Standalone WPF Form in VSTO Excel Addin Won't Keep Focus

Question

I am creating a VSTO Plugin for Excel and my first attempt works, but I am not happy with the design. As standard VSTO only handles Windows Forms. I am getting in to WPF now and have found the options for layout and animations make for a much better user experience.

I have now found that I can add a WPF Project to the VSTO Solution and call the forms that way... Excellent!

The problem is when I load a form I do this:

Dim NewForm as New NewForm
NewForm.Show()

This works fine, and the form opens, however if I try to type in a textbox, the form drops behind excel and the text goes in to the active cell in Excel.

If I do:

Dim NewForm as New NewForm
NewForm.ShowDialog()

it works fine. Unfortunately I cannot have the form being modal for my application. How can I get around this?

Answer 1

I use the following class: https://dl.dropboxusercontent.com/u/62538279/Help/OfficeDialog.cs

You'll notice that the ShowDialog() method is replaced

The class also makes the dialog look like a Word VBA form (something my clients often want)

My dialog.xaml.cs class looks like (and the xaml matches):

public partial class myDialog : OfficeDialog

-- Edit --

Here's the source code. I've been having trouble with it. It occasionally slips behind the application (very rarely)

http://stackoverflow.com/questions/40374059/why-does-my-modal-wpf-dialog-slip-behind-ms-word/40401198#40401198

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;

public class OfficeDialog : Window
{

    [DllImport("user32.dll")]
    static extern int GetWindowLong(IntPtr hwnd, int index);
    [DllImport("user32.dll")]
    static extern int SetWindowLong(IntPtr hwnd, int index, int newStyle);
    [DllImport("user32.dll")]
    static extern bool SetWindowPos(IntPtr hwnd, IntPtr hwndInsertAfter, int x, int y, int width, int height, uint flags);
    [DllImport("user32.dll")]
    static extern IntPtr SendMessage(IntPtr hwnd, uint msg, IntPtr wParam, IntPtr lParam);

    const int GWL_EXSTYLE = -20;
    const int WS_EX_DLGMODALFRAME = 0x0001;
    const int SWP_NOSIZE = 0x0001;
    const int SWP_NOMOVE = 0x0002;
    const int SWP_NOZORDER = 0x0004;
    const int SWP_FRAMECHANGED = 0x0020;
    const uint WM_SETICON = 0x0080;
    const int ICON_SMALL = 0;
    const int ICON_BIG = 1;

    /// <summary>
    /// Sometimes get System.ComponentModel.Win32Exception: Invalid window handle
    /// I'm pretty sure that this is because Word is shit at handling windows and has an internal memory leak
    /// http://stackoverflow.com/questions/222649/winforms-issue-error-creating-window-handle
    /// I'm not sure why this error isn't trapped and logged by the try catch below. Somehow it bubbles up to the calling routine..
    /// </summary>
    public OfficeDialog()
    {
        this.ShowInTaskbar = false;
        //this.Topmost = true;

        //Uri uri = new Uri("PresentationFramework.Aero;V3.0.0.0;31bf3856ad364e35;component\\themes/aero.normalcolor.xaml", UriKind.Relative);
        //Uri uri = new Uri("PresentationFramework.Classic;V3.0.0.0;31bf3856ad364e35;component\\themes/classic.xaml", UriKind.Relative);
        //Resources.MergedDictionaries.Add(Application.LoadComponent(uri) as ResourceDictionary);

        //var helper = new WindowInteropHelper(this);
        //using (Process currentProcess = Process.GetCurrentProcess())
        //    helper.Owner = currentProcess.MainWindowHandle;
    }

    public new void ShowDialog()
    {
        try
        {
            var helper = new WindowInteropHelper(this);
            using (Process currentProcess = Process.GetCurrentProcess())
                helper.Owner = currentProcess.MainWindowHandle;
            base.ShowDialog();
        }
        catch (System.ComponentModel.Win32Exception ex)
        {
            Message.LogWarning(ex);
            //this.Topmost = true;
            var helper = new WindowInteropHelper(this);
            using (Process currentProcess = Process.GetCurrentProcess())
                helper.Owner = currentProcess.MainWindowHandle;
            base.ShowDialog();
        }
    }

    protected override void OnSourceInitialized(EventArgs e)
    {
        base.OnSourceInitialized(e);
        RemoveIcon(this);
        HideMinimizeAndMaximizeButtons(this);
        //using (Process currentProcess = Process.GetCurrentProcess())
        //    SetCentering(this, currentProcess.MainWindowHandle);
    }

    public static void HideMinimizeAndMaximizeButtons(Window window)
    {
        const int GWL_STYLE = -16;

        IntPtr hwnd = new WindowInteropHelper(window).Handle;
        long value = GetWindowLong(hwnd, GWL_STYLE);

        SetWindowLong(hwnd, GWL_STYLE, (int)(value & -131073 & -65537));
    }

    public static void RemoveIcon(Window w)
    {
        // Get this window's handle 
        IntPtr hwnd = new WindowInteropHelper(w).Handle;

        // Change the extended window style to not show a window icon
        int extendedStyle = OfficeDialog.GetWindowLong(hwnd, GWL_EXSTYLE);
        OfficeDialog.SetWindowLong(hwnd, GWL_EXSTYLE, extendedStyle | WS_EX_DLGMODALFRAME);

        // reset the icon, both calls important
        OfficeDialog.SendMessage(hwnd, WM_SETICON, (IntPtr)ICON_SMALL, IntPtr.Zero);
        OfficeDialog.SendMessage(hwnd, WM_SETICON, (IntPtr)ICON_BIG, IntPtr.Zero);

        // Update the window's non-client area to reflect the changes
        OfficeDialog.SetWindowPos(hwnd, IntPtr.Zero, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);
    }

    static void SetCentering(Window win, IntPtr ownerHandle)
    {
        bool isWindow = IsWindow(ownerHandle);
        if (!isWindow) //Don't try and centre the window if the ownerHandle is invalid.  To resolve issue with invalid window handle error
        {
            //Message.LogInfo(string.Format("ownerHandle IsWindow: {0}", isWindow));
            return;
        }
        //Show in center of owner if win form.
        if (ownerHandle.ToInt32() != 0)
        {
            var helper = new WindowInteropHelper(win);
            helper.Owner = ownerHandle;
            win.WindowStartupLocation = WindowStartupLocation.CenterOwner;
        }
        else
            win.WindowStartupLocation = WindowStartupLocation.CenterOwner;
    }

    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool IsWindow(IntPtr hWnd);

}