combobox只读代码

 public partial class Form1: Form
     {
         // combobox只读代码
         [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
         public static extern IntPtr GetWindow(IntPtr hWnd, int uCmd);
         int GW_CHILD = ;
         [DllImport("user32.dll", CharSet = CharSet.Auto)]
         public static extern IntPtr SendMessage(IntPtr hWnd, int msg, int wParam, int lParam);
         public const int EM_SETREADONLY = 0xcf;
         //构造函数
         public Form1()
         {
             InitializeComponent();
             IntPtr editHandle = GetWindow(this.comboBox1.Handle, GW_CHILD);
             SendMessage(editHandle, EM_SETREADONLY,,); //第四个参数"0"代表只读，设置为"1"为可编辑
         }
     }