从具有一对多关系的多个表组成的模型中获取数据
我有一个关于 ASP.NET MVC 模型的相对简单的问题。
我有一个基于以一对多关系链接的两个表的模型。
table AnimalGroup(ID,name)
table AnimalSubGroup(ID,name,AnimalGroupID)
每个 AnimalGroup 都有任意数量的 AnimalSubgroup。
如何迭代每个 AnimalGroup 的 AnimalSubGroup 并获取 AnimalSubGroup.name（例如）？我是 ASP.NET MVC 新手，一直在关注各种教程，但是虽然它们非常适合设置基本应用程序并从单个表中获取结果，但我对如何获取结果感到困惑来自同一模型中链接的多个表。我已经看到对 ViewModel 作为解决方案的引用，但似乎 ViewModel 对于将两个不相关表中的数据放入单个视图中更有用。
提前致谢。
I've got a relatively simple question about asp.net MVC models.
I've got a model based on two tables that are linked in a one-to-many relationship.
table AnimalGroup(ID,name)
table AnimalSubGroup(ID,name,AnimalGroupID)
Each AnimalGroup has any number of AnimalSubgroups.
How do I iterate through each AnimalGroup's AnimalSubGroups and get AnimalSubGroup.name (for example)? I'm new to asp.net MVC and have been following various tutorials, but while they're excellent for getting a basic application set up and getting results out of a single table, I'm stuck as to how I'd get results from several tables linked in the same model. I've seen references to ViewModel as a solution, but it seems that ViewModel is more useful for putting data from two unrelated tables into a single View.
Thanks in advance.
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第一的。您的数据库中是否定义了外键？如果是，edmx 模型生成器将定义所有连接。如果没有，请立即执行。完成后，您可以通过以下方式选择子组名称：
直接从上下文中获取：
context.AnimalSubGroupSet.Where(sg => sg.AnimalGroupID = requestAnimalGroupID).Select(sg => sg.Name).ToList;
从 AnimalGroup 获取：
animalGroup.AnimalSubGroups.Select(sg => sg.Name);
此代码可能需要调整，但不应太复杂。
First. Do you have foreign keys defined in your database? If yes, edmx model generator will define all conections. If not, do it right now. When it is done, you can select subgroup name by:
Taking it directly from context:
context.AnimalSubGroupSet.Where(sg => sg.AnimalGroupID = requestedAnimalGroupID).Select(sg => sg.Name).ToList;
Taking it from AnimalGroup:
animalGroup.AnimalSubGroups.Select(sg => sg.Name);
This code may need adjustments, but they shouldn't be complicated.
也许您应该看一下 LINQ 的 SelectMany 查询运算符。这对一对多数据表关系进行子迭代。请注意，您可以链接 SelectMany 调用：
这假设您的数据表中有外键关系。
Perhaps you should take a look at LINQ's SelectMany query operator. This sub-iterates over one-to-many data table relationships. Note that you can chain SelectMany calls:
This assumes that you have foreign key relationships in your data tables.