调用的方法的LINQ查询的选择部分内 [英] Call a method inside the select part of a LINQ query

问题描述

我有以下的LINQ查询：

I have the following linq query:

var file = (from p in database.tblFile
            join o in database.tblFileVersion on p.fldFileID equals o.fldFileID
            join t in database.tblFileAttachments on p.fldFileID equals t.fldFileID
            where p.fldFileID == team.Key
            where o.fldVersionNo == highestVersion
            select new UserDashboardFile
            {
                Filename = p.fldFilename,
                VersionNumber = o.fldVersionNo,
                FileID = team.Key,
                Type = GetFileType(t.fldTableName),
            }).Single();

GetFileType是返回枚举类型的方法。有没有语法错误，但是当我运行该项目（这是一个MVC 4 web项目），我收到以下错误：

GetFileType is a method that returns an enumeration type. There is no syntax error but when I run the project (it is an mvc 4 web project) I receive the following error:

LINQ到实体无法识别方法
位DCIS.Code.UserDashboardFileType GetFileType（System.String）'方法，
和这种方法不能被翻译成商店表达

LINQ to Entities does not recognize the method 'DCIS.Code.UserDashboardFileType GetFileType(System.String)' method, and this method cannot be translated into a store expression.

我想，这个查询不能被翻译成T-SQL查询，但我不知道如何改变我的查询，以避免上述错误。在此先感谢...

I imagine that this query cannot be translated into a t-sql query but I do not know how to change my query in order to avoid the above error. Thanks in advance...

推荐答案

您可以先选择匿名对象，然后构建 UserDashboardFile 。

You can select anonymous object first and then construct UserDashboardFile.

var file = (from p in database.tblFile
            join o in database.tblFileVersion on p.fldFileID equals o.fldFileID
            join t in database.tblFileAttachments on p.fldFileID equals t.fldFileID
            where p.fldFileID == team.Key
            where o.fldVersionNo == highestVersion
            select new 
            {
                Filename = p.fldFilename,
                VersionNumber = o.fldVersionNo,
                FileID = team.Key,
                FldTableName = t.fldTableName
            }).Single();
var udFile = new UserDashboardFile { ..., Type = GetFileType(file.FldTableName) };

您也可以拨打 .AsEnumerable（）之前选择以防止 GetFileType 在SQL进行翻译。

Also you can call .AsEnumerable() before select to prevent GetFileType to be translated in sql.

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