c#大圣之路笔记——c# 从DataGrid中导出数据 Session

///前端代码
<tr>
            <td align="right">
                <asp:Button ID="btnExport" runat="server" Text="导出错误数据" CssClass="fieldButton" OnClick="btnExport_Click"   style="  height:24px; 100px"></asp:Button>
            </td>
        </tr>

///前端代码
 <tr>
            <td colspan="4"> 
             <asp:DataGrid ID="GridMain" runat="server" Width="100%" AutoGenerateColumns="False"
                 AllowPaging="True" PageSize="20" AllowSorting="True" DataMember="" OnPageIndexChanged="GridMain_PageIndexChanged"
                  AlternatingItemStyle-BackColor="#EBE9E9">
                  <AlternatingItemStyle CssClass="datagridAlternating" ></AlternatingItemStyle>
                  <HeaderStyle CssClass="tableHead" Height="22" ></HeaderStyle>
                  <Columns>
                        <asp:BoundColumn DataField="errorMessage" HeaderText="错误原因">
                            <ItemStyle HorizontalAlign="Center" Width="8%" ></ItemStyle>
                        </asp:BoundColumn>
                         <asp:BoundColumn DataField="GID" HeaderText="GID">
                            <ItemStyle HorizontalAlign="Center" Width="4%" ></ItemStyle>
                        </asp:BoundColumn>
                         
                  </Columns>
                   <PagerStyle Position="Top" Mode="NumericPages"></PagerStyle>
              </asp:DataGrid>
          
            </td>
         </tr>

//后台代码
   private DataTable Err_dt;
   private string tableName;

    //通过把table中的值放在 Session中，绑定到datagrid中
    Session[tableName] = Err_dt;

private void bindNextPage(int p)
        {
            tableName = ViewState["TableName"].ToString();
            Err_dt = (DataTable)Session[tableName];
            if (ViewState["Sort"].ToString() != "")
            {
                DataView dv = new DataView(Err_dt);
                dv.Sort = ViewState["Sort"].ToString();
                GridMain.DataSource = dv;
            }
            else
            {
                GridMain.DataSource = Err_dt;
            }

            GridMain.CurrentPageIndex = p;
            GridMain.DataBind();
            return;
        } 

    protected void btnExport_Click(object sender, EventArgs e)
        {
            GridMain.AllowPaging = false;
            GridMain.AllowSorting = false;
             
            bindNextPage(0);

            Export(GridMain, "ChannelStoreErrorList.xls", "ChannelStoreErrorList", "application/ms-excel");

            GridMain.AllowPaging = true;
            GridMain.AllowSorting = false;
        }
        protected void GridMain_PageIndexChanged(object source, System.Web.UI.WebControls.DataGridPageChangedEventArgs e)
        { 
            currentPageIndex = e.NewPageIndex;
            this.GridMain.CurrentPageIndex = currentPageIndex;
            //DataTable Err_dt = new DataTable();
            //Err_dt = BindERData();
            GridMain.DataSource = Err_dt;
            GridMain.DataBind();
        }


        #region  Export to the excel


        // Export to the excel
        private void Export(System.Web.UI.WebControls.DataGrid dg, string fileName, string fn, string typeName)
        {
            System.Web.HttpResponse httpResponse = Page.Response;
            httpResponse.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
            httpResponse.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
            httpResponse.ContentType = typeName;
            System.IO.StringWriter tw = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter(tw);
            dg.RenderControl(hw);

            //httpResponse.Write(tw.ToString());
            //httpResponse.End();
            string filePath = Server.MapPath("..") + fn + DateTime.Now.Ticks.ToString() + new Random().Next(100).ToString();
            System.IO.StreamWriter sw = System.IO.File.CreateText(filePath);
            sw.Write(tw.ToString());
            sw.Close();
            DownFile(httpResponse, fileName, filePath);

            httpResponse.End();
        }

        private bool DownFile(System.Web.HttpResponse Response, string fileName, string fullPath)
        {
            try
            {
                Response.ContentType = "application/octet-stream";

                Response.AppendHeader("Content-Disposition", "attachment;filename=" +
                HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8) + ";charset=GB2312");
                System.IO.FileStream fs = System.IO.File.OpenRead(fullPath);
                long fLen = fs.Length;
                int size = 102400;//每100K同时下载数据
                byte[] readData = new byte[size];//指定缓冲区的大小
                if (size > fLen) size = Convert.ToInt32(fLen);
                long fPos = 0;
                bool isEnd = false;
                while (!isEnd)
                {
                    if ((fPos + size) > fLen)
                    {
                        size = Convert.ToInt32(fLen - fPos);
                        readData = new byte[size];
                        isEnd = true;
                    }
                    fs.Read(readData, 0, size);//读入一个压缩块
                    Response.BinaryWrite(readData);
                    fPos += size;
                }
                fs.Close();
                FileInfo FI = new FileInfo(fullPath);
                if (FI.Exists)
                {
                    FI.Delete();
                }
                return true;
            }
            catch
            {
                return false;
            }
        }

        #endregion