SqlCommand对象修改SQL Server

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace SqlCommand对象修改SQL_Server
{
public partial class Form1 : Form
{
private SqlConnection conn = null;
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
if (conn!=null&&conn.State == ConnectionState.Open) return;
string connectionString = "Data Source=黄武-PC;Initial Catalog=db_14;Integrated Security=True";
string query = "UPDATE Employees SET FirstName=@FirstName WHERE FirstName='Charles'";
conn = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand(query, conn);
try
{
conn.Open();
cmd.Parameters.AddWithValue("@FirstName", "Margarent");
int count1 = cmd.ExecuteNonQuery();
string data = "";
cmd.CommandText = "SELECT COUNT(*) FROM Employees";
int count2 = (int)cmd.ExecuteScalar();
data += "目前一共有" + count2.ToString() + "条记录：\r\n\r\n";
cmd.CommandText = "SELECT LastName+' '+FirstName AS Name,Title FROM Employees";
SqlDataReader reader = cmd.ExecuteReader();
data += "姓名\t\t\t头衔\r\n";
data += "------------------------------"+Environment.NewLine;
while (reader.Read())
{
data += string.Format("{0,-20}\t\t{1}\r\n", reader["Name"], reader["Title"]);
}
data += count1.ToString() + "条记录被更新。\r" + Environment.NewLine;
this.textBox1.Text = data;
reader.Close();
}
catch (SqlException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
conn.Close();
}
}

private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
if (conn != null && conn.State == ConnectionState.Open)
conn.Close();
}
}
}