求教吧友

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 WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void display()
{
string str = "Data Source=xie-PC;Integrated Security=True";
SqlConnection con = new SqlConnection(str);
string sql = "select * from student";
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = sql;
cmd.Connection = con;
SqlDataAdapter sda = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
sda.Fill(ds);
this.dataGridView1.DataSource = ds.Tables[0];
}
private void Form1_Load(object sender, EventArgs e)
{
display();
}
private void button1_Click(object sender, EventArgs e)
{
string str = "Data Source=xie-PC;Integrated Security=True";
SqlConnection con = new SqlConnection(str);
string sql = "select * from student where Age>=" + this.textBox1.Text;
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = sql;
cmd.Connection = con;
SqlDataAdapter sda=new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
sda.Fill(ds);
this.dataGridView1.DataSource = ds.Tables[0];
}
private void button2_Click(object sender, EventArgs e)
{
Form2 f = new Form2();
f.Show();
this.Hide();
}
private void button3_Click(object sender, EventArgs e)
{
string str = "Data Source=xie-PC;Integrated Security=Truee";
SqlConnection con = new SqlConnection(str);
string sql = "delete from student where Name=" + "'" + this.textBox2.Text + "'";
SqlCommand del_cmd = new SqlCommand();
del_cmd.CommandText = sql;
del_cmd.Connection = con;
con.Open();
del_cmd.ExecuteNonQuery();
display();
}
}
}

@什么都没留wj

你为何不单独写个类来调用数据库？，下面是最简单的增删改查，能实现读取数据修改数据之类的
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;
namespace CCC
{
class DBHelper
{
//链接数据库
private static readonly string constring = "Data Source=.;Initial Catalog=phone;Integrated Security=True";
private static SqlConnection con = new SqlConnection(constring);
//打开数据库
private static void Open()
{
if (con.State==ConnectionState.Closed)
{
con.Open();
}
}
//关闭数据库
private static void Close()
{
if (con.State==ConnectionState.Open)
{
con.Close();
}
}
//读取数据库（查询）
public static DataTable GetTable(string sql)
{
Open();
SqlCommand cmd = new SqlCommand(sql, con);
DataTable dt = new DataTable();
SqlDataAdapter apt = new SqlDataAdapter(cmd);
apt.Fill(dt);
return dt;
}
//增删改（int）
public static int ExecuteNonQuery(string sql)
{
int rult = 0;
try
{
Open();
SqlCommand cmd = new SqlCommand(sql, con);
rult = cmd.ExecuteNonQuery();
}
catch (Exception)
{
;
}
finally
{
Close();
}
return rult;
}
}
}