Custom Controls that use Generics

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Jared - 15 Mar 2007 19:20 GMT

I have created a custom control that uses a generic class to determine what
type of objects will be managed in the control.

The declaration is:
class MyCustomControl<T>:Combobox{
// class stuff
}

The control works great, but I can not use it in the designer. I was
wondering if anyone has had a similar problem and knows if there is a
solution.

Thanks.

Jared

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Bob Powell [MVP] - 15 Mar 2007 20:30 GMT

This is a known issue.
Effectively you can't use an instance of a thing until it can be
instantiated and it can't be instantiated until you pass it the template
parameter...

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> I have created a custom control that uses a generic class to determine
> what type of objects will be managed in the control.
[quoted text clipped - 11 lines]
>
> Jared

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Jared - 15 Mar 2007 21:04 GMT

Thanks. That leads to a second question. I have a similar problem if I
derive a class from the generic class that defines the type.

Using the original example:

class mysecondclass:myclass<someclass>{
}

Gives me an error stating that it cannot create myclass, even though the
template was passed.

I'm guessing it is related to the original issue, but I'm just curious why?

thanks.

> This is a known issue.
> Effectively you can't use an instance of a thing until it can be
[quoted text clipped - 16 lines]
>>
>> Jared

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Oliver Sturm - 16 Mar 2007 20:16 GMT

Hello Jared,

>class mysecondclass:myclass<someclass>{
>}
>
>Gives me an error stating that it cannot create myclass, even though the
>template was passed.

Are you sure? When I have this:

    public class MyGenericPanel<T>: Panel {
        public MyGenericPanel( ) {
        }
    }

    public class MySpecificPanel: MyGenericPanel<string> {
        public MySpecificPanel( ) {
        }
    }

I can drop a MySpecificPanel instance on a form in VS designer without a
problem.

Oliver Sturm

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http://www.sturmnet.org/blog

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Custom Controls that use Generics

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