Entity Framework 6 Recipes 2nd Edition（10-9）譯 -> 在多對多關係中爲插入和刪除使用存儲過程

10-9. 在多對多關係中爲插入和刪除使用存儲過程

問題

想要在一個無載荷的多對多關係中使用存儲過程(存儲過程隻影響關係的鏈接表)

解決方案

假設有一個多對多關係的做者（ Author）表和書籍（ Book）表. 用鏈接表AuthorBook來作多對多關係，如 Figure 10-11.所示:

 

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

當把表生成模型，那麼模型就如Figure 10-12所示：

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

接下來用存儲過程建立插入和刪除操做：

1.在數據庫中，建立如Listing 10-23所示的存儲過程.

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. 右擊模型設計視圖，選擇「從數據庫中更新模型」，選擇 Listing 10-23所建立的存儲過程，單擊「完成」，這樣就把存儲過程添加到了模型裏。

3. 目前版本的EF沒有爲一個關係插入和刪除操做映射的設計視圖，只能用手工去映射, 右擊.edmx 文件，選擇「打開方式」，選擇「XML （文本）編輯器」. 在<AssociationSetMapping> 標籤下插入 Listing 10-24所示的代碼（譯註：根據本身的例子命名修改代碼裏的）

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>

接下來Listing 10-25 代碼演示了插入和刪除操做.你能夠用Sql Profiler來查看當

InsertAuthorBook 和DeleteAuthorBook 存儲過程被EF在更新多對多關係時調用後生成的SQL語句

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("\npress any key to exit...");

            Console.ReadKey();

 

        }

}

SQL Profiler裏跟蹤到的SQL語句以下（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

它是如何工做的？

爲把存儲過程映射到多對多關係中的插入和刪除操做, 咱們在數據庫中建立存儲過程，而後用存儲過程模型.因爲EF設計視圖不支持關係型的模型映射插入和刪除操做,咱們須要用XML編輯器直接打開.edmx 文件， 在Mappings 節點裏 <ModificationFunctionMapping> 標籤下，咱們添加了插入和刪除操做映射到存儲過程的代碼。

從Listing 10-25跟蹤生成的SQL,咱們能夠看到，不僅是插入或刪除 Author 和 Book 兩個表, 同時咱們也能夠看到，存儲過程在關係模型中插入和刪除操做時被使用。

 

附：建立示例用到的數據庫的腳本文件