cast of arrays with a given type

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am72de@yahoo.de - 12 Mar 2008 17:21 GMT

Hi all,

I have to write an editor for Visual Studio. It's one editor for
different kind of Arrays: Button[], TextBox[] and so on.
The intern array is Control[], so I can use it for all of the
inherited controls.

But now I don't know how to convert a Control[] back to the given
type.

Please see the following example:

    Button[] btns = new Button[30];
    Control[] ctls = (Control[])btns;

The obvious way to cast the ctls back would be:

    Button[] btns2 = (Button[])ctls;

Does anybody know how to convert it back with only a given type?

Something like that:    Button[] btns3 = ctls as typeof(Button[]);

Thanks in advance
Andy

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Martin Bonner - 12 Mar 2008 17:38 GMT

On Mar 12, 4:21 pm, am7...@yahoo.de wrote:

> Hi all,
>
[quoted text clipped - 5 lines]
> But now I don't know how to convert a Control[] back to the given
> type.

Why do you want to? Can you not just convert the element you /
extract/ from the array?

> Please see the following example:
>
[quoted text clipped - 4 lines]
>
> Button[] btns2 = (Button[])ctls;

... so instead of doing that, you would do:

Button b = (Button)(ctls[i]);

> Does anybody know how to convert it back with only a given type?
>
> Something like that: Button[] btns3 = ctls as typeof(Button[]);

I think what you mean, is that you have a function which has an
argument of type System.Type, and you want to use that to correctly
cast something. Basically, I don't think you can, because there is no
way to declare the argument.

You have a number of choices:
1. Just stick to the properties that are common to "Control".

2. If the range of types is small, do a huge great switch, and handle
each one seperately (you might be able to make the body of the switch
be a function call, and generate the different functions via
generics).

3. Do /everything/ via reflection (get properties, set properties,
call methods). (That is going to be hard work).

4. Generate the code at runtime, and compile it into a subsiduary
assembly.

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am72de@yahoo.de - 12 Mar 2008 20:40 GMT

> On Mar 12, 4:21 pm, am7...@yahoo.de wrote:
>
[quoted text clipped - 46 lines]
> 4. Generate the code at runtime, and compile it into a subsiduary
> assembly.

Unfortunately the editor should handle as many Controls, Buttons and
even Interfaces as possible. All works fine, except the automatic back
cast via a type.
Because the UITypeEditor.EditValue gives me only the
Propertydescriptor - and I don't want to cast every single type - I
thought there has to be a better and simpler way.

Reply to this Message

Ben Voigt [C++ MVP] - 12 Mar 2008 22:25 GMT

> Unfortunately the editor should handle as many Controls, Buttons and
> even Interfaces as possible. All works fine, except the automatic back
> cast via a type.
> Because the UITypeEditor.EditValue gives me only the
> Propertydescriptor - and I don't want to cast every single type - I
> thought there has to be a better and simpler way.

You need to use the PropertyDescriptor.SetValue and friends, there shouldn't
be any casting of the control type required (the component parameter is type
System::Object).

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cast of arrays with a given type

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