c# - 访问 WinCE ComboBox DroppedDown 属性 (.NET CF 2.0)

Question

我正在实现对表单控件进行子类化的自定义行为，但我无法设法访问 ComboBox 的 DroppedDown 属性。看帮助，CF.NET 2.0应该支持:

 using System;

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

 namespace xCustomControls
 {
     public partial class xComboBox : System.Windows.Forms.ComboBox
     {
         private ComboBox comboBox1;

         public xComboBox()
         {
             InitializeComponent();
             this.KeyDown += new KeyEventHandler(this.KeyDownHandler);
         }

         private void KeyDownHandler(object sender, KeyEventArgs e)
         {
                // DroppedDown doesn't appear in the IntelliSense of ComboBox.
                // or this.comboBox1.
             if (((ComboBox)sender).DroppedDown)     // fail!
                 return;

             switch (e.KeyData)
             {
                 case Keys.Up:
                 case Keys.Enter:
                 case Keys.Down:
                     e.Handled = true;
                     this.Parent.SelectNextControl((Control)sender, e.KeyData != Keys.Up, true, true, true);

...

失败，“System.Windows.Forms.ComboBox”不包含“DroppedDown”的定义，并且找不到接受“System.Windows.Forms.ComboBox”类型的第一个参数的扩展方法“DroppedDown”

如何访问该属性？

TIA,巴勃罗

Answer 1

DroppedDown 属性不在 compact-framework 中，但您可以使用这样的东西:

public const int CB_GETDROPPEDSTATE = 0x0157;
public static bool GetDroppedDown(ComboBox comboBox)
{
 Message comboBoxDroppedMsg = Message.Create(comboBox.Handle, CB_GETDROPPEDSTATE, IntPtr.Zero, IntPtr.Zero);

 MessageWindow.SendMessage(ref comboBoxDroppedMsg);

 return comboBoxDroppedMsg.Result != IntPtr.Zero;
}

取自:http://msdn.microsoft.com/en-us/netframework/bb735847.aspx