在C＃ToolBox中派生两个扩展控件，一个包含另一个

Question

I have two controls inside my Class Library one named TextBox and one Panel, I am able to derive them differently in my ToolBox but what I want is instead of deriving two different controls I want my textbox inside the panel and derive just panel so that it contains both panel and textbox. I am facing an issue while doing it. Panel is easily available in Toolbox but the textbox object I created inside the Panel is not visible. Can anyone tell me is this thing achievable?

public class TextBoxPanel :Panel
{
    TextBoxPanel()
    {
        IpTextBox ip = new IpTextBox();
    }

    protected override void OnPaint(PaintEventArgs e)
    {
    }

    public class IPField : TextBox
    {
        protected override void OnClick(EventArgs e)
        {

        }
    }
}

Answer 1

You can't extend from multiple base classes. Your intuition to derive from your Panel is correct since you want a TextBox inside a Panel .

The big question is WHY do you "need" to derive from TextBox ? If you just need a TextBox inside your new control then simply adding an instance of it to your Panel is enough.

If the TextBox provides additional functionality through an API which you want to expose from the new TextBoxPanel then I suggest something along these lines:

public interface ICoolStuff
{
   public String HelloWorld();
}

public class TextBox : Control, ICoolStuff
{
    // *snip*
}

public class TextBoxPanel : Panel, ICoolStuff
{
    public string HelloWorld()
    {
        return this.textbox.HelloWorld();
    }
}

IF the functionality your textbox provides is not dependent on the textbox itself then it would be even better to separate it into a completely different class