集成自定义的方法到LINQ到实体查询

Question

我有一组数据进行一些计算的自定义方法：

private int GetPercentages(int OriginalValue, int TotalValue) 
     { 
      var newValue = (int)Math.Round(((decimal)OriginalValue/(decimal)TotalValue) * 100); 

      return newValue; 
     } 

我需要能够运行的LINQ to Entities查询里面这个方法：

var data = from SurveyResponseModel in db.SurveyResponseModels 
         group SurveyResponseModel by SurveyResponseModel.MemberId into resultCount 
         select new ResultsViewModel() 
         { 
          MemberId = resultCount.Key, 
          PatientFollowUpResult = db.SurveyResponseModels.Count(r => r.PatientFollowUp), 
          PatientFollowUpResultPct = GetPercentages(db.SurveyResponseModels.Count(r => r.PatientFollowUp),totalResponsesResult), 
          ChangeCodingPracticeResult = db.SurveyResponseModels.Count(r => r.ChangeCodingPractice), 
    }; 

我需要在查询中约20多行运行这个所以就坚持它内联似乎不是一个很好的选择。据我所知，它需要被转换成SQL语法，但有别的像这样，我还能做什么？

Answer 1

你需要做一个lambda表达式计算这样的比例：

Expression<Func<int, int, int>> calcPercentage = 
    (OriginalValue, TotalValue) => (int)Math.Round(((decimal)OriginalValue/(decimal)TotalValue) * 100); 

而且使用这样的：

var data = from SurveyResponseModel in db.SurveyResponseModels.ToExpandable() 
      group SurveyResponseModel by SurveyResponseModel.MemberId into resultCount 
      select new ResultsViewModel() 
      { 
       MemberId = resultCount.Key, 
       PatientFollowUpResult = db.SurveyResponseModels.Count(r => r.PatientFollowUp), 
       PatientFollowUpResultPct = calcPercentage.Invoke(db.SurveyResponseModels.Count(r => r.PatientFollowUp), totalResponsesResult), 
       ChangeCodingPracticeResult = db.SurveyResponseModels.Count(r => r.ChangeCodingPractice), 
      }; 

更多关于LINQ中调用函数信息查询here。