Combobox DropDownList默认提示输入文字

Question

所以它基本上与Default text in combobox相同，但是对于一个旧窗体项目。

如何在winforms下拉列表中设置提示文本？

Answer 1

有使用的PInvoke在http://www.aaronlerch.com/blog/2007/12/01/watermarked-edit-controls/

然而笔者注意到，设置“提示”文本的这一个实现...

这将仅适用于Windows XP工作，更高，只有如果视觉 样式启用

...和docs for CB_SETCUEBANNER状态的最小客户端是Windows Vista中。所以它可能不适合所有的环境。

万一页面消失，这里的相关类：

CueComboBox.cs 

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Text; 
using System.Windows.Forms; 
using System.Runtime.InteropServices; 

namespace Lerch.Samples 
{ 
    public class CueComboBox : ComboBox 
    { 
     #region PInvoke Helpers 

     private static uint CB_SETCUEBANNER = 0x1703; 

     [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)] 
     private static extern IntPtr SendMessage(HandleRef hWnd, uint Msg, IntPtr wParam, String lParam); 

     #endregion PInvoke Helpers 

     #region CueText 

     private string _cueText = String.Empty; 

     /// <summary> 
     /// Gets or sets the text the <see cref="ComboBox"/> will display as a cue to the user. 
     /// </summary> 
     [Description("The text value to be displayed as a cue to the user.")] 
     [Category("Appearance")] 
     [DefaultValue("")] 
     [Localizable(true)] 
     public string CueText 
     { 
      get { return _cueText; } 
      set 
      { 
       if (value == null) 
       { 
        value = String.Empty; 
       } 

       if (!_cueText.Equals(value, StringComparison.CurrentCulture)) 
       { 
        _cueText = value; 
        UpdateCue(); 
        OnCueTextChanged(EventArgs.Empty); 
       } 
      } 
     } 

     /// <summary> 
     /// Occurs when the <see cref="CueText"/> property value changes. 
     /// </summary> 
     public event EventHandler CueTextChanged; 

     [EditorBrowsable(EditorBrowsableState.Advanced)] 
     protected virtual void OnCueTextChanged(EventArgs e) 
     { 
      EventHandler handler = CueTextChanged; 
      if (handler != null) 
      { 
       handler(this, e); 
      } 
     } 

     #endregion CueText 

     #region Overrides 

     protected override void OnHandleCreated(EventArgs e) 
     { 
      UpdateCue(); 

      base.OnHandleCreated(e); 
     } 

     #endregion Overrides 

     private void UpdateCue() 
     { 
      // If the handle isn't yet created, 
      // this will be called when it is created 
      if (this.IsHandleCreated) 
      { 
       SendMessage(new HandleRef(this, this.Handle), CB_SETCUEBANNER, IntPtr.Zero, _cueText); 
      } 
     } 
    } 
}