C# Datatable: Computing the average in a column

Question

I'm trying to get the average P&L in a column. The column is of type double, however I keep getting an error saying the following:

Additional information: Syntax error in aggregate argument: Expecting a single column argument with possible 'Child' qualifier.

This occurs when this line is executing:

avgFiveSbefore = (double)dt.Compute("AVG(5sBeforePnL)", "");

Also, here's some additional code to clarify:

dt.Columns.Add(Columns.FiveSecBeforePnL, typeof(double));

foreach(DataRow row in dt.Rows)
{
  row[Columns.FiveSecBeforePnL] = some value;
}

double avgFiveSbefore;
avgFiveSbefore = (double)dt.Compute("AVG(5sBeforePnL)", "");

Could you try changing the column name to something that doesn't start with a number? Just thinking that might be the cause. — John Yost
– John Yost, Commented Feb 25, 2014 at 18:49

Habib · Accepted Answer · 2014-02-25 18:47:22Z

9

Try enclosing the column name in square brackets.

avgFiveSbefore = (double)dt.Compute("AVG([5sBeforePnL])", "");

You can also use LINQ to do the same like:

double avgFiveSbefore = dt.AsEnumerable()
                            .Average(r =>
                                r.Field<double>(Columns.FiveSecBeforePnL));

answered Feb 25, 2014 at 18:47

Habib

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