使用linq查询sql server
1.查询数据库首要添加Linq to sql类文件其步骤为
a.创建windows窗体应用程序
b.添加新项 linq to sql 类
c.将数据表映射到DataClasses1.dbml中
直接将数据表拖到DataClasses1.dbml中
d.在窗体内添加 一个dgv,textbox,button,lable
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 LINQ_to_SQL
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
string str = @"server=.\SQLEXPRESS;database=LINQ;uid=;pwd=";
linqtosqlDataContext linq;//声明linq连接对象
public SqlConnection connection()
{
SqlConnection conn = new SqlConnection(str);
return conn;
}//数据库连接方法
private void dgv()
{
SqlConnection con = connection();
con.Open();
SqlDataAdapter sda = new SqlDataAdapter("select * from information",con);
DataSet ds = new DataSet();
sda.Fill(ds);
dataGridView1.DataSource = ds.Tables[0];
con.Close();
}
private void Form1_Load(object sender, EventArgs e)
{
// TODO: 这行代码将数据加载到表“lINQDataSet.information”中。您可以根据需要移动或删除它。
this.informationTableAdapter.Fill(this.lINQDataSet.information);
dgv();
}
private void button1_Click(object sender, EventArgs e)
{
linq = new linqtosqlDataContext(str);
if (textBox1.Text == "")
{//获取所有员工的信息
var result = from info in linq.information
select new
{
编号 = info.ID,
姓名 = info.NAME,
性别 = info.SEX,
年龄 = info.AGE,
电话 = info.TEL
};
dataGridView1.DataSource = result;
}
else
{
switch(comboBox1.Text)
{
case "编号":
var resultid = from info in linq.information
where info.ID.equals(textBox1.text)
select new
{
编号 = info.ID,
姓名 = info.NAME,
性别 = info.SEX,
年龄 = info.AGE,
电话 = info.TEL
};
dataGridView1.DataSource = resultid;
break;
case "姓名":
var resultname = from info in linq.information
where info.NAME.Contains(textBox1.Text)
select new
{
编号 = info.ID,
姓名 = info.NAME,
性别 = info.SEX,
年龄 = info.AGE,
电话 = info.TEL
};
dataGridView1.DataSource = resultname;
break;
case "年龄":
var resultage = from info in linq.information
select new
{
编号 = info.ID,
姓名 = info.NAME,
性别 = info.SEX,
年龄 = info.AGE,
电话 = info.TEL
};
dataGridView1.DataSource = resultage;
break;
}
}
}
}
}