实体框架6 code首先自定义功能 [英] Entity Framework 6 Code First Custom Functions

问题描述

我想类似这样的：

<一个href=\"http://stackoverflow.com/questions/12481868/how-to-use-scalar-valued-function-with-linq-to-entity\">How使用标量值函数使用LINQ到实体？

不过我不使用EDMX，而只是和的DbContext code第一。

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

我遇到这样的：

的https：//$c$cfirstfunctions.$c$cplex.com/

但是使用不适合。我想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)

在哪里它会调用一个标量函数（LatLongDistanceCalc）SQL Server上。

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

有没有办法做到这一点，而无需使用EDMX？我知道，你可以建立一个手动查询，但因为我要带回实体延迟加载代理等，以及建立一个更复杂的查询，这将不会是prefereable。

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

您应该能够在你的其中，审核规定使用一个标量SQL函数的 codeFirstStoreFunctions

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

假设要映射的SQL函数[DBO]。[LatLongDistanceCalc]，并且根据<一href=\"https://$c$cfirstfunctions.$c$cplex.com/SourceControl/latest#$c$cFirstStoreFunctionsSamples/ScalarFunctionSample.cs\"相对=nofollow>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();
    }
}

使用然后将：

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

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