Hi lisamaclea,

Using the below article i have created the example.

Implement Paging in DataList control in ASP.Net

Check this example. Now please take its reference and correct your code.

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

HTML

C#

<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false" DataKeyNames="CustomerID">
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:ImageButton ID="imgShow" runat="server" OnClick="Show_Hide_ChildGrid" ImageUrl="~/Images/plus.png"
                    CommandArgument="Show" />
                <asp:Panel ID="pnlOrders" runat="server" Visible="false" Style="position: relative">
                    <asp:GridView ID="gvOrders" runat="server" AutoGenerateColumns="false" PageSize="5"
                        AllowPaging="true" OnPageIndexChanging="OnChildGrid_PageIndexChanging">
                        <Columns>
                            <asp:BoundField DataField="OrderId" HeaderText="Order Id" />
                            <asp:BoundField DataField="OrderDate" HeaderText="Date" />
                        </Columns>
                    </asp:GridView>
                </asp:Panel>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="ContactName" HeaderText="Name" />
        <asp:BoundField DataField="City" HeaderText="City" />
        <asp:BoundField DataField="Country" HeaderText="Country" />
    </Columns>
</asp:GridView>
<div style="margin: 5px">
    <asp:Repeater ID="rptPager" runat="server">
        <ItemTemplate>
            <asp:LinkButton ID="lnkPage" runat="server" Text='<%#Eval("Text") %>' CommandArgument='<%# Eval("Value") %>'
                CssClass='<%# Convert.ToBoolean(Eval("Enabled")) ? "page_enabled" : "page_disabled" %>'
                Enabled='<%# Eval("Enabled") %>' OnClick="Page_Changed"></asp:LinkButton>
        </ItemTemplate>
    </asp:Repeater>
</div>

VB.Net

<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false" DataKeyNames="CustomerID">
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:ImageButton ID="imgShow" runat="server" OnClick="Show_Hide_ChildGrid" ImageUrl="~/Images/plus.png"
                    CommandArgument="Show" />
                <asp:Panel ID="pnlOrders" runat="server" Visible="false" Style="position: relative">
                    <asp:GridView ID="gvOrders" runat="server" AutoGenerateColumns="false" PageSize="5"
                        AllowPaging="true" OnPageIndexChanging="OnChildGrid_PageIndexChanging">
                        <Columns>
                            <asp:BoundField DataField="OrderId" HeaderText="Order Id" />
                            <asp:BoundField DataField="OrderDate" HeaderText="Date" />
                        </Columns>
                    </asp:GridView>
                </asp:Panel>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="ContactName" HeaderText="Name" />
        <asp:BoundField DataField="City" HeaderText="City" />
        <asp:BoundField DataField="Country" HeaderText="Country" />
    </Columns>
</asp:GridView>
<div style="margin: 5px">
    <asp:Repeater ID="rptPager" runat="server">
        <ItemTemplate>
            <asp:LinkButton ID="lnkPage" runat="server" Text='<%#Eval("Text") %>' CommandArgument='<%# Eval("Value") %>'
                CssClass='<%# If(Convert.ToBoolean(Eval("Enabled")), "page_enabled", "page_disabled")%>'
                Enabled='<%# Eval("Enabled") %>' OnClick="Page_Changed"></asp:LinkButton>
        </ItemTemplate>
    </asp:Repeater>
</div>

JavaScript and CSS

<style type="text/css">
    body
    {
        font-family: Arial;
        font-size: 10pt;
    }
    table
    {
        border: 1px solid #ccc;
    }
    table th
    {
        background-color: #F7F7F7;
        color: #333;
        font-weight: bold;
    }
    table th, table td
    {
        padding: 5px;
        border-color: #ccc;
    }
    .page_enabled, .page_disabled
    {
        display: inline-block;
        height: 25px;
        min-width: 30px;
        line-height: 25px;
        text-align: center;
        text-decoration: none;
        border: 1px solid #ccc;
    }
    .page_enabled
    {
        background-color: #eee;
        color: #000;
    }
    .page_disabled
    {
        background-color: #6C6C6C;
        color: #fff !important;
    }
</style>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () {
        $("[src*=minus]").each(function () {
            $(this).closest("tr").after("<tr><td></td><td colspan = '999'>" + $(this).next().html() + "</td></tr>");
            $(this).next().remove()
        });
    });
</script>

Namespaces

C#

using System.Configuration;
using System.Data;
using System.Data.SqlClient;

