無法隱式轉換類型「匿名類型＃1 []」到「INT []」

Question

我有以下情形中，我試圖用分組方法

//Gets MulitCourseIds from db of selected CourseIds 
     int[] _hasListCourseIds = (from mcd in _db.MultiCourseDetails 
           where _lstCourseIds.Contains(mcd.CourseId.Value) 
           group mcd.MultiCourseId by mcd.MultiCourseId into g 
           select new { multiCourseId = g.Key }).ToArray(); 
            ************ error is occuring here********** 

     if (_hasListCourseIds.Count > 0) 
     { 
      //Checks the count of courseIds from the db and selected courseIds 
      foreach (var _multiCourseId in _hasListCourseIds) 
      {     
       var _courseCount = _db.MultiCourseDetails          
            .Where(x => x.MultiCourseId == _multiCourseId) 
            .Count(); 
       if (_courseCount == _lstCourseIds.Count) 
       { 
        return true; 
       } 
      } 

我得到的錯誤，以獲取數據庫信息

無法隱式轉換類型 '匿名類型＃1 []' 到 'INT []'

提高代碼的任何建議，也邀請了..

Answer 1

問題是您正在投影anonymous類型，但將其分配給int陣列。既然你是突出一個屬性不在此處需要一個匿名類型： -

int[] _hasListCourseIds = (from mcd in _db.MultiCourseDetails 
          where _lstCourseIds.Contains(mcd.CourseId.Value) 
          group mcd.MultiCourseId by mcd.MultiCourseId into g 
          select g.Key).ToArray(); 

我認爲MultiCourseId是int。