Suppose that there is a DataTable dt of type double with the columns "x","y","z" in C#.
While values are filled into dt, it certainly occurs that only two dimensions are assigned a being assigned which intentionally leaves the third vacant with DBNull.Value.
When computing the average for a dimension with a filter according to Transact-SQL syntax things work properly:
X = (double)dt.Compute("Avg([x])", "x IS NOT NULL");
However, the following results in System.InvalidCastException: 'Specified cast is not valid.'
sx = (double)dt.Compute("StDev([x])", "x IS NOT NULL");
This would be highly convenient compared to a seperate method to calculate the standard deviation . And even at this point there is trouble when converting a column with null values into a List:
List<double> xValues = dt.Rows.OfType<DataRow>().Select(dr => dt.Field<double>("x")).ToList();
System.InvalidCastException: 'Cannot cast DBNull.Value to type 'System.Double'. Please use a nullable type.'
Any suggestions on handling this situation be it with null-conditionals or suggestions on the filter are highly appreciated.