ASP.NET web control only allow specific contents?

I am new to ASP .N开发者_高级运维ET web controls, but not ASP .NET in general or C#.

I am wondering how I can limit the allowed content types to a specific class.

I have made a custom web control called TabPanel, and I want it to only be able to contain TabPages.

As an example, the following markup should be illegal, since it contains a checkbox.

<cc1:TabPanel ID="TabPanel1" runat="server">
    <cc1:TabPage runat="server">
        this is a simple test
    </cc1:TabPage>
    <cc1:TabPage runat="server">
        this is another simple test
    </cc1:TabPage>
    <asp:CheckBox runat="server" />
</cc1:TabPanel>

In this case, I wouldn't want the checkbox to be there. How can I block this from happening?

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I have not tried exactly what you are after but based on other things I have done I would try this:

• Create a property in TabPannel that is a collection of TabPages (call it Tabs for demonstration purposes). This can be an array, a list, or a custom collection class, the key is to have typed to only accept TabPages as members.
• Give the property the [PersistenceMode(PersistenceMode.InnerProperty)] atribute.
• Override CreateChildControls to add the contents of the collection to the control.

If you do it this way then your mark up should end up looking something like this:

<cc1:TabPanel ID="TabPanel1" runat="server">
    <Tabs>
        <cc1:TabPage runat="server">this is a simple test</cc1:TabPage>
        <cc1:TabPage runat="server">this is another simple test</cc1:TabPage>
    </Tabs>
</cc1:TabPanel> 

and it should not allow anything that is not a TabPage to be nested inside of the Tabs property.

http://msdn.microsoft.com/en-us/library/9txe1d4x(v=VS.90).aspx is a walk through demonstrating this technique in detail.

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I figured it out.

Had to throw an exception under AddedControl procedure that I overrided from the WebControl if the type of the control being added was not of the type I wanted.

Now the designer shows a beautiful red error-message on the control itself, preventing me from doing such a foolish thing.

Awesome!

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I'm going to take a guess here, but based on some quick googling I think you're looking for the ControlBuilder. The demo limits their control to an object called "mycell", but I don't see any reason why this couldn't be limited to your own objects, or build-in ASP.NET controls (i.e. Panels but not TextBoxes, etc.)

As a last resort, I'm sure you could hijack the rendering method and only render controls within the pre-determined class set, but this seems hack-ish at best.