Data column length probem

I'm retrieving a data column from SQL Server 2000 which has the type Varchar
with length set to 10. The MaxLength method of DataColumn object returns -1
instead of the correct size which is 10. Does anybody have an idea why C#
doesn't read the correct length?
Here is the code

foreach (DataColumn _dataColumn in importDataSet.Tables[0].Columns)

{

if (_dataColumn.MaxLength < _rawFieldValue.ToString().Length)

}


Thanks,
Gilgamesh