[wpf] How to use a FolderBrowserDialog from a WPF application

If you specify Owner, you will get a Modal dialog over the specified WPF window.

To get WinForms compatible Win32 window create a class implements IWin32Window like this

 public class OldWindow : System.Windows.Forms.IWin32Window
{
    IntPtr _handle;

    public OldWindow(IntPtr handle)
    {
        _handle = handle;
    }

    #region IWin32Window Members

    IntPtr System.Windows.Forms.IWin32Window.Handle
    {
        get { return _handle; }
    }

    #endregion
}

And use an instance of this class at your WinForms

        IntPtr mainWindowPtr = new WindowInteropHelper(this).Handle; // 'this' means WPF Window
        folderBrowserDialog.ShowDialog(new OldWindow(mainWindowPtr));