调用数据库功能的实体框架6 [英] Calling DB Function with Entity Framework 6
问题描述
我按照这些说明添加一个标量函数到我的实体框架6的数据模型。
<一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,我不能够调用LINQ查询中的函数,虽然直接调用该方法的DataContext的工作。
使用(实体上下文=新的实体()){
//这工作。
变种测试1 = context.fn_GetRatingValue(8,9,0).FirstOrDefault();
//这是行不通的。
变种的Test2 =(从context.MediaRatingsř
选择context.fn_GetRatingValue(r.Height,r.Depth,0))了ToList()。
}
第二个查询抛出这个错误。
LINQ到实体无法识别方法System.Data.Entity.Core.Objects.ObjectResult`1 [System.Nullable`1 [System.Single] fn_GetRatingValue(系统。 Nullable`1 [System.Single],System.Nullable`1 [System.Single],System.Nullable`1 [System.Single])的方法,而这种方法不能被翻译成店前pression。
此外,设计师给我这个警告
错误6046:无法生成存储功能fn_GetRatingValue'的函数导入的返回类型。这家商店的功能将被忽略,不会生成函数导入。
我是什么做错了吗?我怎样才能调用数据库功能的LINQ查询中?
另外,如果查询code有时候会针对数据库,有时在内存中执行,有没有办法来调用,在这两种情况下的工作方式的功能?我也有同样的功能的C#版本。
感谢
编辑:这里是我想要使用的功能
公众持股量?的GetValue(浮动?身高,浮?深度,浮动比率){
如果(高度!= NULL ||深!= NULL){
浮HeightCalc =身高? Depth.Value;
浮DepthCalc =深度? Height.Value;
如果(比率℃,)
DepthCalc = DepthCalc +(HeightCalc - DepthCalc)* -ratio;
否则如果(比率大于0)
HeightCalc = HeightCalc +(DepthCalc - HeightCalc)*比例;
回报(浮)Math.Round(HeightCalc * DepthCalc * 0.12,1);
}其他
返回null;
}
它也可以被写成这样一行。这条线可以复制/粘贴无处不在我需要使用它,但是这将产生非常难看code,虽然可以工作。我宁愿保持它作为一个功能。
收益率(浮)Math.Round(
(Height.HasValue Height.Value +(比率大于0((深度?? Height.Value) - Height.Value)*比率:?0):Depth.Value)*
(Depth.HasValue Depth.Value +(比率℃,((身高?? Depth.Value) - Depth.Value)* -ratio:?0):Height.Value)
* 0.12,1);
我找到了答案。虽然我能找到的关于实体框架6中EdmFunctionAttribute是过时很少的文档,我得到这个code工作。
在EDMX文件,IsComposable必须真实在CommandText必须拆除。我只需要在函数声明没有函数导入。
然后,在部分类我的数据上下文,我创造了这个功能。
[DbFunction(NaturalGroundingVideosModel.Store,fn_GetRatingValue)]
公众持股量? DbGetValue(浮动?高度,浮?深度,浮动比率){
清单&LT; ObjectParameter&GT;参数=新的List&LT; ObjectParameter&GT;(3);
parameters.Add(新ObjectParameter(高度,高度));
parameters.Add(新ObjectParameter(深度,深度));
parameters.Add(新ObjectParameter(比率,比));
变种lObjectContext =((IObjectContextAdapter)此).ObjectContext;
无功输出= lObjectContext。
&的createQuery LT;浮动&GT;(NaturalGroundingVideosModel.Store.fn_GetRatingValue(@height,@depth,@ratio),parameters.ToArray())
.Execute(MergeOption.NoTracking)
.FirstOrDefault();
返回输出;
}
我添加功能到MediaRating对象这样我就可以把它无需数据上下文的参考。
VAR的Test2 =(从context.MediaRatingsř
选择r.DbGetValue(r.Height,r.Depth,0))了ToList()。
这个作品!
I followed these instructions to add a scalar function into my Entity Framework 6 data model. How to use scalar-valued function with linq to entity?
However, I'm not able to call the function within a LINQ query, although calling the method directly on the DataContext works.
using (Entities context = new Entities()) {
// This works.
var Test1 = context.fn_GetRatingValue(8, 9, 0).FirstOrDefault();
// This doesn't work.
var Test2 = (from r in context.MediaRatings
select context.fn_GetRatingValue(r.Height, r.Depth, 0)).ToList();
}
The second query throws this error.
LINQ to Entities does not recognize the method 'System.Data.Entity.Core.Objects.ObjectResult`1[System.Nullable`1[System.Single]] fn_GetRatingValue(System.Nullable`1[System.Single], System.Nullable`1[System.Single], System.Nullable`1[System.Single])' method, and this method cannot be translated into a store expression.
Also, the designer is giving me this warning
Error 6046: Unable to generate function import return type of the store function 'fn_GetRatingValue'. The store function will be ignored and the function import will not be generated.
What am I doing wrong? How can I call the database function within a LINQ query?
Also, if the query code sometimes gets executed against the database and sometimes in-memory, is there a way to call the function in a way that works in both cases? I have a C# version of the same function.
Thanks
Edit: Here's the function I'm trying to use.
public float? GetValue(float? Height, float? Depth, float ratio) {
if (Height != null || Depth != null) {
float HeightCalc = Height ?? Depth.Value;
float DepthCalc = Depth ?? Height.Value;
if (ratio < 0)
DepthCalc = DepthCalc + (HeightCalc - DepthCalc) * -ratio;
else if (ratio > 0)
HeightCalc = HeightCalc + (DepthCalc - HeightCalc) * ratio;
return (float)Math.Round(HeightCalc * DepthCalc * .12, 1);
} else
return null;
}
It can also be written in one line like this. This line could be copy/pasted everywhere I need to use it but that would produce very ugly code, although that could work. I'd rather keep it as a function.
return (float)Math.Round(
(Height.HasValue ? Height.Value + (ratio > 0 ? ((Depth ?? Height.Value) - Height.Value) * ratio : 0) : Depth.Value) *
(Depth.HasValue ? Depth.Value + (ratio < 0 ? ((Height ?? Depth.Value) - Depth.Value) * -ratio : 0) : Height.Value)
* .12, 1);
I found the answer. Although I could find very little documentation about Entity Framework 6 in which EdmFunctionAttribute is obsolete, I got this code to work.
In the EDMX file, IsComposable must be True and the CommandText must be removed. I need only the function declaration without the function import.
Then, in a partial class of my data context, I created this function
[DbFunction("NaturalGroundingVideosModel.Store", "fn_GetRatingValue")]
public float? DbGetValue(float? height, float? depth, float ratio) {
List<ObjectParameter> parameters = new List<ObjectParameter>(3);
parameters.Add(new ObjectParameter("height", height));
parameters.Add(new ObjectParameter("depth", depth));
parameters.Add(new ObjectParameter("ratio", ratio));
var lObjectContext = ((IObjectContextAdapter)this).ObjectContext;
var output = lObjectContext.
CreateQuery<float?>("NaturalGroundingVideosModel.Store.fn_GetRatingValue(@height, @depth, @ratio)", parameters.ToArray())
.Execute(MergeOption.NoTracking)
.FirstOrDefault();
return output;
}
I added the function to the MediaRating object so I can call it without needing a reference to the data context.
var Test2 = (from r in context.MediaRatings
select r.DbGetValue(r.Height, r.Depth, 0)).ToList();
This works!
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