Implementing Custom GroupBy function in VB.Net - vb.net

Question

I'm trying to implement a GroupBy function in such a way that it's generic and we don't end up having to keep adding properties every time the client wants something added/changed (yes, I know there's other options. Limited time/budget restrict the scope to this or hard-coding more properties, so I'm trying to opt for the better solution).
Currently I have the following;
<!-- language: lang-vb -->
Dim groupByColumns = New Dictionary(Of String, Boolean) From {
{"Col1", True},
{"Col2", False},
...
}
Dim groupedData = data.GroupBy(Function(r)
Dim groupingResult = New List(Of KeyValuePair(Of String, Object))
For Each column In groupByColumns
Dim groupingValue As Object = Nothing
If column.Value Then
groupingValue = TypeDescriptor.GetProperties(r).Item(grouping.Key).GetValue(r)
End If
groupingResult.Add(New KeyValuePair(Of String, Object)(column.Key, groupingValue))
Next
Return groupingResult
End Function)
If I then do an OrderBy or Select it seems to be returning an IGrouping, which is what I would expect, only the two data rows in the data object are still ungrouped, even though they are identical. I'm out of google-fu, can anybody please assist?

Answer 1

You could combine the fields to group by into one key (probably a string) and then group by that value:
<!-- language: lang-vb -->
Dim groupedData2 = data.GroupBy(Function(r)
Dim groupKey As New List(Of String)
For Each column In groupByColumns
If column.Value Then
Dim p = r.GetType().GetProperties().FirstOrDefault(Function(p) p.Name = column.Key)
Dim groupingValue = p?.GetValue(r)
groupKey.Add(groupingValue)
End If
Next
Return String.Join(",", groupKey)
End Function)