ExecuteNonQuery works, DataAdapter doesn't

I am able to Update and Delete using ExecuteNonQuery, but unable to do so using the DataAdapter - strange. Experienced problems when following a Tutorial that used wizards, dataadapter, datagrid, and SQL Server.  But to best diagnose, I transitioned to simple code (first attempt) and added a very simple new table with just 2 fields and no rules or relations in order to rule out dependencies, special database table restriction, or relation problems. The second attempt is the result of debug effort - still short on clues.  

In both attempts the DELETE fails with the DataAdapter/Command Builder but the ExecuteNonQuery works.

first attempt:
private void Page_Load(object sender, System.EventArgs e)
{
        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = "workstation id=JOHN;packet size=4096;" +
                                             "integrated security=SSPI;data source=JOHN;" +
                                             "persist security info=False;initial catalog=Northwind";
        conn.Open();
                  
        string strSQL1 = "SELECT ShipAddressID, ShipAddress FROM dbo.ShipAddress";
        DataSet ds = new DataSet("dsNorthwind");
        SqlDataAdapter da = new SqlDataAdapter(strSQL1, conn);

        // Delete with DataAdapter does not work
        SqlCommandBuilder cb = new SqlCommandBuilder(da);  
        da.Fill(ds, "ShipAddress");
        ds.Tables["ShipAddress"].Rows.RemoveAt(0);
        da.Update(ds, "ShipAddress");

        // Delete with SQL Command works
        string strSQL3 = "DELETE FROM ShipAddress WHERE ShipAddress='Third Address'";
        SqlCommand cmd3 = new SqlCommand(strSQL3, conn);
        int count = cmd3.ExecuteNonQuery();
                  
        conn.Close();
}


second attempt:
private void Page_Load(object sender, System.EventArgs e)
{
    try
    {
        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = "workstation id=JOHN;packet size=4096;" +
                                             "integrated security=SSPI;data source=JOHN;" +
                                             "persist security info=False;initial catalog=Northwind";
        conn.Open();
                  
        string strSQL1 = "SELECT ShipAddressID, ShipAddress " +
                                "FROM dbo.ShipAddress";
        DataSet ds = new DataSet("dsNorthwind");
        SqlDataAdapter da = new SqlDataAdapter(strSQL1, conn);
        da.MissingSchemaAction = MissingSchemaAction.AddWithKey;      // removing doesn't help

        // Delete with DataAdapter does not work
        SqlCommandBuilder cb = new SqlCommandBuilder(da);  
        da.UpdateCommand = cb.GetUpdateCommand();       // removing doesn't help
        da.DeleteCommand = cb.GetDeleteCommand();         // removing doesn't help
        da.Fill(ds, "ShipAddress");
        DataRow dr = ds.Tables["ShipAddress"].Rows[0];
        string ShipAddress1 = (string)dr["ShipAddress"];             // gets 'First Address'
        int numRows1 = ds.Tables["ShipAddress"].Rows.Count;   // equals 4  
        ds.Tables["ShipAddress"].Rows.RemoveAt(0);

        da.Update(ds, "ShipAddress");
        dr = ds.Tables["ShipAddress"].Rows[0];
        string ShipAddress2 = (string)dr["ShipAddress"];           // now gets 'Second Address'  
        int numRows2 = ds.Tables["ShipAddress"].Rows.Count;  // now equals 3

        ds.Tables["ShipAddress"].Reset();
        da.Fill(ds, "ShipAddress");            
        dr = ds.Tables["ShipAddress"].Rows[0];      
        string ShipAddress3 = (string)dr["ShipAddress"];            //  back to 'First Address' since  da.Update  did nothing
        int numRows3 = ds.Tables["ShipAddress"].Rows.Count;   // back to 4

        Response.Write("Count=" + numRows1.ToString() + "/" + numRows2.ToString()+
                                "/" + numRows3.ToString() + " Address=" + ShipAddress1 + "/" +
                                ShipAddress2 + "/" + ShipAddress3);
       // above prints:  "Count=4/3/4 Address=First Address /Second Address /First Address"

        // Delete with SQL Command works
        string strSQL3 = "DELETE FROM ShipAddress WHERE ShipAddress='Third Address'";
        SqlCommand cmd3 = new SqlCommand(strSQL3, conn);
        int count = cmd3.ExecuteNonQuery();
                  
        conn.Close();
    }
    catch (Exception caught)
    {
        Response.Write(caught.ToString());  // does not execute
    }
}

I also tried experimenting with SQL Server to no avail.  Spent a lot of time on this already.  This problem shows up on 2 different computers.  

Thanks for your help.