EF GroupBy多个字段

GroupBy根据多个字段分组使用方式：

一、使用扩展方法

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类型

Dictionary 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);

更多参考：

关于EF上线文异常问题整理

TransactionScope线程安全问题整理

EF日期格式筛选