如何让文本框显示提示信息

QQ上输入账号密码的时候会有一个提示信息，这个是如何实现的呢？

正文

//用户名自动提示private void txtUserID_Enter(object sender, EventArgs e){txtUserID.Focus();txtUserID.Text = "请输入用户名";txtUserID.ForeColor = Color.LightGray;}private void txtUserID_Leave(object sender, EventArgs e){if (txtUserID.Text == ""){txtUserID.Text = "请输入用户名";txtUserID.ForeColor = Color.LightGray;}}//点击用户文本框，内容清空private void txtUserID_MouseClick(object sender, MouseEventArgs e){txtUserID.Text = "";}private void txtPassWord_MouseClick(object sender, MouseEventArgs e){txtPassWord.Text = "";}//密码自动提示private void txtPassWord_Enter(object sender, EventArgs e){txtPassWord.Text = "请输入密码";txtPassWord.ForeColor = Color.LightGray;}//离开自动回复密码提示private void txtPassWord_Leave(object sender, EventArgs e){if (txtPassWord.Text == ""){txtPassWord.Text = "请输入密码";txtPassWord.ForeColor = Color.LightGray;}}//密码框为*private void txtPassWord_TextChanged(object sender, EventArgs e){if (txtPassWord.Text == "" && txtPassWord.Text != "请输入密码"){txtPassWord.PasswordChar = Convert.ToChar("*");}}

小结

这个功能逻辑有点绕，还需要再研究一下。