How do I cast a type to a typename?

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4.00/5 (1 vote)

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Say I have a method with generic parameters, how do I enter:

doSomething<foo.GetType()>();

Why doesn't this work and how can I make this work?

Posted 18-Jan-14 22:29pm

The Kcrownikown

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Kornfeld Eliyahu Peter 19-Jan-14 4:41am

I think you can't do this in a simple way like in your example.
You may need a lot of reflection...
Read here http://msdn.microsoft.com/en-us/library/4xxf1410(v=vs.110).aspx

2 solutions

Solution 1

As I know, foo.GetType() is invoked at runtime, so you should try by using typeof(foo) that is managed at compile time.

Posted 18-Jan-14 22:47pm

Raul Iloc

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OriginalGriff · Accepted Answer · 2014-01-18T22:47:00

Why? Simple: because you have no parameters, the decision as to what type to call your method with is decided at compile time - the type cannot be inferred from the usage. Which mean you have to provide a constant type specifier, rather than a method call.

Instead, try this:

C#

private void DoSomething<T>()
    {
    Console.WriteLine("DoSomething:" + typeof(T));
    }
private void DoSomething<T>(T x)
    {
    Console.WriteLine("DoSomething:" + x.GetType());
    }

Then you can call it:

C#

DoSomething<int>();
DoSomething<float>();
double d = 12.34;
DoSomething(d);

And get what you want:

DoSomething:System.Int32
DoSomething:System.Single
DoSomething:System.Double