使用NHibernate从投影中获取子类类型 [英] Get subclass type from projection with NHibernate

问题描述

我正在尝试对名为 Log 的类型进行投影.日志引用了名为 Company 的超类.每个公司类型都与每个子类的表相对应.

I am trying to do a projection on a type called Log. Log references a superclass called Company. Each company type is mapped with table per subclass.

在日志上进行投影时，我能否获得公司的类型? 我目前在每个子类上都有一个Enum属性(未映射)，因此可以对Company类型执行切换，但是由于未映射到任何东西，因此无法对其进行投影.

Is it possible for me to get the type of Company when I do a projection on Log? I currently have an Enum property (which is not mapped) on each subclass, so I can perform switches on Company types, but since it is not mapped to anything, I can't do a projection on it.

我已经尝试过Projections.Property("log.Company.class")，但它不起作用:(

I have tried Projections.Property("log.Company.class") but that does not work :(

PS:对于这个问题，我找不到很多合适的标签.如果有人想使用更具体的标签，请告诉我.

PS: I couldn't find a lot of appropriate tags for this question. If anyone have an idea for more specific tags, please tell me.

推荐答案

您可以执行以下操作...

You can do the following...

session.CreateCriteria<Log>()
       .CreateAlias("Company", "company")
       .SetProjection(Projections.Property("company.class"))

但是该投影只能用于过滤和排序； NHibernate不会在结果集中返回System.Type(它返回一个整数，供内部使用).

But that projection can only be used for filtering and ordering; NHibernate will not return the System.Type in the result set (it returns an integer, which is used internally).

如果您需要了解公司的具体类型，则可以执行以下操作:

If what you need is to know the concrete type of the Company, you can do the following:

var logs = session.CreateCriteria<Log>()
                  .SetFetchMode("Company", FetchMode.Join) //avoid SELECT N+1
                  .List<Log>()

然后，获取每一行的类型:

And then, to retrieve the type for each row:

foreach (var log in logs)
    string companyClassName = session.GetEntityName(log.Company);

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