combo box dropdown position

Question

dear friends

I have a maximum size form which has the combobox (docked in top-right) and the combobox width is set to 500 px.

now , the dropdown appear out of the screen , I want to set he dropdown position to start from right side to left side;

// I use the visual studio 2008 and C# language //
// thank you ashish yadav

thank you . -mironline

Answer 1

you have not mentioned which language is being used. but this link should help http://old.nabble.com/-flex_india:7607--ComboBox-dropdown-position---td15832061.html

Answer 2

Tricky problem. I could not find a good fix for this, merely a workaround. Add a new class and paste the code shown below. Compile. Drop the new control from the top of the toolbox onto your form.

The workaround is not a very good one. The problem is that the dropdown window will ignore the attempt to move it until the drop-down animation is complete. The visual effect is not great, you'll see the window drop down, then jump to the left. I don't know an other way to slap it over the head, maybe somebody else does.

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;

public class MyComboBox : ComboBox {
  protected override void OnDropDown(EventArgs e) {
    // Is dropdown off the right side of the screen?
    Point pos = this.PointToScreen(this.Location);
    Screen scr = Screen.FromPoint(pos);
    if (scr.WorkingArea.Right < pos.X + this.DropDownWidth) {
       this.BeginInvoke(new Action(() => {
        // Retrieve handle to dropdown list
        COMBOBOXINFO info = new COMBOBOXINFO();
        info.cbSize = Marshal.SizeOf(info);
        SendMessageCb(this.Handle, 0x164, IntPtr.Zero, out info);
        // Move the dropdown window
        RECT rc;
        GetWindowRect(info.hwndList, out rc);
        int x = scr.WorkingArea.Right - (rc.Right - rc.Left);
        SetWindowPos(info.hwndList, IntPtr.Zero, x, rc.Top, 0, 0, 5);
      }));
    }
    base.OnDropDown(e);
  }

  // P/Invoke declarations
  private struct COMBOBOXINFO {
    public Int32 cbSize;
    public RECT rcItem, rcButton;
    public int buttonState;
    public IntPtr hwndCombo, hwndEdit, hwndList;
  }
  private struct RECT {
    public int Left, Top, Right, Bottom;
  }
  [DllImport("user32.dll", EntryPoint = "SendMessageW", CharSet = CharSet.Unicode)]
  private static extern IntPtr SendMessageCb(IntPtr hWnd, int msg, IntPtr wp, out COMBOBOXINFO lp);
  [DllImport("user32.dll")]
  private static extern bool SetWindowPos(IntPtr hWnd, IntPtr after, int x, int y, int cx, int cy, int flags);
  [DllImport("user32.dll")]
  private static extern bool GetWindowRect(IntPtr hWnd, out RECT rc);
}