Question

Given:

var detailList = new List<DetailItem>();

Where:

class DetailItem
{
    string A;
    MyType B;
}

Can a LINQ query group on field A into the following data structure:

class GroupItem
{
    string A;
    List<MyType> AllBsWithinA;
}



IEnumerable<GroupItem> linqQuery = detailList.SomeLinqMagic(…);

The data in question is all memory based so this is a LINQ to Objects question.

Answer 1

This looks straightforward, unless I missed your meaning:

IEnumerable<GroupItem> linqQuery = detailList
    .GroupBy(i => i.A)
    .Select(g => new GroupItem() 
    { 
        A = g.Key, 
        AllBsWithinA = g.Select(i => i.B).ToList() 
    });