LINQ - Group To Model

Question

I have a list like below with more column. First two column is for entity A and second two column is for entity B. As you can see there is one to many relationship between these entities. So, I want to group this list to custom model.

    QID ORDERNUMBER OPID  POINT
    1888    1       6902    4
    1888    1       6903    3
    1888    1       6904    2
    1888    1       6905    1
    1889    2       6906    4
    1889    2       6907    3
    1889    2       6908    2
    1889    2       6909    1
    1890    3       6910    4
    1890    3       6911    3
    1890    3       6912    2
    1890    3       6913    1

First two column for Question object and other two column is for Options object list. This is my model

public class MyModel
{
    public Question Question { get; set; }
    public List<Option> Options { get; set; }
}

I need to group above table by QID. After that I need to take group key to Question object and assign QID's groups to list of Option object.

Simple demonstrade for one instance of MyModel should be;

MyModel > Question > QID:1888
                     ORDERNUMBER:1

        > Options >  [0] : OPID:6902
                           POINT:4
                     [1] : OPID:6903
                           POINT:3
                     [2] : OPID:6904
                           POINT:2
                     [3] : OPID:6905
                           POINT:1

@Fabjan Actually, I am newbie on this query things. I tried simple GroupBy queries but could not handle. — berkan, Sep 12 '18 at 12:57
Possible duplicate of [Using group by on multiple columns](https://stackoverflow.com/questions/2421388/using-group-by-on-multiple-columns) — Andrew, Sep 12 '18 at 12:59

score 3 · Accepted Answer · answered Sep 12 '18 at 12:59

Firstly, GroupBy QID, ORDERNUMBER, then, for each group, init the question and his questions

var models = list.GroupBy(q => new { q.QID, q.ORDERNUMBER})
    .Select(g => new Model() 
                { 
                   Question = new Question() { QID = g.Key.QID, ORDERNUMBER =g.Key.ORDERNUMBER} , 
                   Options  = new List<Option>(g.ToList().Select(i => new Option() { OPID = i.OPID, POINT = i.POINT })) 
                })

LINQ - Group To Model

1 Answers1