C# Winform 文本框默认提示信息

private string Notes = "提示文本";
private void textBox1_Leave(object sender, EventArgs e)
{
// 退出失去焦点，若文本框内容为空，重新显示
if (string.IsNullOrEmpty(textBox1.Text))
{
textBox1.ForeColor = Color.DarkGray;
this.textBox1.Text = Notes;
}
}

private void textBox1_Enter(object sender, EventArgs e)
{
// 进入获得焦点，若文本框内容为“提示文本”，清空
if (textBox1.Text == Notes)
{
textBox1.ForeColor = Color.Black;
this.textBox1.Text = "";
}
}

来源：https://www.cnblogs.com/baissy/p/11724042.html