Visually remove/disable close button from title bar .NET

Question

I have been asked to remove or disable the close button from our VB .NET 2005 MDI application. There are no native properties on a form that allow you to grey out the close

Answer 1

Based on the latest information you added to your question, skip to the end of my answer.

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This is what you need to set to false: Form.ControlBox Property

BUT, you will lose the minimize and maximize buttons as well as the application menu (top left).

As an alternative, override OnClose and set Cancel to true (C# example):

protected override void OnFormClosing(FormClosingEventArgs e)
{
    if (e.CloseReason != CloseReason.WindowsShutDown && e.CloseReason != CloseReason.ApplicationExitCall)
    {
        e.Cancel = true;
    }

    base.OnFormClosing(e);
}

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If neither of these solutions are acceptable, and you must disable just the close button, you can go the pinvoke/createparams route:

How to disable close button from window form using .NET application

This is the VB version of jdm's code:

Private Const CP_NOCLOSE_BUTTON As Integer = &H200
Protected Overloads Overrides ReadOnly Property CreateParams() As    CreateParams
   Get 
      Dim myCp As CreateParams = MyBase.CreateParams 
      myCp.ClassStyle = myCp.ClassStyle Or CP_NOCLOSE_BUTTON 
      Return myCp 
   End Get 
End Property