C# Linq的简单使用

1.student是数据库中的一张表，学号(stu)和姓名(xingming)是表中的两个字段，学号是主键。

在页面的Page_Load事件中通过Linq查询表中的数据：

    protected void Page_Load(object sender, EventArgs e)

    {

        StudentDataClassesDataContext context = new StudentDataClassesDataContext();

        Table<student> list = context.GetTable<student>();

        var query = from student in list select student;

        foreach (var student in query)

        {

            Response.Write(student.xuehao+","+student.xingming+"<br>");

        }

    }

 

在页面中通过Linq在数据库中添加数据：

    protected void btn_Add_Click(object sender, EventArgs e)

    {

        student stu = new student();

        stu.xuehao = txt_XueHao.Text;

        stu.xingming = txt_XingMing.Text;

        StudentDataClassesDataContext context = new StudentDataClassesDataContext();

        context.student.InsertOnSubmit(stu);

        context.SubmitChanges();

        //重新刷新数据

        Table<student> list = context.GetTable<student>();

        var query = from student in list select student;

        foreach (var student in query)

        {

            Response.Write(student.xuehao + "," + student.xingming + "<br>");

        }

    }

 

通过Linq修改数据：

    protected void btn_Modify_Click(object sender, EventArgs e)

    {

        StudentDataClassesDataContext context = new StudentDataClassesDataContext();

        var query = from student in context.student where student.xuehao == "001" select student;

        foreach (var student in query)

        {

            student.xingming = "宋学习";

        }

        context.SubmitChanges();

    }

 

通过Linq删除数据：

    protected void btn_Delete_Click(object sender, EventArgs e)

    {

        StudentDataClassesDataContext context = new StudentDataClassesDataContext();

        var query=from studen
4000
t in context.student where student.xuehao=="001" select student;

        foreach (var student in query)

        {

            context.student.DeleteOnSubmit(student);

        }

        context.SubmitChanges();

    }