Problems with merging two datasets!

[Kjetil]

Hi!
I've got a WebService supplying me with a dataset:

Webservice:
DataSet ds = new DataSet();
OdbcDataAdapter adapter = new OdbcDataAdapter(select,connect);
adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
adapter.Fill(ds, "Table1");

When I instantiate my program I retrieve a dataset(ds1) from my
webservice.

Further I poll the webservice occationally to receive the same type of
dataset(ds2).
I merge the two datasets:

DataColumn[] dcc = new DataColumn[1];
dcc[0] = currentDb.Tables["Table1"].Columns["id"];
currentDb.Tables["Table1"].PrimaryKey = dcc;
this.db.Merge(currentDb, true);

if(db.HasChanges(DataRowState.Modified | DataRowState.Added))
{
//do something..
}

Now, to the problem: When I merge the two datasets I get the
DataRowState to be modified even if the datasets that are merged are
identical. It looks that the source dataset is overwriting the target
dataset, which I would not like it to do!
How can I keep the target dataset as it is when there is no update in
the source dataset?

Thanks in advance!

Kjetil