraint, but you could check the type at runtime. That won't help you for doing calculations though.

如果你想要做计算，这样的事情将是一种选择：

If you want to do calculations, something like this would be an option:

class Calculations<T, S> where S: Calculator<T>, new()
{
    Calculator<T> _calculator = new S();

    public T Square(T a)
    {
        return _calculator.Multiply(a, a);
    }

}

abstract class Calculator<T>
{
    public abstract T Multiply(T a, T b);
}

class IntCalculator : Calculator<int>
{
    public override int Multiply(int a, int b)
    {
        return a * b;
    }
}

同样的，定义一个 FloatCalculator ，你需要的任何操作。这不是特别快，但比C＃4.0 dynamic$c$c>构建。

Likewise, define a FloatCalculator and any operations you need. It's not particularly fast, though faster than the C# 4.0 dynamic construct.

var calc = new Calculations<int, IntCalculator>();
var result = calc.Square(10);

一个副作用是，你将只能够实例计算器如果你传递给它的类型有一个匹配的计算器＆LT; T＆GT; 执行，这样你就不必做运行时类型检查。

A side-effect is that you will only be able to instantiate Calculator if the type you pass to it has a matching Calculator<T> implementation, so you don't have to do runtime type checking.

这基本上是Hejlsberg为在这次采访那里的问题进行了讨论参照。我个人还是希望看到一些基本类型：）

This is basically what Hejlsberg was referring to in this interview where the issue is discussed. Personally I would still like to see some kind of base type :)