c#中不能直接隐藏可编辑控件的光标的功能，真是奇怪！
只能通过WINDOWS API的HideCaret函数来实现
HideCaret函数的申明：
[DllImport("user32", EntryPoint = "HideCaret")]
private static extern bool HideCaret(IntPtr hWnd);
为TextBox添加MouseDown事件：
textbuttons[i].MouseDown += new MouseEventHandler(FrmSend_MouseDown);
void FrmSend_MouseDown(object sender, MouseEventArgs e)
...{
//throw new Exception("The method or operation is not implemented.");
HideCaret(((TextBox)sender).Handle);
}