Gridview中的分页不起作用第二页数据不显示asp.net C＃

Question

Currently I am unable to view page 2 of my gridview upon clicking it. I am not sure why and needed help. I did PageIndexChanging as told, set AllowPaging="True" but still unable to solve this.

Html:

    <asp:GridView ID="SiteGridView" runat="server" CssClass="datagrid" GridLines="Vertical" 
                        AutoGenerateColumns="False" Width="100%" AllowPaging="True" AllowSorting="True" PageSize="10"
                        EnableModelValidation="True" DataKeyNames="promoId"  OnRowCommand="GvPage_RowCommand" 
                        OnPageIndexChanging="GvPage_PageIndexChanging" OnSorting="GvPage_Sorting" onRowdatabound="SiteGridView_RowDataBound">
                        <Columns>                            
                          <asp:TemplateField HeaderText="PromotionId">
                        <ItemTemplate>
                            <asp:Label ID="lblId2" runat="server" Text='<%# Bind("promoId") %>'></asp:Label>
                        </ItemTemplate>
                        <HeaderStyle CssClass="grid_view_hide" />
                        <ItemStyle CssClass="grid_view_hide" />
                    </asp:TemplateField>
                            <asp:TemplateField HeaderText ="Membership Name" SortExpression="name" ItemStyle-Width="50%">
                                <ItemTemplate>
                                    <asp:Label ID="lblSiteName" runat="server" Text='<%# Bind("titlePromo") %>' />
                                </ItemTemplate>
                                <ItemStyle Width="35%" />
                            </asp:TemplateField>
 </Columns>
                    </asp:GridView>

CodeBehind:

  if (!Page.IsPostBack)
            {
                BindData();
                populateDDL();
                ViewState["sortDirection"] = ASCENDING;
                ViewState["sortExpr"] = "titlePromo";
            }

  public void BindData()
        {
            String[,] catNameArr = populateCatID();

            name = (String)Session["titlePromo"];

            categoryName = (String)Session["membershipType"];

            if (categoryName != null)
            {
                DropDownList1.SelectedValue = categoryName;

            }
            else
            {
                Session["titlePromo"] = "";
                Session["membershipType"] = "All";
                categoryName = "All";
                name = "";
                DataSet ds = dal.getEventList();
                DataView myDataView = new DataView(ds.Tables[0]);
                SiteGridView.DataSource = myDataView;
                SiteGridView.DataBind();
                int count = ds.Tables[0].Rows.Count;

                if (count == 0)
                {
                    Label6.Visible = false;
                    Label15.Text = "No record found";
                    Label15.ForeColor = System.Drawing.Color.Gray;
                }
                else if (count == 1)
                {
                    Label6.Visible = true;
                    Label6.Text = count.ToString();
                    Label15.Text = "Total record:";
                    Label15.ForeColor = System.Drawing.Color.Black;
                    successMsg.Visible = false;
                }
                else
                {
                    Label6.Visible = true;
                    Label6.Text = count.ToString();
                    Label15.Text = "Total record:";
                    Label15.ForeColor = System.Drawing.Color.Black;
                    successMsg.Visible = false;
                }

            }
            //if(gridview.row[i].column[1].text/tostring() == ddlcatid.item[j].value.tostring())

            if (name == null)
            {

                    DataSet ds = dal.getPrjMgrList(categoryName);
                    DataView myDataView = new DataView(ds.Tables[0]);
                    SiteGridView.DataSource = myDataView;
                    SiteGridView.DataBind();
                    txtSearch.Text = name;
                    int count = ds.Tables[0].Rows.Count;

                    if (count == 0)
                    {
                        //show no record message
                        Label6.Visible = false;
                        Label15.Text = "No record found";
                        Label15.ForeColor = System.Drawing.Color.Gray;
                        //successMsg.Text = "No records found for this search";
                        //successMsg.Visible = true;
                    }
                    else
                    { //hide no record message
                        if (count == 1)
                        {
                            Label6.Visible = true;
                            Label6.Text = count.ToString();
                            Label15.Text = "Total record:";
                            Label15.ForeColor = System.Drawing.Color.Black;
                            successMsg.Visible = false;
                        }
                        else
                        {
                            Label6.Visible = true;
                            Label6.Text = count.ToString();
                            Label15.Text = "Total records:";
                            Label15.ForeColor = System.Drawing.Color.Black;
                            successMsg.Visible = false;
                        }
                    }

