如何在具有多个约束的C＃中实现泛型方法

Question

I want to write a generic method:

void Foo<T>(IList<T> list)

In the method, I want to compare elements of list either by using operator < if T is primitive type or Compare() if T implements IComparable.

Is this possible? If not, it means C# generics is very limited in use I think.

Answer 1

Is this possible? If not, it means C# generics is very limited in use I think.

Even if it weren't possible, generics can be used in many many situations.

However, it's really simple given that all the primitive types implement IComparable<T> ;

void Foo<T>(IList<T> list) where T : IComparable<T>
{
    T x = ...;
    T y = ...;
    if (x.CompareTo(y) < 0)
    {
        ...
    }
}

Note that this will not introduce boxing operations. I'd expect the JITted code for primitive types to end up having very similar performance to hardcoding it to use < or > .

Now this is a slightly special case, because there's an interface which is roughly equivalent to those operators. What isn't as easy is using arithmetic operators ( + , - etc). See the article on my web site for a few approaches to this.