c＃使用linq按数据表中的多个列进行分组 [英] c # using linq to group by multiple columns in a datatable

问题描述

我在datatable中有三列：string，DateTime和decimal。我想通过字符串和十进制列进行分组，对于分组的行，我想将十进制值相加。我知道如何做总和部分，但是如何在数据表中分组两个不同的列？

I have three columns in a datatable: string, DateTime, and decimal. I want to group by the string and decimal column, and for the rows grouped I want to sum the decimal values. I know how to do the sum part, but how do you group two different columns in a datatable?

这是迄今为止我的代码无法正常工作的代码： / p>

This is my code so far which doesn't work properly:

var newSort = from row in objectTable.AsEnumerable()
              group row by new {ID = row.Field<string>("resource_name"), time1 = row.Field<DateTime>("day_date")} into grp
              orderby grp.Key
              select new
              {
                 resource_name1 = grp.Key.ID,
                 day_date1 = grp.Key.time1,
                 Sum = grp.Sum(r => r.Field<Decimal>("actual_hrs"))
              };

推荐答案

我不认为你给我们全文除了 orderby 不使用匿名类型（您提供的代码不会编译），您的查询应该按照您想要的方式工作。我只是把它放在LINQPad中：

I don't think you're giving us the full story. Other than orderby not working with anonymous types (the code you gave wouldn't have compiled), your query should work the way you want. I just put this in LINQPad:

var objectTable = new DataTable();
objectTable.Columns.Add("resource_name",typeof(string));
objectTable.Columns.Add("day_date",typeof(DateTime));
objectTable.Columns.Add("actual_hrs",typeof(decimal));
objectTable.Rows.Add(1, DateTime.Today, 1);
objectTable.Rows.Add(2, DateTime.Today, 2);

var newSort = from row in objectTable.AsEnumerable()
            group row by new {ID = row.Field<string>("resource_name"), time1 = row.Field<DateTime>("day_date")} into grp
            select new
                {
                    resource_name1 = grp.Key.ID,
                    day_date1 = grp.Key.time1,
                    Sum = grp.Sum(r => r.Field<Decimal>("actual_hrs"))
                };
newSort.Dump();

...我得到这些结果：

... and I got these results:

resource_name1 | day_date1            | Sum
1              | 7/1/2011 12:00:00 AM | 1 
2              | 7/1/2011 12:00:00 AM | 2 

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