Showing a hint for a C# winforms edit control

Question

I'm working on a C# winforms application (VS.NET 2008, .NET 3.5 sp 1). I have a search field on a form, and rather than have a label next to the search field I'd like to show some grey text in the background of the search field itself ('Search terms', for example). When the user starts entering text in the search field the text should disappear. How can I achieve this?

Answer 1

You will need to use some P/Inovke interop code to do this. Look for the Win32 API SendMessage function and the EM_SETCUEBANNER message.

Answer 2

Its better to post the code instead of link. I am posting this from here

            //Copyright (c) 2008 Jason Kemp

            //Permission is hereby granted, free of charge, to any person obtaining a copy
            //of this software and associated documentation files (the "Software"), to deal
            //in the Software without restriction, including without limitation the rights
            //to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
            //copies of the Software, and to permit persons to whom the Software is
            //furnished to do so, subject to the following conditions:

            //The above copyright notice and this permission notice shall be included in
            //all copies or substantial portions of the Software.

            //THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
            //IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
            //FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
            //AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
            //LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
            //OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
            //THE SOFTWARE.

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


            public static class Win32Utility
            {
                [DllImport("user32.dll", CharSet = CharSet.Auto)]
                private static extern Int32 SendMessage(IntPtr hWnd, int msg,
                    int wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);

                [DllImport("user32.dll")]
                private static extern bool SendMessage(IntPtr hwnd, int msg, int wParam, StringBuilder lParam);

                [DllImport("user32.dll")]
                private static extern bool GetComboBoxInfo(IntPtr hwnd, ref COMBOBOXINFO pcbi);

                [StructLayout(LayoutKind.Sequential)]
                private struct COMBOBOXINFO
                {
                    public int cbSize;
                    public RECT rcItem;
                    public RECT rcButton;
                    public IntPtr stateButton;
                    public IntPtr hwndCombo;
                    public IntPtr hwndItem;
                    public IntPtr hwndList;
                }

                [StructLayout(LayoutKind.Sequential)]
                private struct RECT
                {
                    public int left;
                    public int top;
                    public int right;
                    public int bottom;
                }

                private const int EM_SETCUEBANNER = 0x1501;
                private const int EM_GETCUEBANNER = 0x1502;

                public static void SetCueText(Control control, string text)
                {
                    if (control is ComboBox)
                    {
                        COMBOBOXINFO info = GetComboBoxInfo(control);
                        SendMessage(info.hwndItem, EM_SETCUEBANNER, 0, text);
                    }
                    else
                    {
                        SendMessage(control.Handle, EM_SETCUEBANNER, 0, text);
                    }
                }

                private static COMBOBOXINFO GetComboBoxInfo(Control control)
                {
                    COMBOBOXINFO info = new COMBOBOXINFO();
                    //a combobox is made up of three controls, a button, a list and textbox;
                    //we want the textbox
                    info.cbSize = Marshal.SizeOf(info);
                    GetComboBoxInfo(control.Handle, ref info);
                    return info;
                }

                public static string GetCueText(Control control)
                {
                    StringBuilder builder = new StringBuilder();
                    if (control is ComboBox)
                    {
                        COMBOBOXINFO info = new COMBOBOXINFO();
                        //a combobox is made up of two controls, a list and textbox;
                        //we want the textbox
                        info.cbSize = Marshal.SizeOf(info);
                        GetComboBoxInfo(control.Handle, ref info);
                        SendMessage(info.hwndItem, EM_GETCUEBANNER, 0, builder);
                    }
                    else
                    {
                        SendMessage(control.Handle, EM_GETCUEBANNER, 0, builder);
                    }
                    return builder.ToString();
                }
            }