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient

Code

C#

private int PageSize = 10;
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        this.GetCustomersPageWise(1);
    }
}

protected void Show_Hide_ChildGrid(object sender, EventArgs e)
{
    ImageButton imgShowHide = (sender as ImageButton);
    GridViewRow row = (imgShowHide.NamingContainer as GridViewRow);
    if (imgShowHide.CommandArgument == "Show")
    {
        row.FindControl("pnlOrders").Visible = true;
        imgShowHide.CommandArgument = "Hide";
        imgShowHide.ImageUrl = "~/Images/minus.png";
        string customerId = gvCustomers.DataKeys[row.RowIndex].Value.ToString();
        GridView gvOrders = row.FindControl("gvOrders") as GridView;
        BindOrders(customerId, gvOrders);
    }
    else
    {
        row.FindControl("pnlOrders").Visible = false;
        imgShowHide.CommandArgument = "Show";
        imgShowHide.ImageUrl = "~/Images/plus.png";
    }
}

protected void OnChildGrid_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    GridView gvOrders = (sender as GridView);
    gvOrders.PageIndex = e.NewPageIndex;
    BindOrders(gvOrders.ToolTip, gvOrders);
}

protected void Page_Changed(object sender, EventArgs e)
{
    int pageIndex = int.Parse((sender as LinkButton).CommandArgument);
    this.GetCustomersPageWise(pageIndex);
}

private void GetCustomersPageWise(int pageIndex)
{
    string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        using (SqlCommand cmd = new SqlCommand("Customers_GetCustomersWithPaging", con))
        {
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@PageIndex", pageIndex);
            cmd.Parameters.AddWithValue("@PageSize", PageSize);
            cmd.Parameters.Add("@RecordCount", SqlDbType.Int, 4);
            cmd.Parameters["@RecordCount"].Direction = ParameterDirection.Output;
            con.Open();
            IDataReader idr = cmd.ExecuteReader();
            gvCustomers.DataSource = idr;
            gvCustomers.DataBind();
            idr.Close();
            con.Close();
            int recordCount = Convert.ToInt32(cmd.Parameters["@RecordCount"].Value);
            this.PopulatePager(recordCount, pageIndex);
        }
    }
}

private void BindOrders(string customerId, GridView gvOrders)
{
    gvOrders.ToolTip = customerId;
    gvOrders.DataSource = GetData(string.Format("SELECT * FROM Orders WHERE CustomerID='{0}'", customerId));
    gvOrders.DataBind();
}

private DataTable GetData(string query)
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand())
        {
            cmd.CommandText = query;
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataSet ds = new DataSet())
                {
                    DataTable dt = new DataTable();
                    sda.Fill(dt);
                    return dt;
                }
            }
        }
    }
}

private void PopulatePager(int recordCount, int currentPage)
{
    List<ListItem> pages = new List<ListItem>();
    int startIndex, endIndex;
    int pagerSpan = 5;

    //Calculate the Start and End Index of pages to be displayed.
    double dblPageCount = (double)((decimal)recordCount / Convert.ToDecimal(PageSize));
    int pageCount = (int)Math.Ceiling(dblPageCount);
    startIndex = currentPage > 1 && currentPage + pagerSpan - 1 < pagerSpan ? currentPage : 1;
    endIndex = pageCount > pagerSpan ? pagerSpan : pageCount;
    if (currentPage > pagerSpan % 2)
    {
        if (currentPage == 2)
        {
            endIndex = 5;
        }
        else
        {
            endIndex = currentPage + 2;
        }
    }
    else
    {
        endIndex = (pagerSpan - currentPage) + 1;
    }

    if (endIndex - (pagerSpan - 1) > startIndex)
    {
        startIndex = endIndex - (pagerSpan - 1);
    }

    if (endIndex > pageCount)
    {
        endIndex = pageCount;
        startIndex = ((endIndex - pagerSpan) + 1) > 0 ? (endIndex - pagerSpan) + 1 : 1;
    }

    //Add the First Page Button.
    if (currentPage > 1)
    {
        pages.Add(new ListItem("First", "1"));
    }

    //Add the Previous Button.
    if (currentPage > 1)
    {
        pages.Add(new ListItem("Previous", (currentPage - 1).ToString()));
    }

    for (int i = startIndex; i <= endIndex; i++)
    {
        pages.Add(new ListItem(i.ToString(), i.ToString(), i != currentPage));
    }

    //Add the Next Button.
    if (currentPage < pageCount)
    {
        pages.Add(new ListItem("Next", (currentPage + 1).ToString()));
    }

    //Add the Last Button.
    if (currentPage != pageCount)
    {
        pages.Add(new ListItem("Last", pageCount.ToString()));
    }
    rptPager.DataSource = pages;
    rptPager.DataBind();
}

VB.Net

Private PageSize As Integer = 10
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not IsPostBack Then
        Me.GetCustomersPageWise(1)
    End If
End Sub

