Finding null value in Dataset - DataRow.IsNull method vs ==DbNull.Value - c#

Question

What are the benefits of using the c# method DataRow.IsNull to determine a null value over checking if the row equals DbNull.value?

if(ds.Tables[0].Rows[0].I         


        

Answer 1

FWIW, I wrote a bunch of DataRow extension methods — CastAsXXX() — to avoid having to deal with DB nullability...or at least defer it a bit B^). Here's my CastAsInt() and CastAsIntNullable() methods:

#region downcast to int

public static int CastAsInt( this DataRow row , int index )
{
  return toInt( row[index] ) ;
}
public static int CastAsInt( this DataRow row , string columnName )
{
  return toInt( row[columnName] ) ;
}

public static int? CastAsIntNullable( this DataRow row , int index )
{
  return toIntNullable( row[index] );
}
public static int? CastAsIntNullable( this DataRow row , string columnName )
{
  return toIntNullable( row[columnName] ) ;
}

#region conversion helpers

private static int toInt( object o )
{
  int value = (int)o;
  return value;
}

private static int? toIntNullable( object o )
{
  bool hasValue = !( o is DBNull );
  int? value    = ( hasValue ? (int?) o : (int?) null ) ;
  return value;
}

#endregion conversion helpers

#endregion downcast to int

Usage is pretty straightforward. You just need to state your expectations up front.

DataRow dr = GetADataRowFromSomewhere() ;
// Throws NullReferenceException if the column is null
int     x  = dr.CastAsInt(         "column_1" ) ;
// Is perfectly happy with nulls (as it should be)
int?    y  = dr.CastAsIntNullable( "column_1" ) ;

I tried to make them generic, but no dice unless I'm willing to correlate NULLs from the database with the default value for the type (e.g., 0 for numeric types), which I'm not.