Peder,  in response to your question about "do i need to retrieve all
the rows", I believe there are at least 2 and maybe 3 ways to do it.
You should be able to build everything by hand. If you want to build it
by hand then a dataconnectionis not required to retrieve the columns
because you will add them manually via code.
If you want the columns to be added automatically you need to select at
least one row. There might be a way to read the schema from a table and
use this for a dataset. I have not seen a method of doing this so I
can't comment on whehter itis possible.

What I DO do is i do a =
bwcLogic.NewSproc("SecretOperation_PerformedOperations_ListNone"); This
is a stored procedure that basically queries the table but retrieves no
rows. Once again, this may not be the best solution, but sometimes in
the absence of more real-world practical documentation/samples we make
do with what makes sense to us.

In response to your Question about updating. This is what I do .

OleDA.InsertCommand                    =
bwcLogic.NewSproc("Dental_PerformedOperations_Insert",
    new SqlParameter("@SSN",    SqlDbType.VarChar,    50,        "SSN"),
    new SqlParameter("@Code",    SqlDbType.VarChar,    5,        "Code"),
    new SqlParameter("@Note",    SqlDbType.VarChar,    255,    "Note"),
    new SqlParameter("@Times",    SqlDbType.Int,        4,        "Times")
// Here I am using a Stored Procedure, for increased performance and
security reasons. The 4th most parameter maps the column name to the
parameter. For each row that is inserted it will execute this command
mapping as I have specified. This is why it is possible to build the
table manually with code adding the columns yourself. You just need to
make sure the data type and sizes are the appropriate data type.
// code goes here to insert all your rows
then simply go
OleDA.Update(TmpDS, TableName);
// close connections and cleanup.

Please note, that the actual order is not significant however.

Hope this helps to answer some of your questions.