声明一个事件：

 Num_DiscountAmount.MouseWheel +=new MouseEventHandler(Num_DiscountAmount_MouseWheel);

编写一个事件

private void  Num_DiscountAmount_MouseWheel(object sender, MouseEventArgs e)
{
HandledMouseEventArgs h = e as HandledMouseEventArgs;
if (h != null)
{
h.Handled = true;
}
}

还有 第三方控件　DevExpress.XtraEditors.SpinEdit ,如何禁用鼠标中间键　？

方法如下：

声明事件： (SpinEdit1.Controls[0] as DevExpress.XtraEditors.TextBoxMaskBox).MouseWheel += new MouseEventHandler(Frm_MouseWheel);

编写事件：

void Frm_MouseWheel(object sender, MouseEventArgs e)
{
if (e.Delta != 0)
DevExpress.Utils.DXMouseEventArgs.GetMouseArgs(e).Handled = true;
}