Microsoft KB Archive/814738

Knowledge Base

BUG: The window style flags that you set when you inherit from the CreateParams property are not applied to the control after you call the Control.SetTopLevel method

Article ID: 814738

Article Last Modified on 11/14/2007

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APPLIES TO

• Microsoft Visual Basic .NET 2003 Standard Edition
• Microsoft Visual Basic .NET 2002 Standard Edition
• Microsoft Visual C# .NET 2003 Standard Edition
• Microsoft Visual C# .NET 2002 Standard Edition
• Microsoft Visual Basic 2005

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SYMPTOMS

The window style flags that you set when you inherit from the CreateParams property are not applied to the control after you call the Control.SetTopLevel method if you follow these steps:

1. You inherit from the System.Windows.Forms.Control class to create a control.
2. You override the CreateParams property.

RESOLUTION

To resolve this bug, reapply the styles to the custom control. To do this, add the following statement after you call the SetTopLevel method:

Visual Basic .NET or Visual Basic 2005 Code

' Reapplies the assigned styles to the control.
myCustomControl.UpdateStyles()

Visual C# .NET Code

// Reapplies the assigned styles to the control.
myCustomControl.UpdateStyles();

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed in the "Applies to" section.

MORE INFORMATION

Steps to Reproduce the Behavior

1. In Microsoft Visual Studio .NET or in Microsoft Visual Studio 2005, start a new class library by using Microsoft Visual Basic .NET, Microsoft Visual Basic 2005, or Microsoft Visual C# .NET.
   
   By default, Class1 is created.

2. In Class1, replace the existing code with the following code:
   
   Visual Basic .NET Code

   Option Explicit On 
   Option Strict On
   Imports System
   Imports System.ComponentModel
   Imports System.Drawing
   Imports System.Collections
   Imports System.Windows.Forms
   
   Public Class MyControl
      Inherits System.Windows.Forms.Control
      Public label1 As System.Windows.Forms.Label
      Public Sub New()
   
         MyBase.New()
         InitializeComponent()
         'Add a label to the control.
         label1 = New System.Windows.Forms.Label()
         label1.Size = New Size(200, 200)
         Me.Controls.Add(label1)
   
      End Sub
      'Dispose any unused resources.
      Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
         If disposing Then
            If Not (components Is Nothing) Then
               components.Dispose()
            End If
         End If
         MyBase.Dispose(disposing)
      End Sub
   
      Private components As System.ComponentModel.IContainer
      <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
   
         components = New System.ComponentModel.Container()
         Me.Size = New System.Drawing.Size(300, 300)
   
      End Sub
   
      Public Const WS_CAPTION As Integer = &HC00000
      Public Const WS_DLGFRAME As Integer = &H400000
      'Override the CreateParams property to assign styles to the control.
      Protected Overrides ReadOnly Property CreateParams() As CreateParams
         Get
            Dim cp As CreateParams
            cp = MyBase.CreateParams
            cp.Style = cp.Style And (Not WS_CAPTION)
            cp.Style = cp.Style Or WS_DLGFRAME
            Return cp
         End Get
      End Property
   
      Shared Sub main()
         'Create a control and set the visible property to true.
         Dim myCustomControl As New MyControl()
         myCustomControl.Visible = True
         'Set the control as the top-level control.
         myCustomControl.SetTopLevel(True)
         myCustomControl.UpdateStyles()
         myCustomControl.label1.Text = "EXPECTED: Border not shown." & vbCrLf & "Alt+F4 to close"
         myCustomControl.Location = New Point(0, 0)
         Application.Run(New ApplicationContext())
      End Sub
   
   End Class
   

   Visual C# .NET Code

   using System;
   using System.Drawing;
   using System.Collections;
   using System.ComponentModel;
   using System.Windows.Forms;
   using System.Data;
   public class MyControl : System.Windows.Forms.Control
   {           
      private System.ComponentModel.Container components = null;
      public System.Windows.Forms.Label label1;
      public MyControl()
      {            
         InitializeComponent();    
         //Add the label to the control.
         label1 = new System.Windows.Forms.Label();
         label1.Size = new Size(200,200);
         this.Controls.Add(label1);
      }
      // Clean up any resources that are being used.   
      protected override void Dispose( bool disposing )
      {
         if( disposing )
         {
            if (components != null) 
            {
               components.Dispose();
            }
         }
         base.Dispose( disposing );
      }
           
      private void InitializeComponent()
      {
         this.components = new System.ComponentModel.Container();
         this.Size = new System.Drawing.Size(300,300);
      }
      private static int WS_DLGFRAME = 0x00400000;
      private static int WS_CAPTION= 0x00c00000;
      //Override the CreateParams property to assign styles to the control.
      protected override CreateParams CreateParams 
      {
         get 
         {
            CreateParams cp = base.CreateParams;
            cp.Style &= ~WS_CAPTION; 
            cp.Style |= WS_DLGFRAME;
            return cp;
         }
      }
      [STAThread]
      static void Main() 
      {    
         //Create a control and set the Visible property to true.
         MyControl myCustomControl = new MyControl();
         myCustomControl.Visible = true;   
         //Set the control as the top-level control. 
         myCustomControl.SetTopLevel(true);
            myCustomControl.UpdateStyles();
         myCustomControl.label1.Text = "EXPECTED: Border not shown.\r\nAlt+F4 to close";
         myCustomControl.Location = new Point(0,0);                
         Application.Run(new ApplicationContext());
      }
   }

3. In Solution Explorer, right-click ClassLibrary1, and then click Add Reference.
4. Click the .NET tab, click to select System.Drawing.dll and System.Windows.Forms.dll, and then click Select.
5. In Solution Explorer, right-click ClassLibrary1, and then click Properties.
6. In Output type, click to select Windows Application.
7. In Startup object, click to select Control1.
8. On the Debug menu, click Start.
   
   The control is displayed with the title bar.

9. Add the following code after you call the SetTopLevel method:
   
   Visual Basic .NET or Visual Basic 2005 Code

   ' Reapplies the assigned styles to the control.
   myCustomControl.UpdateStyles()

   Visual C# .NET Code

   // Reapplies the assigned styles to the control.
   myCustomControl.UpdateStyles();

10. On the Debug menu, click Start to run the application.
    
    The control is displayed without a title bar.

REFERENCES

For more information, visit the following MSDN Web site:

Control.CreateParams Property
http://msdn2.microsoft.com/en-us/library/system.windows.forms.control.createparams(vs.71).aspx

Keywords: kbvs2005swept kbvs2005applies kbvs2002sp1sweep kbstyle kbproperties kbctrl kbcontrol kbbug KB814738

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