实体框架-使用TPH按ICollection类型过滤LINQ | 使用TPH按ICollection类型过滤LINQ

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问题描述

我有一个类Main，它具有各种类型的ICollection(SubA和SubB，父类是Parent).我需要编写一个LINQ查询，该查询使用每个表层次结构基于EF中的这些子类型进行过滤. TPH不允许直接查询Type列，因此我试图找出一种解决方法.我在Parent上有一个方法来获取类型字符串. LINQ不支持此功能.

I'm have a class, Main, that has an ICollection of various types (SubA and SubB, parent class is Parent). I need to write a LINQ query that filters based on these subtypes in EF using table-per-hierarchy. TPH doesn't allow querying the Type column directly, so I'm trying to figure out a workaround. I have a method on Parent to get the type string. LINQ doesn't support this, however.

如何从Main执行LINQ查询以筛选每个子类型(SubA和SubB)以及该子项的另一个属性?

How can I perform a LINQ query from Main to filter on the type of each child (SubA and SubB), as well as one additional property of the child?

这是获取类型的类方法:

This is the class method to get the type:

public virtual string ReturnType()
{
    return GetType().BaseType.Name;
}

这是我正在尝试的LINQ查询，但由于LINQ不支持ReturnType()而失败.

This is the LINQ query I was attempting, but fails because ReturnType() isn't supported in LINQ.

// Main query defined elsewhere in function
query = query.Where(main => main.children.All(child =>
                   (child.ReturnType() == "MS" || child.ReturnType() == "TL") &&
                   child.StatusId != 4);

推荐答案

您可以执行以下操作:

query = query.Where(m => m.StatusId != 4 && (m is SubA || m is SubB));

或更复杂的使用OfType:

var subQuery = query.Where(m => m.StatusId != 4);
query = subQuery.OfType<SubA>()
                .Cast<Main>()
                .Union(subQuery.OfType<SubB>().Cast<Main>());

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