tableadapter update problem

[arevans]

I can't seem to update the data source when I call the tableadapter's update method. Here is my code:

DealsTableAdapter ta = new DealsTableAdapter();
dsDeals.DealsDataTable dt = new dsDeals.DealsDataTable();
dsDeals.DealsRow dr = dt.NewDealsRow();
dr.NominalRate =varNewRate; // defined above
ta.Update(dr);

The update command on the table adapter looks like this:

UPDATE Deals
SET NominalRate = @NominalRate

If I use the query builder, and supply a parameter value for NominalRate, it works. But otherwise, no.

I am not sure what I am missing here. (I don't want to use sqlCommand as I have many fields to update.
NominalRate is just one of them, just for testing purposes.)

Andy