9

可能重复：
SQL 级别函数是否可用于 LINQ to Entity 查询？

我有一个标量函数，可以获取两点之间的距离，我想用它来查询最近的记录到点。标量函数适用于 linq to sql 但因 EF 失败

标量函数

USE [GeoData]
GO

/****** Object:  UserDefinedFunction [dbo].[DistanceBetween]    Script Date: 09/18/2012 19:40:44 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO



CREATE FUNCTION [dbo].[DistanceBetween](@Lat1 as real,
@Long1 as real, @Lat2 as real, @Long2 as real)
RETURNS real
AS
BEGIN

DECLARE @dLat1InRad as float(53);
SET @dLat1InRad = @Lat1;
DECLARE @dLong1InRad as float(53);
SET @dLong1InRad = @Long1;
DECLARE @dLat2InRad as float(53);
SET @dLat2InRad = @Lat2;
DECLARE @dLong2InRad as float(53);
SET @dLong2InRad = @Long2 ;

DECLARE @dLongitude as float(53);
SET @dLongitude = @dLong2InRad - @dLong1InRad;
DECLARE @dLatitude as float(53);
SET @dLatitude = @dLat2InRad - @dLat1InRad;
/* Intermediate result a. */
DECLARE @a as float(53);
SET @a = SQUARE (SIN (@dLatitude / 2.0)) + COS (@dLat1InRad)
* COS (@dLat2InRad)
* SQUARE(SIN (@dLongitude / 2.0));
/* Intermediate result c (great circle distance in Radians). */
DECLARE @c as real;
SET @c = 2.0 * ATN2 (SQRT (@a), SQRT (1.0 - @a));
DECLARE @kEarthRadius as real;
/* SET kEarthRadius = 3956.0 miles */
SET @kEarthRadius = 6376.5;        /* kms */

DECLARE @dDistance as real;
SET @dDistance = @kEarthRadius * @c;
return (@dDistance);
END

GO

我添加了一个 ado.net 实体模型，从数据库中更新了模型并选择了距离

 <Function Name="DistanceBetween" ReturnType="real" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="true" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
      <Parameter Name="Lat1" Type="real" Mode="In" />
      <Parameter Name="Long1" Type="real" Mode="In" />
      <Parameter Name="Lat2" Type="real" Mode="In" />
      <Parameter Name="Long2" Type="real" Mode="In" />
    </Function>

我做了一个部分类并写了这个方法

public partial class GeoDataEntities
{
    [EdmFunction("GeoDataModel.Store", "DistanceBetween")]
    public double DistanceBetween(double lat1, double lon1, double lat2, double lon2)
    {
        throw new NotImplementedException();
    }
}

我多次尝试使用此代码查询函数，但出现错误

var NParcel = db.geoAddresses.Where(g=> db.DistanceBetween(21.5,39.5, g.lat,g.lon) < 20);

当我尝试count使用foreachNParcel 时，我收到此错误

'EFSample.GeoDataEntities' 类型上的指定方法 'Double DistanceBetween(Double, Double, Double, Double)' 无法转换为 LINQ to Entities 存储表达式。

和堆栈跟踪

在 System.Data.Objects.ELinq.ExpressionConverter.ThrowUnresolvableFunction(Expression Expression) 在 System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.FunctionCallTranslator.TranslateFunctionCall(ExpressionConverter parent, MethodCallExpression call, EdmFunctionAttribute functionAttribute) 在 System.Data.Objects.ELinq .ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) 在 System.Data.Objects.ELinq.ExpressionConverter.BinaryTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq) 在 System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)在 System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda（LambdaExpression lambda，DbExpression 输入）在 System.Data.Objects.ELinq。System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) 在 System.Data. .Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) 在 System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) 在 System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.AggregateTranslator.Translate( ExpressionConverter 父级，MethodCallExpression 调用）在 System.Data.Objects.ELinq.ExpressionConverter。System.Data.Objects.ELinq.ExpressionConverter.Convert() 在 System.Data.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable) 的 MethodCallTranslator.TypedTranslate(ExpressionConverter parent，MethodCallExpression linq)1 forMergeOption) at System.Data.Objects.ObjectQuery1.GetResults（在 System.Linq.Enumerable.Single[TSource] 处为 Nullable 1 forMergeOption) at System.Data.Objects.ObjectQuery1.System.Collections.Generic.IEnumerable.GetEnumerator()（IEnumerable 1 source) at System.Linq.Queryable.Count[TSource](IQueryable1 源）

4

1 回答 1

25

这是您的操作方法：

第 1 步：在 edmx 中

      <Function Name="DistanceBetween" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
      <CommandText>
        select dbo.DistanceBetween(@lat1,@long1,@lat2,@long2)
      </CommandText>
      <Parameter Name="Lat1" Type="real" Mode="In" />
      <Parameter Name="Long1" Type="real" Mode="In" />
      <Parameter Name="Lat2" Type="real" Mode="In" />
      <Parameter Name="Long2" Type="real" Mode="In" />
    </Function>

第二步：导入函数

  1. 双击edmx
  2. 在模型浏览器视图中，展开GeoDataModel.Store（可以命名不同）
  3. 扩张stored procedures /function
  4. 双击DistanceBetween
  5. Scalars = Single
  6. 点击确定

第 3 步：在 C# 中：

    GeoDataEntities db = new GeoDataEntities();
    var first = db.DistanceBetween(234, 2342, 424, 243).First().Value;

请注意， IsComposable="false"不ReturnType，不要忘记添加：

      <CommandText>
        select dbo.DistanceBetween(@lat1,@long1,@lat2,@long2)
      </CommandText>

希望有帮助....

于 2012-09-19T19:36:06.843 回答