[RESOLVED] LINQ : combine two selects like a SQL CTE?

[geek648]

Ah, brilliant, many thanks!
What a great way to play with data, impressive stuff

The Wrong Way

At first I couldn't get this to work

Dim tst = From row As DataGridViewRow In DataGridView1.Rows

because of an error : Option Strict On disallows implicit conversions from 'Object' to 'System.Windows.Forms.DataGridViewRow'

So to work around that, I toyed with a user-defined variable type (like a Pascal 'record') and a list of those, manually adding to the list from a loop around the DGV.

    Private Structure MyRow
        Property field1 As Double
        Property field2 As Double
    End Structure

        Dim myList As IList(Of MyRow)
        myList = New List(Of MyRow)
        For cnt As Integer = 0 To DataGridView1.Rows.Count - 1
            If Not (DataGridView1.Rows(cnt).IsNewRow) Then
                myList.Add(New myRow() With
                   {.field1 = CDbl(DataGridView1.Rows(cnt).Cells(0).Value),
                    .field2 = CDbl(DataGridView1.Rows(cnt).Cells(1).Value)
                   })
            End If
        Next

        ' LINQ query
        Dim Results = From Rows In myList
                           Group By ... Into ...
                           Select ......
                           Order By .... etc

The Better Way

With a simple Cast, and the help given above, here's the easy way.
Much better now I can do this all in one go!
e.g....

        Dim tst = From row In DataGridView1.Rows.Cast(Of DataGridViewRow)()
                        Where Not row.IsNewRow
                        Select field1 = CDbl(row.Cells(0).Value), field2 = CDbl(row.Cells(1).Value)
                        Group By field1 Into f1_Distinct = Min(field1), f2_Distinct = Max(field2)
                        Select field1 = f1_Distinct, field2 = f2_Distinct
                        Order By field1


        If tst.Count > 0 then MsgBox(tst(0).field1)