linq查询中的“只能从没有参数的简单或限定名称推断范围变量名”错误

我试图在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

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我如何解决这个问题？

我刚刚遇到了这个问题，我想看看是否有任何悬而未决的问题需要回答

解决问题的方法是：

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

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

发生的事情是最后一个逗号不明确。可以选择多个项目，如选择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…Select语句周围加上括号

像这样：