c#仿照qq登录界面编辑框内容操作

 using System;
 using System.Drawing;
 using System.Windows.Forms;

 namespace 案例演示
 {
 public partial class frmlogo : Form
 {
 public frmlogo()
 {
 InitializeComponent();
 }
 int usi,pwi;
 private void frmlogo_Load(object sender, EventArgs e)
 {

 }

 private void textBox1_MouseDown(object sender, MouseEventArgs e)
 {
 usi++;
 if (usi==)
 {
 textBox1.Text = "";
 }
 if (textBox2.Text=="")
 {
 pwi = ;
 textBox2.Text = "密码";
 }

 }

 private void textBox2_MouseDown(object sender, MouseEventArgs e)
 {
 pwi++;
 if (textBox1.Text=="")
 {
 textBox1.Text = "用户名";
 usi = ;
 }
 if (pwi==)
 {
 textBox2.Text = "";
 }
 }

 private void textBox1_KeyDown(object sender, KeyEventArgs e)
 {
 textBox1.ForeColor = Color.Black;
 }

 private void textBox2_KeyDown(object sender, KeyEventArgs e)
 {
 textBox2.ForeColor = Color.Black;
 }

 private void button1_Click(object sender, EventArgs e)
 {

 }
 }
 }

 --