C# DataTable LINQ & GROUP BY

Question

I have a DataTable with 20 columns (I only need 3 of them.) I need to perform the following query on it and then save the results as an array. I've done some searching, but I can't figure out how to perform the mathematical operation. I know LINQ should be used, but I'm not getting anywhere. Any help is greatly appreciated!

SELECT DISTINCT columnZ, (columnX + columnY) / 2 FROM DataTable

*EDIT - corrected SQL statement

How's that meant to work? When you group by columnZ, your select clause can not include non-aggregating function depending on columns other than columnZ itself. Can you explain us the broader problem you are trying to solve? — Dmitry Ornatsky
– Dmitry Ornatsky, Commented Nov 6, 2010 at 17:30
Group-by is an aggregating function; you would need to take something like a sum,min,max etc for that to make sense. — Marc Gravell
– Marc Gravell, Commented Nov 6, 2010 at 17:30
Okay, how about this: SELECT DISTINCT columnZ, (columnX + columnY) / 2 FROM DataTable I only want to send the second column to an array — bgeveritt
– bgeveritt, Commented Nov 6, 2010 at 17:34

Dmitry Ornatsky · Accepted Answer · 2010-11-06 18:12:47Z

3

Answering your last comment (I suggest you update the question):

  var result = 
    (from row in dataTable.AsEnumerable()
     let average = ((double)row["columnX"] + (double)row["columnY"])/2
     select new 
     {
        ColumnZ = (string)row["columnZ"],
        Average = average
     }).Distinct();

Use your actual data types.

edited Nov 6, 2010 at 18:12

answered Nov 6, 2010 at 17:40

Dmitry Ornatsky

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