Setting the start position for OpenFileDialog/Save

问题:

For any custom dialog (form) in a WinForm application I can set its size and position before I display it with:

form.StartPosition = FormStartPosition.Manual;
form.DesktopBounds = MyWindowPosition;

This is particularly important when dealing with multiple monitors. Without such code, when you open a dialog from an application that you have dragged to a second monitor, the dialog appears on the primary monitor. This presents a poor user experience.

I am wondering if there are any hooks to set the position for the standard .NET OpenFileDialog and SaveFileDialog (which do not have a StartPosition property).

回答1:

I suspect that the best you can do is make sure you use the overload of ShowDialog that accepts an IWin32Window to use as the parent. This might help it choose an appropriate location; most commonly:

using(var dlg = new OpenFileDialog()) {
    .... setup
    if(dlg.ShowDialog(this) == DialogResult.OK) {
        .... use
    }
}

回答2:

Check out this article on CodeProject. Excerpt:

Here is when the handy .NET NativeWindow comes into the picture, a NativeWindow is a window wrapper where it processes the messages sent by the handle associated to it. It creates a NativeWindow and associates the OpenFileWindow handle to it. From this point, every message sent to OpenFileWindow will be redirected to our own WndProc method in the NativeWindow instead, and we can cancel, modify, or let them pass through.

In our WndProc, we process the message WM_WINDOWPOSCHANGING. If the open dialog is opening, then we will change the original horizontal or vertical size depending of the StartLocation set by the user. It will increment the size of the window to be created. This happens only once when the control is opened.

Also, we will process the message WM_SHOWWINDOW. Here, all controls inside the original OpenFileDialog are created, and we are going to append our control to the open file dialog. This is done by calling a Win32 API SetParent. This API lets you change the parent window. Then, basically what it does is attach our control to the original OpenFileDialog in the location it set, depending on the value of the StartLocation property.

The advantage of it is that we still have complete control over the controls attached to the OpenFileDialog window. This means we can receive events, call methods, and do whatever we want with those controls.

回答3:

I had this problem for most of yesterday. BobB's answer was the one that helped me out the most (Thanks BobB).

You can even go as far as to make a private method that creates a window and closes it before the dialog.ShowDialog() method call and it will still centre the OpenFileDialog.

private void openFileDialogWindow()
{
    Window openFileDialogWindow = new Window();
    openFileDialogWindow.Left = this.Left;
    openFileDialogWindow.Top = this.Top;
    openFileDialogWindow.Width = 0;
    openFileDialogWindow.Height = 0;
    openFileDialogWindow.WindowStyle = WindowStyle.None;
    openFileDialogWindow.ResizeMode = ResizeMode.NoResize;
    openFileDialogWindow.WindowStartupLocation = WindowStartupLocation.CenterScreen;

    openFileDialogWindow.Show();
    openFileDialogWindow.Close();

    openFileDialogWindow = null;
}

Then call it in any method before the ShowDialog() method.

public string SelectWebFolder()
{
    string WebFoldersDestPath = null;

    CommonOpenFileDialog filePickerDialog = new CommonOpenFileDialog();
    // OpenFileDialog Parameters..

    openFileDialogWindow();

    if (filePickerDialog.ShowDialog() == CommonFileDialogResult.Ok)
    {
        WebFoldersDestPath = filePickerDialog.FileName + "\\";
    }

    filePickerDialog = null;

    return WebFoldersDestPath;
}

回答4:

OpenFileDialog and SaveFileDialog position themselves in the upper-left corner of the client area of the most recently displayed window. So just create a new invisible window positioned where you want the the dialog to appear before creating and showing that dialog.

Window dialogPositioningWindow = new Window();
dialogPositioningWindow.Left = MainWindow.Left + <left position within main window>;
dialogPositioningWindow.Top  = MainWindow.Top  + <top  position within main window>;
dialogPositioningWindow.Width = 0; 
dialogPositioningWindow.Height = 0; 
dialogPositioningWindow.WindowStyle = WindowStyle.None;
dialogPositioningWindow.ResizeMode = ResizeMode.NoResize;
dialogPositioningWindow.Show();// OpenFileDialog is positioned in the upper-left corner
                               // of the last shown window (dialogPositioningWindow)
Microsoft.Win32.OpenFileDialog dialog = new Microsoft.Win32.OpenFileDialog();
...
if ((bool)dialog.ShowDialog()){
   ...
}
dialogPositioningWindow.Close();

回答5:

There is quite an old example of one approach on MSDN.

http://msdn.microsoft.com/en-us/library/ms996463.aspx

It includes all the code needed to implement your own OpenFileDialog class that allows extensibility.

