Generics in c# & accessing the static members of T

Asked 2008-08-21T13:20:05.710

My question concerns c# and how to access Static members ... Well I don't really know how to explain it (which kind of is bad for a question isn't it?) I will just give you some sample code:

Class test<T>{
     int method1(Obj Parameter1){
         //in here I want to do something which I would explain as
         T.TryParse(Parameter1);

         //my problem is that it does not work ... I get an error.
         //just to explain: if I declare test<int> (with type Integer)
         //I want my sample code to call int.TryParse(). If it were String
         //it should have been String.TryParse()
     }
}

So thank you guys for your answers (By the way the question is: how would I solve this problem without getting an error). This probably quite an easy question for you!

Edit: Thank you all for your answers!

Though I think the try - catch phrase is the most elegant, I know from my experience with vb that it can really be a bummer. I used it once and it took about 30 minutes to run a program, which later on only took 2 minutes to compute just because I avoided try - catch.

This is why I chose the switch statement as the best answer. It makes the code more complicated but on the other hand I imagine it to be relatively fast and relatively easy to read. (Though I still think there should be a more elegant way ... maybe in the next language I learn)

Though if you have some other suggestion I am still waiting (and willing to participate)

Edit Report

3 Answers

The problem is that TryParse isn't defined on an interface or base class anywhere, so you can't make an assumption that the type passed into your class will have that function. Unless you can contrain T in some way, you'll run into this a lot.

Constraints on Type Parameters

answered 2008-08-21T13:28:29.513

To access a member of a specific class or interface you need to use the Where keyword and specify the interface or base class that has the method.

In the above instance TryParse does not come from an interface or base class, so what you are trying to do above is not possible. Best just use Convert.ChangeType and a try/catch statement.

class test<T>
{
    T Method(object P)
    {
       try {
           return (T)Convert.ChangeType(P, typeof(T));
       } catch(Exception e) {
           return null;
       }
    }
}

answered 2008-08-21T13:34:47.923

You may want to read my previous post on limiting generic types to primitives. This may give you some pointers in limiting the type that can be passed to the generic (since TypeParse is obviously only available to a set number of primitives ( string.TryParse obviously being the exception, which doesn't make sense).

Once you have more of a handle on the type, you can then work on trying to parse it. You may need a bit of an ugly switch in there (to call the correct TryParse ) but I think you can achieve the desired functionality.

If you need me to explain any of the above further, then please ask :)

answered 2008-08-21T13:35:06.003

Generics in c# & accessing the static members of T

3 Answers

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