string sql="";

dbhelper.ExecuteNonQuery(sql);

DataTable dt = dbhelper.GetDataTable(sql);

if (dt != null && dt.Rows.Count > 0)

{

    SqlBulkCopy bcp = new SqlBulkCopy("server=.;database=Service;uid=sa;pwd=123456");

    bcp.DestinationTableName = "InventoryDiff";

    bcp.WriteToServer(dt);

}