VB.NET LINQ Group By Multiple Columns

Question

I have the following LINQ code which has a syntax error and i've no idea how to fix it

         Dim query =
        From row In mainDatatable.AsEnumerable

    'the syntax Error is in the following line
      Group row By new  { row.Field(Of Double)("cprice") , row.Field(Of Integer)("ccategory")} 
Into ProductGroups
    '**************************

                Dim grpNumber = 1
                For Each grp In query
                    For Each row In grp.ProductGroups
                        row.SetField("gnum", grpNumber)
                    Next
                    grpNumber += 1
                Next


            End Sub

so what am i doing wrong?

Here is how the table looks like and i want to group by the columns cprice and ccategory

+---------------+---------------+-----------+------+
| Product Name  | cprice        | ccategory | gnum |
+---------------+---------------+-----------+------+
| Skirt Red     |            99 |         1 |      |
| Jeans Blue    |            49 |         2 |      |
| Jeans Black   |            49 |         2 |      |
| Skirt Blue    |            99 |         1 |      |
| T-shirt White |            20 |         2 |      |
| T-shirt Green |            20 |         2 |      |
| Jeans Grey    |            49 |         2 |      |
+---------------+---------------+-----------+------+

Solution

Try this:

new with { Key.Price = row.Field(Of Double)("cprice") ,
           Key.Category = row.Field(Of Integer)("ccategory")

Uisng the Key modifier, this creates an anonymous type that implements equality based on equality of its members.

Comments

[user1570048]

thanks,the first option worked, but i didn't get the results i expected, i expect the products that have the same cprice and same ccategory to be in a group , so i have 5800 rows it gave me 5800 groups!

[Gert Arnold]

Bit unexpected. Edited my answer.

[Gert Arnold]

For the record: in the mean time I've learned a bit more about equality of anonymous types in VB. See here.

[toddmo]

I could not get this to compile until I added = Group at the end of the statement

[Enigmativity]

To use anonymous types in VB.NET you must use the Key modifier on the individual properties if you want to use them in a group-by\.

[Gert Arnold]

@Enigmativity Thanks for spotting this.