generic method to add int, float, in c#

Question

I am writing a generic method for addition of integers, float, double

public T  Swap<T>( T value1,  T value2)
{
    T temp;
    temp = value1 +value2;
    return temp;
}

I am getting an error:

Operator '+' cannot be applied to operands of type 'T' and 'T'

I am using VS 2005, can anyone tell me how to achive it?

It can't be done. There's no way to constrain a generic type to be numeric, which would (hand-wave) be what is necessary to have this work. — Damien_The_Unbeliever
– Damien_The_Unbeliever, Commented Jul 30, 2011 at 15:31
Didn't Mono do something like interfaces for basic arithmetic, with compiler support for the basic types? I wonder how long it'll take for Microsoft to realize it would be a nice addition in their release as well. — Matti Virkkunen
– Matti Virkkunen, Commented Jul 30, 2011 at 15:36

Jon Skeet · Accepted Answer · 2011-07-30 15:49:09Z

6

You can't do this directly. Generics in .NET just don't support it. However, there are other options available:

In C# 4, you can use dynamic typing:
```
public static T Sum<T>(T value1,  T value2)
{
    dynamic temp = value1;
    temp += value2;
    return temp;
}
```
EDIT: I hadn't noticed that you were using VS2005. Do you really have to? Any chance you could upgrade to something a little more recent?
Marc Gravell wrote code in MiscUtil to do this pretty efficiently with delegates. See the usage page for more information. The implementation in MiscUtil uses C# 3 and .NET 3.5, but I believe Marc has a separate implementation of the same ideas in .NET 2 using DynamicMethod. We can ping him to check if you need that...

answered Jul 30, 2011 at 15:34

Jon Skeet

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1 Comment

I didn't think you could do C# 4 in VS2005.