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Why is my inherited window forms control deleted

P: n/a
Hello!

I have a very specific question and that is about how to inherit a visual
control for example the control System.Windows.Forms.TextBox without causing
the environment to delete the control when there are some compile errors.
It's the same problem with any visual control that you inherit. The control
is deleted as soon as you use the View Designer when there is compile error.
It's very easy to reproduce my problem. You can do it in this way.
1. Create a class called ExtTextBox like this. In my example here I have
removed the namespace. But if you include namespace make sure you have
access to it.
public class ExtTextBox : System.Windows.Forms.TextBox
{
public ExtTextBox() {}
}
As you can see this class ExtTextBox inherit from the ordinary components
System.Windows.Forms.TextBox in the .NET framework

2. Create a windows form with any name. The default is Form1

3. Use the View Designer and drag the control TextBox into the window form.
My control was called textBox1

4. Because I want the control textBox1 to be an instance of ExtTextBox I
have to edit the InitializeComponent() I don't have any other idea.
Here is an extract from my windows form called Form1.
Only the interesting rows is written. Two rows is important here.
First saying that control textBox1 is of type ExtTextBox.
Second edit the InitializeComponent and say that textBox1 is an instance of
ExtTextBox.
public class Form1 : Form
{
private ExtTextBox textBox1; // First saying that control textBox1 is of
type ExtTextBox.

....
....
....

Private void InitializeComponent()
{
//Second edit the InitializeComponent and say that textBox1 is an instance
of ExtTextBox
this.textBox1= new ExtTextBox();
...
...
...
}
}

5 Compile. Hopefully you don't get any compile errors. When you run the
applikation only the testBox is being displayed. The problem might start
even here. If you get any compile error and you use the View Designer the
control named textBox1 is being deleted.

6 If you don't get any compile error make a change so you get a compile
error and then use the View Designer the control named textBox1 is being
deleted.

7 Now to my question. I can't use controls that being deleted automatically
when I get compile error as soon as I use the View Designer.

8. If I want to use inheritance on visual control how do I do. I just can't
have it as it is now.

9 I just can't use inheritance in the way I do now.

10. I hope that you have a good suggestion how I should use inheritance on
visual control to avoid this kind of problems.
Additional information: Most of the times there is a project containing
several forms and some code class files. One file in the project is a code
class file which contains this ExtTextBox in this way.
public class ExtTextBox : System.Windows.Forms.TextBox
{
public ExtTextBox() {}
}

When you build the project(assemby) and you get some compile error and you
then use the View Designer on a form containing this inherited control the
control will be deleted.

I have also noted that you can avoid that the control is being deleted but
it's a very annoying way to do it on.
Before you build the project(assembly) you click on Windows->Close All
documents.
Then you build and you get some compile error and you can still use the View
Designer and see the control.
I just can't use that solution having to close all the documents every time
before I build the project.

When I use inheritance I want to extend for example the TextBox class by
additional functionality.
If I create a userControl(see below) for example like this. I can't extent
the class TextBox with additional functionality because the control is a
member in the UserControl class. I can extend the functionality of class
UserControl1 but that is not what I want.
public class UserControl1 : System.Windows.Forms.UserControl
{
private System.Windows.Forms.TextBox textBox1;
...
...
...
private void InitializeComponent()
{
this.textBox1 = new System.Windows.Forms.TextBox():
...
...
...
}
}
I hope that my problem is kind of bug in the .NET framework.
I use VS 2003.

//Tony



Mar 15 '06 #1
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