C# 中怎么在显示标题栏的时候，禁止鼠标拖动窗体呢？我是自学菜鸟，望高手不吝赐教。。。

public partial class Form1 : Form
{
const int WM_NCLBUTTONDOWN = 0x00A1;
const int HTCAPTION = 2;

public Form1()
{
InitializeComponent();
}

protected override void WndProc(ref Message m)
{
if (m.Msg == WM_NCLBUTTONDOWN && m.WParam.ToInt32() == HTCAPTION)
return;

base.WndProc(ref m);
}
}