C#: How to use .MDIParent in a thread ?

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C#

COM

WinForms

Hello everyone,

I am in front of an issue about mdi child window launched from an automation interface. In my WinForm application, I have a mainframe, a CManager automation class, and a frm child window which will display a 2d object once the CManager.Create2DWindow is invoked.

I am trying the 2d child window creation from vb6, this works until I come to the .MDIParent property, this blows up the cross-thread exception. To simulate it I have tried the experimentation directly from a thread started in CManager.Start()

I have the following code:

public bool Start()
{
   Thread create2DFromThread = new System.Threading.Thread(new System.Threading.ThreadStart(this.Start2DFrom));
   create2DFromThread.IsBackground = true;
   create2DFromThread.SetApartmentState(ApartmentState.STA);
   create2DFromThread.Start();
}

private void Start2DFrom()
{
    frm2D frm = null;
    frm2D = new frm2D();
  
    frm.MdiParent = m_WindowParent;  // --> Illegal Cross Thread Exception.
    frm.Show();
}

I have also tried with delegate but this does not fix the issue.

Do you have an idea how this could be solved ?

Thank you very much in advance.