复制DataRow,小技巧

        /// <summary>
        /// 包装单位选择发生变化
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void ddlUnitname_SelectedIndexChanged(object sender, EventArgs e)
        {
            //选择不同的包装入库
            DataSet ds = (DataSet)ViewState["dbMateriels"];
            DataTable tmp1dt = ds.Tables[0];
            DataTable tardt = tmp1dt.Clone();
            for (int i = 0; i < tmp1dt.Rows.Count; i++)
            {
                for (int j = 0; j < gvMaterialDetail.Rows.Count; j++)
                {
                    if (tmp1dt.Rows[i]["tmpid"].ToString() == gvMaterialDetail.DataKeys[j]["tmpid"].ToString())
                    {
                        DropDownList ddl = (DropDownList)gvMaterialDetail.Rows[j].FindControl("ddlUnitname");
                        Label lbl = (Label)gvMaterialDetail.Rows[j].FindControl("lblUnitname");
                        DataRow dr = tardt.NewRow();
                        dr = tmp1dt.Rows[i];
                        if (ddl.SelectedValue.ToString() != null && ddl.SelectedValue.ToString() != "")
                        {
                            dr["unit"] = ddl.SelectedValue.ToString();
                        }
                        tardt.Rows.Add(dr.ItemArray);
                    }
                }
            }
            gvMaterialDetail.DataSource = tardt;
            this.gvMaterialDetail.DataKeyNames = new string[] { "unit", "recordid", "tmpid","billleftnumb","numb" };
            gvMaterialDetail.DataBind();
        }

　　　　　　　　DataRow dr = tardt.NewRow();
                        dr = tmp1dt.Rows[i];
                        if (ddl.SelectedValue.ToString() != null && ddl.SelectedValue.ToString() != "")
                        {
                            dr["unit"] = ddl.SelectedValue.ToString();
                        }

                        tardt.Rows.Add(dr.ItemArray);

如果tardt.Rows.Add(dr)

就会产生该列已属于另一个表的错误