数据库操作(c#)

windows窗体程序中的数据库操作部分

//数据库连接串

internal static string connstring = "Data Source = 192.168.1.1; Initial Catalog = testdb; User ID = test; pwd = 111111;";        

//学生登录

using (SqlConnection conn = new SqlConnection(login_mainform.connstring))

                {

                    string sql = "select * from test_student where name=@name and pwd=@pwd";

                    SqlCommand cmd = new SqlCommand(sql, conn);

                    cmd.Parameters.Add(new SqlParameter("@name", txtusername.Text));

                    cmd.Parameters.Add(new SqlParameter("@pwd", txtpassword.Text));

                    conn.Open();

                    SqlDataReader reader = cmd.ExecuteReader();

                    Student stu = new Student();

                    if (reader.Read())

                    {

                        stu.Sno = reader[].ToString();

                        stu.Name = reader[].ToString();

                        stu.Major = reader[].ToString();

                        stu.Birthday = reader[].ToString();

                        stu.Sex = (reader[].ToString())==""?"男":"女";

                        Information info = new Information(stu); //新窗口对象

                        info.Show(); //显示学生信息

                        this.Hide(); //隐藏当前窗口

                    }

                    else

                    {

                        MessageBox.Show("输入有误");

                    }

                    #endregion

                }

//修改数据

                using (SqlConnection conn = new SqlConnection(login_mainform.connstring))

                {

                    string sql = "update test_student set pwd=@pwd where sno=@sno";

                    SqlCommand cmd = new SqlCommand(sql,conn);

                    cmd.Parameters.Add(new SqlParameter("@pwd", txtnewpwd.Text));

                    cmd.Parameters.Add(new SqlParameter("@sno", txtsno.Text));

                    conn.Open();

                    int rows= cmd.ExecuteNonQuery();

                    if (rows>)

                    {

                        MessageBox.Show("密码修改成功,请重新登录");

                        login_mainform form = new login_mainform(); //登录窗口

                        form.Show();

                        this.Close();

                    }

                    else MessageBox.Show("存储出错");

                }

//连接数据库查询符合查询条件的数据 adapter

            using (SqlConnection conn = new SqlConnection(login_mainform.connstring))

            {

                conn.Open();

                String sql =String.Format("select sno,name,sex,birthday,major from test_student where name like '%{0}%' and major like '%{1}%' and sno like '%{2}%'", txtnamequery.Text,cmbmajor.Text,txtsnoquery.Text);

                SqlDataAdapter da = new SqlDataAdapter(sql,conn);

                DataSet ds = new DataSet();

                da.Fill(ds);

                }
                

//更新密码

         using (SqlConnection conn = new SqlConnection(login_mainform.connstring))

                {

                    conn.Open();

                    string sno = dgvstudent.CurrentRow.Cells[].Value.ToString();

                    String sql = String.Format("update test_student set pwd = '123456' where sno = {0}", sno);

                    SqlCommand cmd = new SqlCommand(sql, conn);

                    int rows = cmd.ExecuteNonQuery();

                    if (rows > )

                        MessageBox.Show("重置成功。密码：123456");

                    else return;

                }