ado.net dataset unique constraint does not prevent adding/merging rows which violate unique constraint

The problem is that Adding in new rows (with DataSet.Fill) that have duplicates will allow those duplicates to be added in spite of the constraint, then after the rows are added, then throws an exception.  Thus, if you want to add rows that may violate any constraints, this must be done manually, checking that constraints will be satisfied (by searching columns via index) and only then adding the row, otherwise throw an exception.  One may want to validate that all rows can be added successfully before adding in new rows.

To say the least, this is not satisfying, intuitive behavior from Microsoft...

Thanks for the responses.  As I stated before, it is strange that Fill will populate rows in violation of a unique constraint, then throw an exception.