Asp.net delete data from dataset and database in disconnected mode

 protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        string ph = ds.Tables[0].Rows[e.RowIndex][0].ToString();
        adpt = new SqlDataAdapter();
        comm = new SqlCommand();
        comm.CommandText = "delete from Categories where CategoryID = " + ph;
        comm.CommandType = CommandType.Text;
        comm.Connection = con;
       
        adpt.DeleteCommand = comm;
       
        adpt.Update(ds);

        select();

        GridView1.DataSource = ds;
        GridView1.EditIndex = -1;
        GridView1.DataBind();
    }

this code is supposed to delete a record in dataset and then delete it from database using the gridview, it doesn't generate any errors but it doesn't delete the record from the dataset