            }
            //changes as of 15/11/2012
            else
            {
                DataSet ds = dal.getPrjMgrList(categoryName, name);
                DataView myDataView = new DataView(ds.Tables[0]);
                SiteGridView.DataSource = myDataView;
                SiteGridView.DataBind();
                int count = ds.Tables[0].Rows.Count;
                txtSearch.Text = name;

                if (count == 0)
                {
                    //show no record message
                    Label6.Visible = false;
                    Label15.Text = "No record found";
                    Label15.ForeColor = System.Drawing.Color.Gray;
                    //successMsg.Text = "No records found for this category";
                    //successMsg.Visible = true;
                }
                else
                { //hide no record message

                    if (count == 1)
                    {
                        Label6.Visible = true;
                        Label6.Text = count.ToString();
                        Label15.Text = "Total record:";
                        Label15.ForeColor = System.Drawing.Color.Black;
                        successMsg.Visible = false;
                    }
                    else
                    {
                        Label6.Visible = true;
                        Label6.Text = count.ToString();
                        Label15.Text = "Total records:";
                        Label15.ForeColor = System.Drawing.Color.Black;
                        successMsg.Visible = false;
                    }
                }
            }

            if (categoryName == "All")
            {
                DataSet ds = dal.getPrjMgrListAll(categoryName, name);
                DataView myDataView = new DataView(ds.Tables[0]);
                SiteGridView.DataSource = myDataView;
                SiteGridView.DataBind();
                int count = ds.Tables[0].Rows.Count;
                txtSearch.Text = name;

                if (count == 0)
                {
                    Label6.Visible = false;
                    Label15.Text = "No record found";
                    Label15.ForeColor = System.Drawing.Color.Gray;
                }
                else if (count == 1)
                {
                    Label6.Visible = true;
                    Label6.Text = count.ToString();
                    Label15.Text = "Total record:";
                    Label15.ForeColor = System.Drawing.Color.Black;
                    successMsg.Visible = false;
                }
                else
                {
                    Label6.Visible = true;
                    Label6.Text = count.ToString();
                    Label15.Text = "Total record:";
                    Label15.ForeColor = System.Drawing.Color.Black;
                    successMsg.Visible = false;
                }


            }


            for (int i = 0; i < SiteGridView.Rows.Count; i++)
            {
                for (int j = 0; j < DropDownList1.Items.Count; j++)
                {
                    if (((Label)SiteGridView.Rows[i].FindControl("lblId2")).Text == DropDownList1.Items[j].Value)
                    {
                        ((Label)SiteGridView.Rows[i].FindControl("lblId2")).Text = DropDownList1.Items[j].Text;
                    }
                }
            }
        }


  protected void GvPage_PageIndexChanging(object sender, GridViewPageEventArgs e)
        {
            SiteGridView.PageIndex = e.NewPageIndex;
            BindData();
        }

Answer 1

First, a suggestion for debugging: temporarily comment out all the complexity. just retrieve a simple dataset with paging enabled. If Paging works as expected then starting adding complexity back in until it fails.

Regarding Paging

In any PageIndexChanging event do not do this:

SiteGridView.PageIndex = e.NewPageIndex;

You are doing manually what the server control does automatically. The value is there so you can check several conditions:

1. Determine if you need to cancel a paging event

    // Is SiteGridView in edit mode \nif( SiteGridView.EditIndex > -1 ) \n    e.Cancel = true;`  

2. Determine if the page is before or after the current page by comparison

    if( SiteGridView.PageIndex > e.NewPageIndex) \n    // Page Down \nelse \n    // Page Up  

3. Or change to some other page because you have some obscure paging algorithim:

    e.NewPageIndex = PageReturnedBySomeObscurePagingAlgorithm();  

Regarding the Page LifeCycle

During a postback, like the one that occurs when you change gridview pages, a Page runs the entire lifecycle on every postback.

So make sure you are not Binding in multiple places or manually setting other gridview control values that may alter paging results. Like setting

`SiteGridView.PageIndex = 1` 

in some event that occurs after the PageIndexChanged event in the LifeCycle.