从IQueryable到IEnumerable

问题描述

对于所有f＃摇杆来说，这应该是一个快速的选项，但此刻让我陷于困境。

this should be a quick one for all you f# rockers, but it's got me stuck at the moment.

我有一个F＃类型，试图实现ac＃接口

I've got an F# type which I'm trying to get to implement a c# interface

public interface ICrudService<T> where T: DelEntity, new()
{
    IEnumerable<T> GetAll();
}

这是在c＃中的实现方式：

here's how it's implemnted in c#:

public IEnumerable<T> GetAll()
{
    return repo.GetAll();
}

repo.GetAll 返回 IQueryable ，但是c＃编译器知道足以转换为 IEnumerable ，因为 IQueryable< T> ; ：IEnumerable< T> 。但是在F＃中，编译器无法运行它，而我尝试了几次尝试将其正确转换

repo.GetAll returns an IQueryable, but the c# compiler knows enough to convert to IEnumerable because IQueryable<T> : IEnumerable<T>. but In F# the compiler can't work it and I've tried a few attempt to cast it correctly

type CrudService<'T when 'T :(new : unit -> 'T) and 'T :> DelEntity>(repo : IRepo<'T>) =
    interface ICrudService<'T> with
         member this.GetAll () =
            repo.GetAll<'T>

这给我一个类型不匹配的错误

this is giving me a type mismatch error

推荐答案

您需要转换为 IEnumerable<'T> ：

type CrudService<'T when 'T :(new : unit -> 'T) and 'T :> DelEntity>(repo : IRepo<'T>) =
        interface ICrudService<'T> with
             member this.GetAll () =
                repo.GetAll() :> IEnumerable<'T>

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