Hi Lance,

Sorry for the late response.

Due to the US holiday and internal bug database update, we got a lot delay
on contacting the Winform team. Now, I can find the bug record to the
Winform team. I am working with them on this issue.

I will get back to you ASAP. Thanks for your patient.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
==================================================
Get notification to my posts through email? Please refer to
http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif
ications.

Note: The MSDN Managed Newsgroup support offering is for non-urgent issues
where an initial response from the community or a Microsoft Support
Engineer within 1 business day is acceptable. Please note that each follow
up response may take approximately 2 business days as the support
professional working with you may need further investigation to reach the
most efficient resolution. The offering is not appropriate for situations
that require urgent, real-time or phone-based interactions or complex
project analysis and dump analysis issues. Issues of this nature are best
handled working with a dedicated Microsoft Support Engineer by contacting
Microsoft Customer Support Services (CSS) at
http://msdn.microsoft.com/subscriptions/support/default.aspx.
==================================================
This posting is provided "AS IS" with no warranties, and confers no rights.

Hi Lance,

During the discussion, the Winform confirmed that there is some painting
logic order wrong in showing the MDI child form. It seems that the
problematic drawing embeded deep in the Layout code. After spending a lot
effect to find a workaround, one Winform developer is able to find a
workaround. The workaround logic is like this:
"Basically, when you create the childform, set its position to (-1000,
-1000) (outside the screen). After it is set to visible, then you put it
back in the correct spot. When you set it to visible=false, then set it
outiside the screen again."
The modified repro sample is listed below, you may give it a try:

Public Class Form1
Inherits Windows.Forms.Form

Protected WithEvents Button1 As Windows.Forms.Button
Protected ChildForms() As Windows.Forms.Form

Public Sub New()
MyBase.New()
Me.IsMdiContainer = True
Me.Size = New Drawing.Size(800, 600)

Const n As Integer = 4
Const uBound As Integer = (n - 1)
Dim childForms(uBound) As Windows.Forms.Form
Dim position As Integer = 0
Const delta As Integer = 24
For i As Integer = 0 To uBound
childForms(i) = New Windows.Forms.Form
childForms(i).MdiParent = Me
childForms(i).FormBorderStyle = Windows.Forms.FormBorderStyle.None
childForms(i).ControlBox = False
childForms(i).StartPosition = FormStartPosition.Manual
childForms(i).Location = New Drawing.Point(position-1000, position-1000)
position += delta
Next i
Me.ChildForms = childForms

Me.Button1 = New Windows.Forms.Button
Me.Button1.Text = "Click Me"

Dim topPanel As New Windows.Forms.Panel
topPanel.Height = Me.Button1.Height
topPanel.Dock = DockStyle.Top
topPanel.Controls.Add(Me.Button1)

Me.Controls.Add(topPanel)
End Sub

Private Sub Button1_Click(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Button1.Click
For i As Integer = 0 To Me.ChildForms.GetUpperBound(0)
Me.ChildForms(i).Visible = (Not Me.ChildForms(i).Visible)
If Me.ChildForms(i).Visible Then
Me.ChildForms(i).Location = New Drawing.Point(Me.ChildForms(i).Location.X +
1000, Me.ChildForms(i).Location.Y + 1000)
Else
Me.ChildForms(i).Location = New Drawing.Point(Me.ChildForms(i).Location.X -
1000, Me.ChildForms(i).Location.Y - 1000)
End If
Next i
End Sub

Protected Overrides Sub OnMdiChildActivate(ByVal e As System.EventArgs)
' The following simulates code that might be executed when an MdiChild is
activated, such as merging menus.
Dim duration As New System.TimeSpan(0, 0, 1)
Dim startTime As System.DateTime = System.DateTime.Now
While ((System.DateTime.Now - startTime) < duration)
End While
MyBase.OnMdiChildActivate(e)
End Sub

End Class

Hope this helps.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
==================================================
Get notification to my posts through email? Please refer to
http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif
ications.

Note: The MSDN Managed Newsgroup support offering is for non-urgent issues
where an initial response from the community or a Microsoft Support
Engineer within 1 business day is acceptable. Please note that each follow
up response may take approximately 2 business days as the support
professional working with you may need further investigation to reach the
most efficient resolution. The offering is not appropriate for situations
that require urgent, real-time or phone-based interactions or complex
project analysis and dump analysis issues. Issues of this nature are best
handled working with a dedicated Microsoft Support Engineer by contacting
Microsoft Customer Support Services (CSS) at
http://msdn.microsoft.com/subscriptions/support/default.aspx.
==================================================
This posting is provided "AS IS" with no warranties, and confers no rights.