How to center a modeless .Net Form in ArcMap

Question

I am able to setup the owner of the form so that the modeless dialog will minimize with ArcMap and stay ontop of ONLY ArcMap but I am unable to get a modeless dialog to center on ArcMap even when I have its StartupPosition set to CenterParent. I have tried the following:
public override void onCreate(object hook) {
     m_pApplication = hook as IApplication
}

public override void OnClick() {
     IntPtr pIntPtr = new IntPtr(m_pApplication.hWnd);
     MyForm pMyForm = new MyForm();
     pMyForm.Show((System.Windows.Forms.Form)System.Windows.Forms.Form.FromHandle(pIntPrt);
}

Maybe the CenterParent property does not apply to a Modeless Form?

Thanks,
   -eric

RichardColeman · Answer

I've been trying to display a modeless form with the parent ArcMap form as the parent.

This code works, but only the first time.

IntPtr pPtr = new IntPtr(_application.hWnd);
_parentWindow = (System.Windows.Forms.Form)System.Windows.Forms.Form.FromHandle(pPtr);
 this.Show(_parentWindow);

Where _application is a valid reference to the current IApplication ArcMap object

If I close the dialog box and try to open it a second time, _parentWindow is always null.  Even though _application.hWnd > 0.

Is there any reason why this only works once?

How can I create a modeless dialog in ArcMap (C#) that the user can open and close and will always have ArcMap as the parent?

Thanks,

rick.

EricPaitz · Answer

Thanks everyone! Based on all the comments these are the two small classes I came up with. The first is just a way to wrap the IApplication and expose its Handle as a IWin32Window. This class can be used as the owner of the Show() method on a Form. That will deal with being ontop of the ArcMap application (only) and to minimize, maximize and restore with the ArcMap application too. The second class is a base class that any of my modeless forms can inherit from. Thanks again! 🙂
public class IApplicationWrapper : System.Windows.Forms.IWin32Window {
 System.IntPtr m_pIntPtr;

public IApplicationWrapper(IApplication pApplication) {
  m_pIntPtr = new IntPtr(pApplication.hWnd);
 }
 public IApplicationWrapper(SystemIntPtr pIntPtr) {
  m_pIntPtr = pIntPtr;
 }
 IntPtr System.Windows.Forms.IWin32Windwo.Handle {
  Get { return m_pIntPtr; }
 }
}

public class BaseForm : System.Windows.Forms.Form {
 private IApplication m_pApplication = null;

~BaseForm() {
  ESRI.ArcGIS.ADF.ComRelease.ReleaseCOMObject(m_pApplication);
 }

protected override void OnLoad(EventArgs e) {
  if (m_pApplication != null) {
   this.Left = (((((IWindowPosition)m_pApplication).Width / 2) + ((IWindowPosition)m_pApplication).Left) �?? (this.Width / 2));
   this.Top = (((((IWindowPosition)m_pApplication).Height / 2) + ((IWindowPosition)m_pApplication).Top) �?? (this.Height / 2));
  }
  base.OnLoad(e);
 }
 public void Show(IApplication pApplication) {
  m_pApplication = pApplication
  this.Show(new IApplicationWrapper(pApplication));
 }
}

kenbuja · Answer

When I call my modeless form, I initialize its position to the center of the ArcMap window with the following code.

Dim InitializeForm As New myProject.Processing
  InitializeForm.Form_Initialize(m_application)
  InitializeForm.Show(New Win32HWNDWrapper(m_application.hWnd))

the following is the code for the form

Public Class Processing

Friend Sub Form_Initialize(ByVal m_Application As ESRI.ArcGIS.Framework.IApplication)

Dim pWinPos As ESRI.ArcGIS.Framework.IWindowPosition
    Dim CenterX As Short
    Dim CenterY As Short

pWinPos = m_Application
    CenterX = (pWinPos.Width / 2) + pWinPos.Left
    CenterY = (pWinPos.Height / 2) + pWinPos.Top

Me.Left = CenterX - Me.Width / 2
    Me.Top = CenterY - Me.Height / 2

End Sub

End Class

the following is the code for the class Win32HWNDWrapper

Public Class Win32HWNDWrapper
  Implements System.Windows.Forms.IWin32Window
  Private _hwnd As System.IntPtr

Public ReadOnly Property Handle() As System.IntPtr Implements System.Windows.Forms.IWin32Window.Handle
    Get
      Return _hwnd
    End Get
  End Property

Public Sub New(ByVal Handle As System.IntPtr)
    _hwnd = Handle
  End Sub
End Class