how to get the lenght of the data field.

What approach are you using? Is it the MaxLength of the field, or is it a specific records length in the field? Do you already have the table loaded into a dataset?

If the last question is answered yes you can do something like this using a typed dataset......

ds.Table.NameColumn.MaxLength, if it is the maxlength you want.

or

ds.Table(index).Name.Length, if it is the length of a specific record.

If this is not tha case, please elaborate.