Ross Coded Classes

September 1, 2009

DataRow.IsNull(column) is preferred over testing for DBNull.Value

Filed under: .NET Tips — Tags: , — Ross Bradbury @ 12:27 pm

Please try to use the IsNull method on DataRow to determine if a value is null or not. DataRow/DataColumn does not actually store null or DBNull – it has a BitArray that says whether or not a non-null value is stored in which columns in the row.  Retrieving the column’s value for the row creates a copy of the DBNull.Value structure which doesn’t get created when calling the IsNull method.  Ideally this performance difference is never observable, but I feel it does tend to make the code cleaner and is the more correct implementation.

// This is better than any of the many possible 
// variations of checking the value


// discouraged


myDataRow[someColumnName] == DBNull.Value

myDataRow[someColumnName] is DBNull

!(myDataRow[someColumnName] is Int32) // (or appropriate type)

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