Entity Framework 6 Code First 自定义函数 [英] Entity Framework 6 Code First Custom Functions

问题描述

我正在尝试类似的方法:

I'm trying something similar to this:

如何在 linq 中使用标量值函数实体?

但是我没有使用 EDMX，而是首先使用 DbContext 和代码.

However I'm not using EDMX, but instead just DbContext and code first.

我遇到过这个:

https://codefirstfunctions.codeplex.com/

但用法不合适.我想要实现的是能够做到这一点:

But the usage isn't suitable. What I am trying to achieve is to be able to do this:

var locations = context.Locations.Where(e => Functions.LatLongDistanceCalc(e.Lat, e.Long, lat, long) >= 10)

它将在 SQL Server 上调用标量函数 (LatLongDistanceCalc) 的位置.

Where it will call a scalar function (LatLongDistanceCalc) on SQL Server.

有没有不使用 EDMX 的方法来做到这一点?我知道您可以构建手动查询，但这不是首选，因为我想使用延迟加载代理等返回实体以及构建更复杂的查询.

Is there any way to do this without using EDMX? I know that you can construct a manual query but this wouldn't be prefereable because I want to bring back entities with lazy loading proxies etc as well as building up a more complex query.

推荐答案

您应该能够在带有 CodeFirstStoreFunctions

You should be able to use a scalar SQL function in your Where criterias with CodeFirstStoreFunctions

假设你想映射 SQL 函数 [dbo].[LatLongDistanceCalc]，并根据 测试套件:

Assuming you want to map SQL function [dbo].[LatLongDistanceCalc], and according to the test suite:

public class MyDataContext: DbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
       //...

       modelBuilder.Conventions.Add(new FunctionsConvention("dbo", this.GetType()));
    }

    // "CodeFirstDatabaseSchema" is a convention mandatory schema name
    // "LatLongDistanceCalc" is the name of your function

    [DbFunction("CodeFirstDatabaseSchema", "LatLongDistanceCalc")]
    public static int LatLongDistanceCalc(int fromLat, int fromLong,
                                                       int toLat, int toLong)
    {
       // no need to provide an implementation
       throw new NotSupportedException();
    }
}

然后使用:

context.Locations
       .Where(e => MyDataContext.LatLongDistanceCalc(e.Lat, e.Long, lat, long) >= 10)

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