LinQ to sql

第一篇       从CUD开始，如何使用LINQ  to SQL插入、修改、删除数据 

准备工作，现在数据库中建好测试表Student，这个表只有三个字段ID,Name,Hometown，其中ID为int类型的自增长字段，Name和Howmtown是nvarchar类型

1. 打开VS2010新建控制台应用程序，然后添加LINQ to SQL Class，命名为DbApp.dbml，新建dbml文件之后，可以打开server explorer，建立数据库连接，并将我们新建的表拖到dbml文件中，结果如下图

 

2． 可以通过点击dbml文件空白处，按F4显示dbml属性，可以修改Context和生成实体的命名空间

 

3． 到现在为止VS2010通过工具为我们创建好了数据表对应实体类和数据表操作添，改，删的方法，现在开始实践

1） 添加 Add

static void Add()

{

    //添加一个Student

    Student aStudent = new Student

    {

        Name = "张小二",

        Hometown = "南海观音院"

    };

    Console.WriteLine("----------begin Add a student");

    using (DbAppDataContext db = new DbAppDataContext())

    {

        db.Log = Console.Out;

        db.Students.InsertOnSubmit(aStudent);

        db.SubmitChanges();

    }

 

    Console.WriteLine("----------End Add a student");

}

输出的sql语句 

INSERT INTO [dbo].[Student]([Name], [Hometown])

VALUES (@p0, @p1)

 

SELECT CONVERT(Int,SCOPE_IDENTITY()) AS [value]

使用linq to sql执行Edit 编辑操作

private static void Edit(int id)

{

    Console.WriteLine("----------begin edit");

    using (DbAppDataContext db = new DbAppDataContext())

    {

        db.Log = Console.Out;

 

    //取出student

    var editStudent = db.Students.SingleOrDefault<Student>(s=>s.ID == id);

 

    if (editStudent == null)

    {

        Console.WriteLine("id错误");

        return;

    }

 

    //修改student的属性

    editStudent.Name = "张小三";

    editStudent.Hometown = "张家口张家寨张家营";

 

    //执行更新操作

    db.SubmitChanges();

 

    }

    Console.WriteLine("---------end edit Student");

}

输出的sql语句

SELECT [t0].[ID], [t0].[Name], [t0].[Hometown]

FROM [dbo].[Student] AS [t0]

WHERE [t0].[ID] = @p0

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [6]

-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 4.0.30319.1

 

UPDATE [dbo].[Student]

SET [Name] = @p3, [Hometown] = @p4

WHERE ([ID] = @p0) AND ([Name] = @p1) AND ([Hometown] = @p2)

3）使用linq to sql 执行删除操作

执行代码：

static void Delete(int id)

{

    Console.WriteLine("-----------begin delete a student");

    using (DbAppDataContext db = new DbAppDataContext())

    {

        db.Log = Console.Out;

        //取出student

        var student = db.Students.SingleOrDefault<Student>(s => s.ID == id);

 

        if (student == null)

        {

            Console.WriteLine("student is null");

            return;

        }

 

        db.Students.DeleteOnSubmit(student);

 

        db.SubmitChanges();

    }

    Console.WriteLine("------------end Delete student");

}

生成的sql语句：

SELECT [t0].[ID], [t0].[Name], [t0].[Hometown]

FROM [dbo].[Student] AS [t0]

WHERE [t0].[ID] = @p0

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [6]

-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 4.0.30319.1

 

DELETE FROM [dbo].[Student] WHERE ([ID] = @p0) AND ([Name] = @p1) AND ([Hometown

] = @p2)

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [6]

-- @p1: Input NVarChar (Size = 4000; Prec = 0; Scale = 0) [张小三]

-- @p2: Input NVarChar (Size = 4000; Prec = 0; Scale = 0) [张家口张家寨张家营]

-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 4.0.30319.1