private void button1_Click(object sender, EventArgs e)
        {
string cnn_char = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\MyDB.mdf;Integrated Security=True;User Instance=True";
using (SqlConnection conn = new SqlConnection(cnn_char))
            {
                conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "Select * from T_User where UserName=@User";
                    cmd.Parameters.Add(new SqlParameter("User",textUserName.Text));
using(SqlDataReader reader=cmd.ExecuteReader())
                    {
if (reader.Read())
                        {
int errorTimes = reader.GetInt32(reader.GetOrdinal("ErrorTimes"));


                        }


                    }

                }

            }

        }

private void button3_Click(object sender, EventArgs e)
        {
string cnn_char = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\MyDB.mdf;Integrated Security=True;User Instance=True";
using (SqlConnection conn = new SqlConnection(cnn_char))
             {
                 conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
                 {
                     cmd.CommandText = "Select * from T_User";
                     DataSet dataset = new DataSet();
                     SqlDataAdapter adapter = new SqlDataAdapter(cmd);//将SqlCommand与SqlDataAdapter绑定
                     adapter.Fill(dataset);
                     DataTable table = dataset.Tables[0];
foreach(DataRow row in table.Rows)
                     {
string name=Convert.ToString(row["UserName"]);
                         MessageBox.Show(name);

                     }              
                 }
             }
        }