数据库查找，修改，删除

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

namespace ConnSqlForm
{
public partial class Form4 : Form
{
private SqlConnection Conn;
private SqlCommand Cmd;
public Form4()
{
InitializeComponent();
Conn = new SqlConnection("server=.;database=snewdata;user=sa;pwd=");
}

public DataTable selectStudent()
{
DataTable dt = new DataTable();
Cmd = Conn.CreateCommand();
//查询那个表
Cmd.CommandText = "select *From student";
Conn.Open();
SqlDataReader dr = Cmd.ExecuteReader();
for (int i = 0; i < dr.FieldCount; i++)
{
dt.Columns.Add(dr.GetName(i));
}

while (dr.Read())
{
DataRow row = dt.NewRow();
row["xuehao"] = dr["xuehao"];
row["name"] = dr["name"];
row["sex"] = dr["sex"];
row["birthday"] = dr["birthday"];
dt.Rows.Add(row);
}
Conn.Close();
return dt;
}

private void button1_Click(object sender, EventArgs e)
{
DataTable dt = selectStudent();
listView1.Columns.Clear();
listView1.Columns.Add("学号");
listView1.Columns.Add("姓名");
listView1.Columns.Add("性别");
listView1.Columns.Add("生日");
listView1.Items.Clear();
foreach (DataRow row in dt.Rows)
{
ListViewItem lt = new ListViewItem();
lt.Text = row["xuehao"].ToString();
lt.SubItems.Add(row["name"].ToString());
lt.SubItems.Add(row["sex"].ToString());
lt.SubItems.Add(row["birthday"].ToString());
listView1.Items.Add(lt);
}
}

private void listView1_SelectedIndexChanged(object sender, EventArgs e)
{//选中的索引改变的时候触发selectedindexchanged当选中时触发

}

private void listView1_DoubleClick(object sender, EventArgs e)
{
if (listView1.SelectedItems.Count > 0)
{
string xuehao = listView1.SelectedItems[0].SubItems[0].Text;
string name = listView1.SelectedItems[0].SubItems[1].Text;
string sex = listView1.SelectedItems[0].SubItems[2].Text;
string birthday = listView1.SelectedItems[0].SubItems[3].Text;
Form2 f2 = new Form2(xuehao, name, sex, birthday);
f2.Show();
}
else
{
MessageBox.Show("请选择后双击进行修改");
}
}

private void button2_Click(object sender, EventArgs e)
{
if (listView1.SelectedItems.Count > 0)
{
string xuehao = listView1.SelectedItems[0].SubItems[0].Text;
string name = listView1.SelectedItems[0].SubItems[1].Text;
string sex = listView1.SelectedItems[0].SubItems[2].Text;
string birthday = listView1.SelectedItems[0].SubItems[3].Text;
Form2 f2 = new Form2(xuehao,name,sex,birthday);
f2.Show();
}
else
{
MessageBox.Show("请先选择再点击修改");
}
}

private void button3_Click(object sender, EventArgs e)
{
if (listView1.SelectedItems.Count > 0)
{
SqlCommand cmd = Conn.CreateCommand();
cmd.CommandText = "delete from student where xuehao=@xuehao";
cmd.Parameters.Clear();

cmd.Parameters.Add("@xuehao", listView1.SelectedItems[0].Text);
Conn.Open();
int count = cmd.ExecuteNonQuery();
if (count > 0)
{
MessageBox.Show("删除成功，受影响行数为：" + count.ToString());
}
else
{
MessageBox.Show("删除失败！");
}
Conn.Close();
}
}
}
}