使用GroupBy和Sum进行Linq查询，并返回未分组的值

如何解决使用GroupBy和Sum进行Linq查询，并返回未分组的值

当尝试编写linq查询以对一些数据进行分组和求和时，我收到以下错误：

CS1061'CM_Records'不包含'Sum'的定义，并且没有 扩展方法'Sum'接受类型为'CM_Records'的第一个参数 可以找到

var results = (from r in CM_Records
      join sub in CM_Records on r.Id equals sub.Id
      select new {R = r,S = sub}
      into joined
      group joined by new
      {
         label = joined.R.ServiceDateTime.Value.Month + "/" + joined.R.ServiceDateTime.Value.Day + "/" + joined.R.ServiceDateTime.Value.Year,joined.R.CategoryId
      }
      into grouped
      select grouped.Select(g =>
         new
         {
            grouped.Key.label,grouped.Key.CategoryId,Value = g.S.Sum(x => int32.Parse(x.Value)),//This is the line that fails
            //Value = g.S.Value,//Uncomment this line and comment the line above to get the following output.
            ServiceTime = Convert.ToDateTime(g.S.ServiceDateTime).ToShortTimeString()
         })
   )
   .SelectMany(x => x);

我知道Sum要求对象为IQueryable，只是不确定如何在此查询中完成该任务而不破坏其他内容。 请记住，此查询被设置为变量，然后结合使用以在C＃中生成JSON对象。

无SUM的电流输出：

Label    Cat.  Value ServiceTime
1/1/2017    439960  121 9:00 AM
1/1/2017    439960  131 5:00 PM
1/1/2017    439960  213 11:45 AM
1/1/2017    439960  210 10:20 AM
1/1/2017    439961  143 9:30 AM
1/1/2017    439994  92  9:30 AM
1/1/2019    439989  0   7:00 PM
1/1/2020    439968  172 7:00 PM
1/10/2018   439968  124 7:00 PM
1/10/2018   439969  120 7:00 PM

我需要将以上结果按“标签”列进行分组，并将值相加。

解决方法

尝试此查询：

var results = (from r in CM_Records
               join sub in CM_Records on r.Id equals sub.Id
               select new {R = r,S = sub}
               into joined
               group joined by new
               {
                  label = joined.R.ServiceDateTime.Value.Month + "/" + joined.R.ServiceDateTime.Value.Day + "/" + joined.R.ServiceDateTime.Value.Year,joined.R.CategoryId
               }
               into grouped
               select new
               {
                  grouped.Key.label,grouped.Key.CategoryId,Value = grouped.ToList().Select(x => x.S.value).Sum()
               }).ToList();

包括ServiceTime并没有多大意义，除非您决定选择max，min或类似的东西。