C# generic parameters

Question

Let's say I have some generic interface IMyInterface<TParameter1, TParameter2>.

Now, if I'm writing another class, generic on it's parameter T:

CustomClass<T> where T : IMyInterface

how should this be done?

(current code won't compile, because IMyInterface is dependent on TParameter, TParameter2).

I assume it should be done like:

CustomClass<T, TParameter1, TParameter2> where T: IMyInterface<TParameter1,
                                                               TParameter2>

but I might be wrong, could you advice me please?

Darin Dimitrov · Accepted Answer · 2011-02-02 20:58:05Z

4

It's exactly as you have it, you need to specify the TParameter1 and TParameter2 generic arguments in a class which requires a generic constraint on IMyInterface:

public interface IMyInterface<TParameter1, TParameter2>
{ 
}

public class CustomClass<T, TParameter1, TParameter2> 
    where T : IMyInterface<TParameter1, TParameter2>
{

}

or you could have them fixed:

public class CustomClass<T> 
    where T : IMyInterface<string, int>
{

}

answered Feb 2, 2011 at 20:58

Darin Dimitrov

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Comments

Jay · Accepted Answer · 2011-02-02 21:07:01Z

0

Do you really want to use it as a constraint (with the 'where' keyword)? Here are some examples of straight implementation:

interface ITwoTypes<T1, T2>

class TwoTypes<T1, T2> : ITwoTypes<T1, T2>

Or, if you know the type(s) your class will use, you don't need a type parameter on the class:

class StringAndIntClass : ITwoTypes<int, string>

class StringAndSomething<T> : ITwoTypes<string, T>

If you are using the interface as a constraint and don't know the types to specify explicitly, then yes, you need to add the type parameters to the class declaration, as you supposed.

class SomethingAndSomethingElse<T, TSomething, TSomethingElse> where T : ITwoTypes<TSomething, TSomethingElse>

class StringAndSomething<T, TSomething> where T : ITwoTypes<string, TSomething>

edited Feb 2, 2011 at 21:07

answered Feb 2, 2011 at 21:01

Jay

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