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  • Entity Framework 6 Recipes 2nd Edition(10-9)译 -> 在多对多关系中为插入和删除使用存储过程

    10-9. 在多对多关系中为插入和删除使用存储过程

    问题

    想要在一个无载荷的多对多关系中使用存储过程(存储过程只影响关系的连接表)

    解决方案

    假设有一个多对多关系的作者( Author)表和书籍( Book)表. 用连接表AuthorBook来做多对多关系,如 Figure 10-11.所示:

     

    Figure 10-11. A payload-free, many-to-many relationship between an Author and a Book

    当把表生成模型,那么模型就如Figure 10-12所示:

    Figure 10-12. The model created by importing the tables in Figure 10-11

    接下来用存储过程创建插入和删除操作:

    1.在数据库中,创建如Listing 10-23所示的存储过程.

    Listing 10-23. The stored Procedures for the Insert and Delete Actions

    create procedure [chapter10].[InsertAuthorBook]

    (@AuthorId int,@BookId int)

    as

    begin

    insert into chapter10.AuthorBook(AuthorId,BookId) values (@AuthorId,@BookId)

    end

    go

     

    create procedure [chapter10].[DeleteAuthorBook]

    (@AuthorId int,@BookId int)

    as

    begin

    delete chapter10.AuthorBook where AuthorId = @AuthorId and BookId = @BookId

    end

    2. 右击模型设计视图,选择“从数据库中更新模型”,选择 Listing 10-23所创建的存储过程,单击“完成”,这样就把存储过程添加到了模型里。

    3. 目前版本的EF没有为一个关系插入和删除操作映射的设计视图,只能用手工去映射, 右击.edmx 文件,选择“打开方式”,选择“XML (文本)编辑器”. 在<AssociationSetMapping> 标签下插入 Listing 10-24所示的代码(译注:根据自己的例子命名修改代码里的)

    Listing 10-24. Mapping the Stored Procedures to the Insert and Delete Actions for the Many-to-Many Association

                <ModificationFunctionMapping>

                  <InsertFunction FunctionName="EFRecipesModel1009.Store.InsertAuthorBook">

                    <EndProperty Name="Author">

                      <ScalarProperty Name="AuthorId" ParameterName="AuthorId" />

                    </EndProperty>

                    <EndProperty Name="Book">

                      <ScalarProperty Name="BookId" ParameterName="BookId" />

                    </EndProperty>

                  </InsertFunction>

                  <DeleteFunction FunctionName="EFRecipesModel1009.Store.DeleteAuthorBook">

                    <EndProperty Name="Author">

                      <ScalarProperty Name="AuthorId" ParameterName="AuthorId" />

                    </EndProperty>

                    <EndProperty Name="Book">

                      <ScalarProperty Name="BookId" ParameterName="BookId" />

                    </EndProperty>

                  </DeleteFunction>

                </ModificationFunctionMapping>

    接下来Listing 10-25 代码演示了插入和删除操作.你可以用Sql Profiler来查看当

    InsertAuthorBook 和DeleteAuthorBook 存储过程被EF在更新多对多关系时调用后生成的SQL语句

    Listing 10-25. Inserting into the Model

        class Program

        {

            static void Main(string[] args)

            {

                using (var context = new EFRecipesEntities1009())

                {

                    context.Database.ExecuteSqlCommand("delete from chapter10.AuthorBook");

                    context.Database.ExecuteSqlCommand("delete from chapter10.book");

                    context.Database.ExecuteSqlCommand("delete from chapter10.Author");

     

                    var auth1 = new Author { Name = "Jane Austin" };

                    var book1 = new Book

                    {

                        Title = "Pride and Prejudice",

                        ISBN = "1848373104"

                    };

                    var book2 = new Book

                    {

                        Title = "Sense and Sensibility",

                        ISBN = "1440469563"

                    };

                    auth1.Books.Add(book1);

                    auth1.Books.Add(book2);

                    var auth2 = new Author { Name = "Audrey Niffenegger" };

                    var book3 = new Book

                    {

                        Title = "The Time Traveler's Wife",

                        ISBN = "015602943X"

                    };

                    auth2.Books.Add(book3);

                    context.Authors.Add(auth1);

                    context.Authors.Add(auth2);

                    context.SaveChanges();

                    context.Books.Remove(book1);

                    context.SaveChanges();

                }

                Console.WriteLine(" press any key to exit...");

                Console.ReadKey();

     

            }

    }

    SQL Profiler里跟踪到的SQL语句如下(Listing 10-25)所示:

    exec sp_executesql N'insert [Chapter10].[Author]([Name])values (@0)

    select [AuthorId] from [Chapter10].[Author]

    where @@ROWCOUNT > 0 and [AuthorId] = scope_identity()',N'@0 varchar(50)',@0='Jane Austin'

     

    exec sp_executesql N'insert [Chapter10].[Author]([Name])values (@0)

    select [AuthorId] from [Chapter10].[Author]

    where @@ROWCOUNT > 0 and [AuthorId] = scope_identity()',N'@0 varchar(50)',

    @0='Audrey Niffenegger'

     

    exec sp_executesql N'insert [Chapter10].[Book]([Title], [ISBN])values (@0, @1)

    select [BookId]    from [Chapter10].[Book]

    where @@ROWCOUNT > 0 and [BookId] = scope_identity()',N'@0 varchar(50),

    @1 varchar(50)',@0='Pride and Prejudice',@1='1848373104'

     

    exec sp_executesql N'insert [Chapter10].[Book]([Title], [ISBN])values (@0, @1)

    select [BookId] from [Chapter10].[Book]

    where @@ROWCOUNT > 0 and [BookId] = scope_identity()',N'@0 varchar(50),

    @1 varchar(50)',@0='Sense and Sensibility',@1='1440469563'

     

    exec sp_executesql N'insert [Chapter10].[Book]([Title], [ISBN])values (@0, @1)

    select [BookId]  from [Chapter10].[Book]

    where @@ROWCOUNT > 0 and [BookId] = scope_identity()',N'@0 varchar(50),

    @1 varchar(50)',@0='The Time Traveler''s Wife',@1='015602943X'

     

    exec [Chapter10].[InsertAuthorBook] @AuthorId=1,@BookId=1

    exec [Chapter10].[InsertAuthorBook] @AuthorId=1,@BookId=2

    exec [Chapter10].[InsertAuthorBook] @AuthorId=2,@BookId=3

     

    exec [Chapter10].[DeleteAuthorBook] @AuthorId=1,@BookId=1

    exec sp_executesql N'delete [Chapter10].[Book] where ([BookId] = @0)',N'@0 int',@0=1

    它是如何工作的?

    为把存储过程映射到多对多关系中的插入和删除操作, 我们在数据库中创建存储过程,然后用存储过程模型.由于EF设计视图不支持关系型的模型映射插入和删除操作,我们需要用XML编辑器直接打开.edmx 文件, 在Mappings 节点里 <ModificationFunctionMapping> 标签下,我们添加了插入和删除操作映射到存储过程的代码。

    从Listing 10-25跟踪生成的SQL,我们可以看到,不只是插入或删除 Author 和 Book 两个表, 同时我们也可以看到,存储过程在关系模型中插入和删除操作时被使用。

     

    附:创建示例用到的数据库的脚本文件

     

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  • 原文地址:https://www.cnblogs.com/kid1412/p/5152697.html
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