Entity Framework 6 Code First Custom Functions

问题

I'm trying something similar to this:

How to use scalar-valued function with linq to entity?

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

I've come across this:

https://codefirstfunctions.codeplex.com/

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)

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

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.

回答1:

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

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();
    }
}

usage would then be:

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

来源：https://stackoverflow.com/questions/29517627/entity-framework-6-code-first-custom-functions

标签

linq

entity-framework

entity-framework-6