Linq Group by won't work on multiple columns vb.net

I have a table like this:

PRO_ID     CATEGORY      FINALLY_OK
200          1             55
200          1             60
200          2             65
200          2             80
250          1             55
250          1             60
250          2             65
250          2             80

Here is my code : 

   CType(grdQuality.DataSource, DataView).Table.Rows.Cast(Of DataRow)
   .Select(Function(item) New With {.Ok = CType(item.Item("FINALLY_OK"), Decimal), .PRO_ID = item.Item("PRO_ID"), .Category = item.Item("CATEGORY")})
   .GroupBy(Function(item) New With {.PRO_ID = item.PRO_ID, .Category = item.Category})
   .Select(Function(item) New With {item.Key.PRO_ID, item.Key.Category, .AVG = item.Average(Function(i) i.Ok)})

but this returns all columns again and group by does not work properly

is there anything wrong with my code?

Jon Skeet
people
quotationmark

You're using an anonymous type to group, but you're not making any of those properties key properties... which means they aren't used in the equality tests. Try this:

.GroupBy(Function(item) New With { Key .PRO_ID = item.PRO_ID, Key .Category = item.Category})

(You won't see that in C# samples, as all properties in C# anonymous types are implicitly key properties.)

people

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