Question

please consider this scenario:

I have data like this :

 Id          Group            Value
 -----------------------------------
 1            1                100
 2            1                120
 3            1                100
 4            2                90
 5            2                105
 6            3                300
 7            4                123
 8            4                110
 9            5                100
 10           5                110

I want to do GroupBy on this data as 1,2,3 place in one group and 4,5 place in another group. How I can do this with LINQ?

thanks

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Edit 1)

I want to place 1,2,3 in one group and 4,5 in another group and perform Count aggregation on them and I get 6 for first group and 4 for secnd group

Answer 1

How about this?

        int[] groupA = { 1, 2, 3 };
        int[] groupB = { 4, 5 };

        var result = data
            .GroupBy(a => groupA.Contains(a.Group) ? "A" : 
                          groupB.Contains(a.Group) ? "B" : 
                          "N/a")
            .Select(a => new
            {
                KEY = a.Key,
                VALUE = a.Count()
            });