C# Winform 文本框默認提示信息

private string Notes = "提示文本";
private void textBox1_Leave(object sender, EventArgs e)
{
    //  退出失去焦點，重新顯示
    if (string.IsNullOrEmpty(textBox1.Text))
    {
        textBox1.ForeColor = Color.DarkGray;
        this.textBox1.Text = Notes;
    }
}

private void textBox1_Enter(object sender, EventArgs e)
{
    //  進入獲得焦點，清空
    if (textBox1.Text == Notes)
    {
        textBox1.ForeColor = Color.Black;
        this.textBox1.Text = "";
    }
}