Find index value of repeater to open new webform and read data from SQL

Question

How do I pass the ID value linked to a repeater row to open the values in a new webform with textfields which can then be edited and updated in repeater (SQL Stored procedure). I am new to repeaters and I managed to do this using a GridView but I'm not sure how to do it with a repeater.

What I did with the GridView c# which worked perfect in Default.aspx.cs:

if (dgvEmployees.SelectedIndex != -1)
{
    indexId = dgvEmployees.SelectedRow.Cells[1].Text;
    Response.Redirect("About.aspx?&Id=" + indexId);
}

What is received in About.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
    if(!String.IsNullOrEmpty(Request.QueryString["Id"]))
    {
       idNum = Convert.ToInt32(Request.QueryString["Id"]);
       if(!IsPostBack)
       {
           FillEmployeeData();
       }
     }
 }

This is the repeater code:

<asp:Repeater ID="rptList" runat="server" OnItemDataBound="rptList_ItemDataBound" Visible="true">
            <HeaderTemplate>

                <table class="table table-bordered" id="VersionsTable">
                    <tr>
                        <th>Actions
                        </th>
                        <th>Employee Number
                        </th>
                         <th>ID Number
                        </th>
                         <th>Employee Name
                        </th>
                         <th>Employee Surname
                        </th>
                         <th>Number of Dependants
                        </th>
                         <th>Race
                        </th>
                        <th>Gender
                        </th>
                        <th>Delete
                        </th>
                    </tr>
            </HeaderTemplate>
            <ItemTemplate>
                <tbody>
                    <tr style="cursor:pointer" onmouseover="style.backgroundColor='#E6E6E6'" onmouseout="style.backgroundColor=''" onclick="style.backgroundColor='#727A91'">
                        <asp:HiddenField ID="hIDfield" runat="server" Value='<%#Eval("Id")%>' />
                        <td>
                            <asp:button runat="server" OnClick="btnEdit_Click" CssClass="btn btn-default" Text="Edit"/> 

                        </td>
                        <td onclick="PopupEdit('<%# Eval("EmployeeNumber") %>')">
                            <%# Eval("EmployeeNumber") %>
                        </td>
                        <td>
                            <%# Eval("IDNumber") %>
                        </td>
                        <td>
                            <%# Eval("employeeName") %>
                        </td>
                        <td>
                            <%# Eval("employeeSurname") %>
                        </td>
                        <td>
                            <%# Eval("numberOfDependants") %>
                        </td>
                        <td>
                            <%# Eval("RaceId") %>
                        </td>
                        <td>
                            <%# Eval("GenderId") %>
                        </td>
                        <td style="text-align:center">
                            <asp:CheckBox ID="chkDelete" CssClass="form-control" runat="server" />
                        </td>
                    </tr>
                </tbody>
            </ItemTemplate>
            <FooterTemplate>
                </table>
            </FooterTemplate>
        </asp:Repeater>

Thank you for your help!