Grouping in nested sortedlist vb.net

Question

I have a list of objects.

    Class Sales
      Public Property CustomerName As String
      Public ItemName As String
      Public Quantity As Double
      ....other details...
    End Class

    Dim records As IList(Of Sales)

Any idea how I can group them by CustomerName, followed by ItemName and arrange them into a nested sorted list?

The data type that I want to arrange them to is as follow:-

    Dim collection As SortedList(Of String, SortedList(Of String, List(Of Sales)))

The key in the outer sortedList would be CustomerName.

The key in the inner sortedList would be ItemName.

Thanks very much for your help!

Answer 1

It's simple:

Dim collection As New SortedList(Of String, SortedList(Of String, List(Of Sales)))( _
    records _
        .GroupBy(Function (r) r.CustomerName) _
        .Select(Function (x) New With { .CustomerName = x.Key, .Items = x.GroupBy(Function (i) i.ItemName) }) _
        .ToDictionary( _
            Function (x) x.CustomerName, _
            Function (x) New SortedList(Of String, List(Of Sales))(x.Items.ToDictionary(Function (y) y.Key, Function (y) y.ToList()))))