get selected values in repeater control - asp.net

Question

i have a repeater control which shows the list of all available products to show to a customer. this repeater control might have 5 items each, and in each of the itemtemplate in the repeater i have a button which is add to cart. once the user clicks this button i want to get the "ID" of that particular product through VB. please note that sometimes in the aspx page i can easily pass the id to a href="" redirect like this
Dim productid As String = DirectCast(Repeatershowsproducts.Controls(0).FindControl("ID"), Label).Text
it always return me the 1st product ID in the list and i wanted it to select the particular one the user chose after clicking the add to cart button. the user my have clicked the Third product meanwhile its showing the ID of the first product
Heres my aspx code.
<asp:Repeater ID="Repeatershowproducts" runat="server">
<ItemTemplate>
<div class="prtm-block-content bg-primary overflow-wrapper">
<div style="margin-top: 15px;" class="left col-xs-3">
<img class="img-responsive img-circle display-ib" src="<%#Eval("productimgpath")%>" alt="Avatar" title="Sponsor Profile Photo">
</div>
<div style="margin-top: 15px;" class="right col-xs-9">
<p class="font-sm"><i class="fa fa-user"></i>FullName: <span class="font-sm mrgn-b-md fw-bold"><%#Eval("productfullname")%></span></p>
<p class="font-sm"><i class="fa fa-bitcoin"></i>Amount: <span style="word-wrap: break-word;" class="font-sm mrgn-b-md fw-bold"><%#Eval("productprice")%> BTC</span></p>
<p class="font-sm"><i class="fa fa-phone"></i>deleivery days: <span class="font-sm mrgn-b-md fw-bold"><%#Eval("productdelivery")%></span></p>
<p class="font-sm"><i class="fa fa-globe"></i>Product location: <span class="font-sm mrgn-b-md fw-bold"><%#Eval("productcountry")%></span></p>
<p class="font-sm">Status: <span class="font-sm mrgn-b-md fw-bold"><%#Eval("Status")%></span></p>
<asp:Label ID="lblproductid" runat="server" Text='<%#Eval("ID")%>'></asp:Label>
</div>
<center>
<div class="text-center center">
<asp:Button ID="Button1" OnClick="addtocart" CssClass="btn btn-lg fw-bold btn-primary btn-rounded" runat="server" Text="Add product to cart" />
</div>
</div>
</center>
</div>
<hr />
</ItemTemplate>
</asp:Repeater>

Answer 1

The easiest way is to change the button from a OnClick to a OnCommand and add a CommandArgument to the button.
<asp:Button ID="Button1" OnCommand="Button1_Command"
CommandArgument='<%# Eval("itemid") %>' runat="server" Text="Add product to cart" />
And then read that value in code behind.
Protected Sub Button1_Command(ByVal sender As Object, ByVal e As CommandEventArgs)
Dim ProductID As Integer = Convert.ToInt32(e.CommandArgument)
End Sub