实体框架6代码第一个自定义函数 [英] Entity Framework 6 Code First Custom Functions

问题描述

我正在尝试类似的内容：

如何使用带有LINQ的实体的标量值函数？

但是我没有使用EDMX，而只是DbContext和代码。

我遇到过：

< a href =https://codefirstfunctions.codeplex.com/ =nofollow noreferrer> https://codefirstfunctions.codeplex.com/

  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）。

有没有什么办法可以不使用EDMX？我知道你可以构造一个手动查询，但是这不会是优先考虑的，因为我希望使用延迟加载代理等恢复实体，以及构建一个更复杂的查询。

解决方案

您应该可以在 Where 标准中使用标量SQL函数， CodeFirstStoreFunctions

假设您要映射SQL函数[dbo]。[LatLongDistanceCalc]和根据测试套件：

  public class MyDataContext：DbContext 
 {
 protected override void OnModelCreating（DbModelBuilder modelBuilder）
 {
 // ... 
 
 modelBuilder.Conventions.Add（new FunctionsConvention（dbo，this.GetType（）））; 
} 
 
 //CodeFirstDatabaseSchema是一个约定强制模式名称
 //LatLongDistanceCalc是您的函数名称
 
 [DbFunction CodeFirstDatabaseSchema，LatLongDistanceCalc）] 
 public static int LatLongDistanceCalc（int fromLat，int fromLong，
 int toLat，int toLong）
 {
 //不需要提供实现
抛出新的NotSupportedException（）; 
} 
} 
  

的使用将是：

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

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.

解决方案

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)

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