EF Core 3 x.Contains() 在表达式中，其中 x 是 ICollection [英] EF Core 3 x.Contains() in expression where x is ICollection

问题描述

我有以下数据层设置:

public class Repository : IRepository {

    private readonly MyDbContext _dbContext;

        public List<Meter> Search(Expression<Func<Meter,bool>> criteria)
            IQueryable<Meter> results = _dbContext.Meters;
            return results.Where(criteria).ToList();
        }
    }
}

... from a client class:

IRepository _repository;

public void ClientMethod () {

    ICollection<int> ids = new List<int>() {1, 2, 3);
    var results = _repository.Search(c=> ids.Contains(c.Id)); // This throws exception

}

这导致异常:

表达式 Where(source: DbSet, predicate: (m) =>(未处理的参数: __ids_0).Contains(m.Id))' 不能翻译.要么以可翻译的形式重写查询，或通过插入调用显式切换到客户端评估AsEnumerable()、AsAsyncEnumerable()、ToList() 或 ToListAsync()

expression Where(source: DbSet, predicate: (m) => (Unhandled parameter: __ids_0).Contains(m.Id))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync()

但是如果我将集合引用更改为 IEnumerable 或 List，它会起作用:

But if I change the collection reference to IEnumerable or List, it works:

public void ClientMethod () {

    // This works
    List<int> ids = new List<int>() {1, 2, 3);
    var results = _repository.Search(c=> ids.Contains(c.Id)); 

    // This works
    IEnumerable<int> ids = new List<int>() {1, 2, 3);
    var results = _repository.Search(c=> ids.Contains(c.Id)); 
}

为什么它不适用于 ICollection，但适用于 IEnumerable 和 List?我的许多客户端方法都将 ICollection 作为参数.

Why is it not working for ICollection, but it does for IEnumerable and List? Many of my client methods take an ICollection as a parameter.

我使用的是 EF Core 3.0，但我相信我在 2.1 中遇到了同样的问题，它只是在客户端上评估时没有抛出.

I'm using EF Core 3.0 but I believe I had the same problem in 2.1, it just didn't throw as it evaluated it on the client instead.

推荐答案

这是 3.1 中修复的已知错误.由于查询管道重写后的所有回归，3.0 几乎无法使用.

This is a known bug fixed in 3.1. 3.0 is almost unusable due to all regressions after the query pipeline rewrite.

我建议在 github 上关注 ef 核心的问题跟踪器.

I recommend following the issue tracker on github for ef core.

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