回答6:

Very grateful for BobB's reply on this one. There are a few more "gotchas". You have to pass the handle of PositionForm when calling OpenFileDialog1.ShowDialog(PositionForm) otherwise BobB's technique is not reliable in all cases. Also, now that W8.1 launches a new fileopen control with SkyDrive in it, the Documents folder location in the W8.1 fileopen control is now screwed. So I frig fileopen to use the old W7 control by setting ShowHelp = True.

Here is the VB.NET code I ended up using, my contribution to the community in case it helps.

Private Function Get_FileName() As String

    ' Gets an Input File Name from the user, works with multi-monitors

    Dim OpenFileDialog1 As New OpenFileDialog
    Dim PositionForm As New Form
    Dim MyInputFile As String

    ' The FileDialog() opens in the last Form that was created.  It's buggy!  To ensure it appears in the
    ' area of the current Form, we create a new hidden PositionForm and then delete it afterwards.

    PositionForm.StartPosition = FormStartPosition.Manual
    PositionForm.Left = Me.Left + CInt(Me.Width / 2)
    PositionForm.Top = Me.Top + CInt(Me.Height / 2)
    PositionForm.Width = 0
    PositionForm.Height = 0
    PositionForm.FormBorderStyle = Forms.FormBorderStyle.None
    PositionForm.Visible = False
    PositionForm.Show()

    ' Added the statement "ShowHelp = True" to workaround a problem on W8.1 machines with SkyDrive installed.
    ' It causes the "old" W7 control to be used that does not point to SkyDrive in error.

    OpenFileDialog1.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
    OpenFileDialog1.Filter = "Excel files (*.xls*)|*.xls*|CSV Files (*.csv)|*.csv"
    OpenFileDialog1.FilterIndex = 1
    OpenFileDialog1.RestoreDirectory = True
    OpenFileDialog1.AutoUpgradeEnabled = False
    OpenFileDialog1.ShowHelp = True
    OpenFileDialog1.FileName = ""
    OpenFileDialog1.SupportMultiDottedExtensions = False
    OpenFileDialog1.Title = "Select an Excel or .csv file containing patent data or list of Publication Numbers for your project."

    If OpenFileDialog1.ShowDialog(PositionForm) <> System.Windows.Forms.DialogResult.OK Then
        Console.WriteLine("No file was selected. Please try again!")
        PositionForm.Close()
        PositionForm.Dispose()
        OpenFileDialog1.Dispose()
        Return ""
    End If
    PositionForm.Close()
    PositionForm.Dispose()

    MyInputFile = OpenFileDialog1.FileName
    OpenFileDialog1.Dispose()
    Return MyInputFile

End Function

回答7:

Here's how I did it:

The point where I want to display the OpenFileDialog:

Thread posThread = new Thread(positionOpenDialog);
posThread.Start();

DialogResult dr = ofd.ShowDialog();

The repositioning code:

[DllImport("user32.dll", EntryPoint = "FindWindow", SetLastError = true)]
static extern IntPtr FindWindowByCaption(IntPtr ZeroOnly, string lpWindowName);

[DllImport("user32.dll", EntryPoint = "SetWindowPos")]
public static extern IntPtr SetWindowPos(IntPtr hWnd, int hWndInsertAfter, int x, int Y, int cx, int cy, int wFlags);


/// <summary>
/// Find the OpenFileDialog window when it appears, and position it so
/// that we can see both dialogs at once.  There is no easier way to
/// do this (&^%$! Microsoft!).
/// </summary>
private void positionOpenDialog ()
{
    int count = 0;
    IntPtr zero = (IntPtr)0;
    const int SWP_NOSIZE = 0x0001;
    IntPtr wind;

    while ((wind = FindWindowByCaption(zero, "Open")) == (IntPtr)0)
        if (++count > 100)
            return;             // Find window failed.
        else
            Thread.Sleep(5);

    SetWindowPos(wind, 0, Right, Top, 0, 0, SWP_NOSIZE);
}

I start a thread that looks for a window with the "Open" title. (Typically found in 3 iterations or 15 milliseconds.) Then I set its position with the obtained handle. (See SetWindowPos documentation for the position/size parameters.)

Kludgy.