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();
  }