Windows窗体,SendMessage行中的语法错误

我正在使用Windows窗体,并尝试使用SendMessage获取组合框下拉矩形。然而,我似乎找不到允许代码编译的正确参数组合。

以下是一些未编译的行的示例:

var z1 = SendMessage(hWnd, CB_GETDROPPEDCONTROLRECT, (IntPtr)1, (IntPtr)0);  // The best overloaded match has some invalid arguments.

var z2 = SendMessage(hWnd, 0x0152, (IntPtr)1, (IntPtr)0); 

var z3 = SendMessage(hWnd, CB_GETDROPPEDCONTROLRECT, 1, 0); 

var z4 = SendMessage(hWnd, 0x0152, 1, 0);

提前感谢任何有任何想法使这项工作的人。

public partial class Form1 : Form
{
    [DllImport("user32.dll")]
    public static extern int SendMessage(
          int hWnd,      // handle to destination window
          uint Msg,       // message
          long wParam,  // first message parameter
          long lParam   // second message parameter
          );

    public Form1()
    {
        InitializeComponent();
        List<string> itms = new List<string>();
        itms.Add("Choice 1");
        itms.Add("Choice 2");
        itms.Add("Choice 3");
        itms.Add("Choice 4");
        itms.Add("Choice 5");

        this.comboBox1.Items.AddRange(itms.ToArray());
    }

    private void comboBox1_DropDown(object sender, EventArgs e)
    {
        const int CB_GETDROPPEDCONTROLRECT = 0x0152;
        IntPtr hWnd = comboBox1.Handle;

        var z = SendMessage(hWnd, CB_GETDROPPEDCONTROLRECT, (IntPtr)1, (IntPtr)0);  // The best overloaded match has some invalid arguments.

        var z1 = SendMessage(hWnd, 0x0152, (IntPtr)1, (IntPtr)0); 
    }
}