private void textBox2_TextChanged(object sender, EventArgs e)
  {
   this.textBox2.PasswordChar = '*';
  }

private void button1_Click(object sender, EventArgs e) //登錄按鈕點(diǎn)擊事件
  {
   //獲取文本框中的值
   string userid = this.textBox1.Text;
   string password = this.textBox2.Text;
   if (userid.Equals("") || password.Equals(""))//用戶名或密碼為空
   {
    MessageBox.Show("用戶名或密碼不能為空");
   }
   else//用戶名或密碼不為空
   {
    string connectionString = "Data Source=SC-201609191651;Initial Catalog=BigWork;Persist Security Info=True;User ID=sa;Password=qwe1314521";
    SqlConnection SqlCon = new SqlConnection(connectionString); //數(shù)據(jù)庫(kù)連接
    SqlCon.Open(); //打開數(shù)據(jù)庫(kù)
    string sql = "Select * from users where userid='" + userid + "' and userpwd='" + password + "'";//查找用戶sql語(yǔ)句
    SqlCommand cmd = new SqlCommand(sql,SqlCon);
    cmd.CommandType = CommandType.Text;
    SqlDataReader sdr;
    sdr = cmd.ExecuteReader();
    if (sdr.Read())   //從結(jié)果中找到
    {
     MessageBox.Show("登錄成功", "提示");
    }
    else
    {
     MessageBox.Show("用戶名或密碼錯(cuò)誤", "提示");
     return;
    }
   }
   panel1.Visible = false;
  }

String constr=”data source=.;intial catalog=student;user id=sa;password=”; 
//連接數(shù)據(jù)庫(kù)服務(wù)器
SqlConnection conn=new SqlConnection(constr);           
//SQL連接類的實(shí)例化
Conn.open();                       
//打開數(shù)據(jù)庫(kù)
Messagebox.show(“連接成功！”);                
//彈出窗口，用于測(cè)試數(shù)據(jù)庫(kù)連接是否成功。
String sql=“select * from student”;               
//執(zhí)行的查詢語(yǔ)句
SqlDataAdapeter find=new SqlDataAdapter(sql,conn); 
// 創(chuàng)建DataAdapter數(shù)據(jù)適配器實(shí)例，SqlDataAdapter作用是 DataSet和 SQL Server之間的橋接器，用于檢索和保存數(shù)據(jù)
DataSet save=new DataSet();         
//創(chuàng)建DataSet實(shí)例
find.Fill(save,"wu");            
// 使用DataAdapter的Fill方法(填充)，調(diào)用SELECT命令  fill(對(duì)象名，"自定義虛擬表名") 
DataGridView1.Datasource=save.Tables[0];   
// 向DataGridView1中填充數(shù)據(jù)
conn.close();              
//關(guān)閉數(shù)據(jù)庫(kù)