GroupBy根據多個字段分組使用方式：

一、使用擴展方法

query.GroupBy(q => new { q.Year, q.Month })    .Select(q => new    {        Year = q.Key.Year,        Month = q.Key.Month,        BuildAmount = q.Sum(i => i.BuildAmount),        RecAmount = q.Sum(i => i.RecAmount),        Amount = q.Sum(i => i.Amount),        RealAmount = q.Sum(i => i.RealAmount)    });二、Linq方式
        var query = from l in list                      group l by new { l.Name, l.BatNum } into g                      select new                      {                          Name = g.Key.Name,                          Count = g.Sum(a => a.Count),                          BatNum = g.Key.BatNum                      };  
三、生成KeyValue類型
Dictionary<string,decimal> buildList = _build.FindList().GroupBy(q => q.SaleCode)        .Select(q => new { Code = q.Key, ReaAmount = q.Sum(i => i.RealAmount) })        .ToDictionary(q => q.Code, q => q.ReaAmount);
更多參考：
關于EF上線文異常問題整理
TransactionScope線程安全問題整理
EF日期格式篩選