为什么我得到这个错误：没有为以下EntitySet / AssociationSet - Entity1指定映射？ [英] Why am I getting this error: No mapping specified for the following EntitySet/AssociationSet - Entity1?

问题描述

我正在使用具有Model First方法的Entity Framework 4。

I'm using Entity Framework 4 with the Model First approach.

我启动了项目，设计了实体并生成了数据库。一切正常。

I started the project, designed the entities and generated the database. Everything worked fine.

然后我需要返回并在我的模型中添加另一个实体。但是，当我拖动一个实体到EDMX我得到这个错误：

Then I needed to go back and add another entity to my model. However, as I drag an entity to the EDMX I get this error:

好的！我只需要将Entity1映射到一个表..但嘿！我正在使用Model First方法，我希望在生成DDL时为我创建表。

Alright! I just need to map Entity1 to a table.. But hey! I'm using Model First approach, I expect it to create the table for me when I generate the DDL.

我如何解决这个错误？

推荐答案

这是因为EF4与模特儿一起工作。

This is because of the way EF4 works with model-first.

您首先创建一个模型第一模型，它处于SSDL不存在的状态。您可以拖动实体，关联它们等等，但是如果您查看EDMX文件上的SSDL，您将看到没有一个实体在SSDL中具有关联的存储表。

When you first create a model-first model, it's in a state that the SSDL does not exist. You can drag entities, associate them and so forth and yet, if you take a look at the SSDL on the EDMX file, you will see that none of the entities have an associated storage table in the SSDL.

当您单击从模型生成数据库上下文菜单项时，会发生更改。令人困惑的部分是，此操作不仅仅是生成DDL脚本。实际上，它将EDMX文件更改为包括SSDL信息。从这一点开始，EDMX文件将进入设计器/ CSDL中的每个实体必须映射到SSDL中的实体的状态。如果没有映射，它将触发编译时错误：

That changes when you click the Generate Database From Model context menu item. The confusing part is that this action does more than simply generating a DDL script. In fact, it changes the EDMX file to include SSDL information. From this point on, the EDMX file will enter a state in which every entity in the designer/CSDL must map to an entity in the SSDL. If one does not map, it will trigger a compile time error:

没有为以下EntitySet / AssociationSet指定的映射 - （EntityName）

No mapping specified for the following EntitySet/AssociationSet - (EntityName)

另一个有趣的事实是，它不会阻止编译的那种错误。确实会生成输出类库。不应该是一个警告或某些东西？

Another interesting fact is that it's not the kind of error that will prevent compilation. It will, indeed, generate the output class library. Shouldn't it be a warning or something?

为了防止这个错误，插入一个新实体之后你要做的所有事情是生成数据库再次从模型这将更新SSDL并修复映射。

To prevent this error, All you have to do after inserting a new entity is to Generate Database From Model again. That will update the SSDL and fix the mappings.

编辑

如果你没有使用模型优先，并且从数据库更新，您还将在DB Server中删除表时出现此错误。这是因为实体框架不会自动删除您的实体。手动删除实体，错误将消失。

If you are not using model-first and you "update from database", you will also have this error in the case you deleted a table in DB Server. This is because Entity Framework will not automatically delete the entity for you. Delete the entity manually and the error will go away.

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