Protected Sub Show_Hide_ChildGrid(ByVal sender As Object, ByVal e As EventArgs)
    Dim imgShowHide As ImageButton = (TryCast(sender, ImageButton))
    Dim row As GridViewRow = (TryCast(imgShowHide.NamingContainer, GridViewRow))
    If imgShowHide.CommandArgument = "Show" Then
        row.FindControl("pnlOrders").Visible = True
        imgShowHide.CommandArgument = "Hide"
        imgShowHide.ImageUrl = "~/Images/minus.png"
        Dim customerId As String = gvCustomers.DataKeys(row.RowIndex).Value.ToString()
        Dim gvOrders As GridView = TryCast(row.FindControl("gvOrders"), GridView)
        BindOrders(customerId, gvOrders)
    Else
        row.FindControl("pnlOrders").Visible = False
        imgShowHide.CommandArgument = "Show"
        imgShowHide.ImageUrl = "~/Images/plus.png"
    End If
End Sub

Protected Sub OnChildGrid_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)
    Dim gvOrders As GridView = (TryCast(sender, GridView))
    gvOrders.PageIndex = e.NewPageIndex
    BindOrders(gvOrders.ToolTip, gvOrders)
End Sub

Protected Sub Page_Changed(ByVal sender As Object, ByVal e As EventArgs)
    Dim pageIndex As Integer = Integer.Parse((TryCast(sender, LinkButton)).CommandArgument)
    Me.GetCustomersPageWise(pageIndex)
End Sub

Private Sub GetCustomersPageWise(ByVal pageIndex As Integer)
    Dim constring As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constring)
        Using cmd As SqlCommand = New SqlCommand("Customers_GetCustomersWithPaging", con)
            cmd.CommandType = CommandType.StoredProcedure
            cmd.Parameters.AddWithValue("@PageIndex", pageIndex)
            cmd.Parameters.AddWithValue("@PageSize", PageSize)
            cmd.Parameters.Add("@RecordCount", SqlDbType.Int, 4)
            cmd.Parameters("@RecordCount").Direction = ParameterDirection.Output
            con.Open()
            Dim idr As IDataReader = cmd.ExecuteReader()
            gvCustomers.DataSource = idr
            gvCustomers.DataBind()
            idr.Close()
            con.Close()
            Dim recordCount As Integer = Convert.ToInt32(cmd.Parameters("@RecordCount").Value)
            Me.PopulatePager(recordCount, pageIndex)
        End Using
    End Using
End Sub

Private Sub BindOrders(ByVal customerId As String, ByVal gvOrders As GridView)
    gvOrders.ToolTip = customerId
    gvOrders.DataSource = GetData(String.Format("SELECT * FROM Orders WHERE CustomerID='{0}'", customerId))
    gvOrders.DataBind()
End Sub

Private Function GetData(ByVal query As String) As DataTable
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Using cmd As SqlCommand = New SqlCommand()
            cmd.CommandText = query
            Using sda As SqlDataAdapter = New SqlDataAdapter()
                cmd.Connection = con
                sda.SelectCommand = cmd
                Using ds As DataSet = New DataSet()
                    Dim dt As DataTable = New DataTable()
                    sda.Fill(dt)
                    Return dt
                End Using
            End Using
        End Using
    End Using
End Function

Private Sub PopulatePager(ByVal recordCount As Integer, ByVal currentPage As Integer)
    Dim pages As List(Of ListItem) = New List(Of ListItem)()
    Dim startIndex, endIndex As Integer
    Dim pagerSpan As Integer = 5
    Dim dblPageCount As Double = CDbl((CDec(recordCount) / Convert.ToDecimal(PageSize)))
    Dim pageCount As Integer = CInt(Math.Ceiling(dblPageCount))
    startIndex = If(currentPage > 1 AndAlso currentPage + pagerSpan - 1 < pagerSpan, currentPage, 1)
    endIndex = If(pageCount > pagerSpan, pagerSpan, pageCount)
    If currentPage > pagerSpan Mod 2 Then
        If currentPage = 2 Then
            endIndex = 5
        Else
            endIndex = currentPage + 2
        End If
    Else
        endIndex = (pagerSpan - currentPage) + 1
    End If

    If endIndex - (pagerSpan - 1) > startIndex Then
        startIndex = endIndex - (pagerSpan - 1)
    End If

    If endIndex > pageCount Then
        endIndex = pageCount
        startIndex = If(((endIndex - pagerSpan) + 1) > 0, (endIndex - pagerSpan) + 1, 1)
    End If

    If currentPage > 1 Then
        pages.Add(New ListItem("First", "1"))
    End If

    If currentPage > 1 Then
        pages.Add(New ListItem("Previous", (currentPage - 1).ToString()))
    End If

    For i As Integer = startIndex To endIndex
        pages.Add(New ListItem(i.ToString(), i.ToString(), i <> currentPage))
    Next

    If currentPage < pageCount Then
        pages.Add(New ListItem("Next", (currentPage + 1).ToString()))
    End If

    If currentPage <> pageCount Then
        pages.Add(New ListItem("Last", pageCount.ToString()))
    End If

    rptPager.DataSource = pages
    rptPager.DataBind()
End Sub

Screenshot