Webcast: Using Paging

Paging isn't always the easiest thing to figure out - and sometimes not the most performant thing you can do to a we site. Here's a webcast to show you how to set it up both ways: the ASP way, and the SubSonic way.

The code for this web cast is down below...

The HTML:

<table>
    <tr>
        <td>
            <asp:GridView ID="GridView1" runat="server" />

        </td>
    </tr>
    <tr>
        <td>
            <asp:Button ID="btnFirst" runat="server" Text="<< First" CommandArgument="First"  OnClick="pager_Click"/>

            <asp:Button ID="btnPrev" runat="server" Text="< Previous" CommandArgument="Prev"  OnClick="pager_Click"/>

            Page
            <asp:DropDownList ID="ddlPages" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlPages_SelectedIndexChanged">

            </asp:DropDownList> of <asp:Label ID="lblPageCount" runat="server"></asp:Label>

            <asp:Button ID="btnNext" runat="server" Text="Next >" CommandArgument="Next"  OnClick="pager_Click"/>

            <asp:Button ID="btnLast" runat="server" Text="Last >>" CommandArgument="Last"  OnClick="pager_Click"/>

        </td>
    </tr>
</table>

Code Behind

    const int PAGE_SIZE = 10;

    protected void Page_Load(object sender, EventArgs e) {
        if (!Page.IsPostBack) {
            LoadGrid(1);
            SetupPaging();
        }
    }

    void LoadGrid(int pageNumber) {
        Query q = new Query(Northwind.Tables.Product);
        q.PageSize = 10;
        q.PageIndex = pageNumber;
        GridView1.DataSource = q.ExecuteDataSet();
        GridView1.DataBind();

        ResolvePagerView(pageNumber);
    }

    void SetupPaging() {
        int pageCount = 0;
        int totalRecords = 0;
        //check to see if the totals have been set

        if (lblPageCount.Text == string.Empty) {
            totalRecords = new Query(Northwind.Tables.Product).GetCount(Northwind.Product.Columns.ProductID);
        }

        pageCount = totalRecords / PAGE_SIZE;
        if (totalRecords % PAGE_SIZE > 0)
            pageCount++;

        lblPageCount.Text = pageCount.ToString();

        //load up the list items
        for (int i = 1; i <= pageCount; i++) {
            ddlPages.Items.Add(new ListItem(i.ToString(), i.ToString()));
        }

    }
    void ResolvePagerView(int currentPage) {
        int pageCount = 1;

        int.TryParse(lblPageCount.Text, out pageCount);

        int nextPage = currentPage + 1;
        int prevPage = currentPage - 1;

        btnPrev.Enabled = true;
        btnNext.Enabled = true;
        btnLast.Enabled = true;
        btnFirst.Enabled = true;

        if (currentPage == pageCount) {
            btnNext.Enabled = false;
            btnLast.Enabled = false;
        } else if (currentPage == 1) {
            btnPrev.Enabled = false;
            btnFirst.Enabled = false;
        }

    }
    protected void pager_Click(object sender, EventArgs e) {
        Button btn = (Button)sender;
        string pageCommand = btn.CommandArgument;
        int currentPage = ddlPages.SelectedIndex + 1;

        switch (pageCommand) {
            case "First":
                currentPage = 1;
                break;
            case "Prev":
                currentPage--;
                break;
            case "Next":
                currentPage++;
                break;
            case "Last":
                currentPage = int.Parse(lblPageCount.Text);
                break;
        }

        //reset the DropDown

        ddlPages.SelectedValue = currentPage.ToString();

        //reload the grid
        LoadGrid(currentPage);

    }
    protected void ddlPages_SelectedIndexChanged(object sender, EventArgs e) {
        //reload the grid
        LoadGrid(ddlPages.SelectedIndex + 1);

    }