private void butStyle_Click(object sender, EventArgs e)
    {
      string str = "Data source=.;Initial catalog=Myschool;uid=sa";
      SqlConnection con = new SqlConnection(str);
      string sql = "select count(1) from student where studentName='" + txtUserName.Text + "' and LoginPwd='" + txtPwd.Text + "'";
      SqlCommand cmd = new SqlCommand(sql, con);
      try
      {
        con.Open();
        int count = Convert.ToInt32(cmd.ExecuteScalar());
        if (count > 0)
        {
         MessageBox.Show("登陆成功");
          this.Hide();
          FormMain frm = new FormMain();
          frm.Show();
        }
      }
      catch (Exception)
      {

        MessageBox.Show("退出");
      }
      finally
      {
        con.Close();
      }

private void 新增学生ToolStripMenuItem_Click(object sender, EventArgs e)
    {
      FormStudent formStudent = new FormStudent();
      formStudent.Show();
    }

 public void Save()
    {
      //添加学生
      string pwd = txtpwd.Text;
      string stuname = textname.Text;
      //性别
      string stugender = string.Empty;
      if (radioman.Checked)
      {
        stugender = "1";
      }
      else
      {
        stugender = "0";
      }
      //下拉框绑定数据
      int gid = GeadIdName();
      //联系电话
      string StuPhone = textphone.Text;
      //地址
      string StuAddress = textAddress.Text;
      //日期
      DateTime dt = dateBirthday.Value;
      //邮箱
      string StuEmail = textEmail.Text;
      //LoginPwd, StudentName, Gender, GradeId, Phone, Address, Birthday, Email
      string sql = "insert into Student values('" + pwd + "','" + stuname + "','" + stugender + "'," + gid + ",'" + StuPhone + "','" + StuAddress + "','" + dt + "','" + StuEmail + "')";
      string str = "Data source=.;Initial catalog=Myschool;uid=sa;";
      SqlConnection con = new SqlConnection(str);
      SqlCommand cmd = new SqlCommand(sql, con);
      con.Open();
      int count = cmd.ExecuteNonQuery();
      if (count > 0)
      {
        MessageBox.Show("添加成功");         
      }
      con.Close();
    }

    public void LodaDataListView(string sql)
    {
      string str = "data source=.;initial catalog=Myschool;uid=sa;";
      SqlConnection con = new SqlConnection(str);
      SqlCommand cmd = new SqlCommand(sql, con);
      try
      {
        con.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr != null)
        {
          if (dr.HasRows)
          {
            while (dr.Read())
            {
              int stuNo = Convert.ToInt32(dr["studentNo"]);
              //姓名
              string stuname = Convert.ToString(dr["studentName"]);
              //性别
              string stuGender = Convert.ToString(dr["Gender"]);
              //年级名次
              string stuGname = Convert.ToString(dr["Gradename"]);
              ListViewItem LvItem = new ListViewItem(stuNo.ToString());
              LvItem.SubItems.Add(stuname);
              LvItem.SubItems.Add(stuGender);
              LvItem.SubItems.Add(stuGname);
              //让lvItem和ListView关联
              lvlist.Items.Add(LvItem);
            }
            dr.Close();
          }
        }
      }
      catch (Exception)
      {

        throw;
      }
      finally
      {
        con.Close();
      }
//窗体Load的事件中调用

private void Formselect_Load(object sender, EventArgs e)
    {
      string sql = "select StudentNO,StudentName,Gender,GradeName from Student,Grade where Student.GradeId=Grade.GradeId";
      LodaDataListView(sql);
    }

public void upatae()
    {
      //添加学生
      string pwd = txtpwd.Text;
      string stuname = textname.Text;
      //性别
      string stugender = string.Empty;
      if (radioman.Checked)
      {
        stugender = "1";
      }
      else
      {
        stugender = "0";
      }
      //下拉框绑定数据
      int gid = GeadIdName();
      //联系电话
      string StuPhone = textphone.Text;
      //地址
      string StuAddress = textAddress.Text;
      //日期
      DateTime dt = dateBirthday.Value;
      //邮箱
      string StuEmail = textEmail.Text;
      //LoginPwd, StudentName, Gender, GradeId, Phone, Address, Birthday, Email
      string sql = @"update Student set StudentName='" + stuname + "',Gender=" + stugender + ",GradeId='" + gid + "',phone='" + StuPhone + "',Address='" + StuAddress + "',Birthday='" + dt + "',Email='" + StuEmail
        + "' where studentNo='" + textNo.Text + "'";
      string str = "Data source=.;Initial catalog=Myschool;uid=sa;";
      SqlConnection con = new SqlConnection(str);
      SqlCommand cmd = new SqlCommand(sql, con);
      con.Open();
      int count = cmd.ExecuteNonQuery();
      if (count > 0)
      {
        frmselect.selectData();
        MessageBox.Show("修改成功");
      }
      con.Close();
    }