"Range variable name can be inferred only from a simple or qualified name with no arguments" linq 查

Question

我正试图在LinqPad中运行以下查询，第10行不断出现上述错误。

From c in Courses Where c.CourseID = 212
From cc in c.CourseContents Where cc.Active And Not cc.Deleted Order By cc.OrderIndex
Group cc by c Into Content = Group
Select New With {
    c,
    .Content = From cc in Content Select New With {
        .id = cc.CourseContentID,
        .content = If(cc.ContentTypeID = 1, 
        from a in Assessments Where a.AssessmentID = cc.ContentID select a, 
        If (cc.ContentTypeID = 2, from cf in CourseFiles Where cf.CourseFileID = cc.ContentID select cf,
        from ct in CourseTexts Where ct.CourseTextID = cc.ContentID select ct))     
    }
}

我尝试添加select foo=cf，但没有帮助。

如何修复此查询？

Answer 1

我刚刚遇到这个问题，想看看SO上是否有任何悬而未决的问题需要这个答案。

问题所在：

If (cc.ContentTypeID = 2, from cf in CourseFiles Where cf.CourseFileID = cc.ContentID select cf,

现在的情况是最后一个逗号不明确。可以选择多个项目，比如select x, y, z, ...，这样最后一个逗号就可以这样解释，需要另一个标识符。要解决此问题，请在整个From。。。选择语句。

像这样：

If (cc.ContentTypeID = 2, (from cf in CourseFiles Where cf.CourseFileID = cc.ContentID select cf),