if (EditddQuantDesc == null)
{
da = new SqlDataAdapter(selectcommand, con);
dsrow = new DataSet();
da.Fill(dsrow, "QuantityDescriptions");
EditddQuantDesc.DataSource = dsrow.Tables["QuantityDescriptions"];
EditddQuantDesc.DataValueField = dsrow.Tables[0].Columns[0].ToString();
EditddQuantDesc.DataTextField = dsrow.Tables[0].Columns[1].ToString();
}
You check if EditddQuantDesc null and work with it anyway and as the error let's you know, it isn't set to a reference of an object.
Good luck!