Custom Item Template Return in a nested repeater

I'm new at this and I'm not sure if I'm even doing it right.
I'm tring to find out if an event has been chosen. I've tried everything and I keep getting CS1502: The best overloaded method match for 'System.Convert.ToString(object)' has some invalid arguments error. My code is:

 <asp:repeater id="parentRepeater" runat="server">
   <itemtemplate><br>

     <span class="week"> <%# DataBinder.Eval(Container.DataItem,"Title") %></span><br><br>


      <!-- start child repeater -->
      <asp:repeater id="childRepeater" datasource='<%# ((DataRowView)Container.DataItem)
      .Row.GetChildRows("myrelation") %>' runat="server" EnableViewState="true">

         <itemtemplate>
<table width="100%"  border="0" cellspacing="5">
  <tr>
    <td width="7%">

<%# CheckEvent(Convert.ToInt32(DataBinder.Eval(Container.DataItem,"[\"EventID\"]")))%>
</td>
<td width="93%"><strong><%# DataBinder.Eval(Container.DataItem,"[\"EventName\"]")%>
      </strong></td>
</tr>
</table>


         </itemtemplate>
      </asp:repeater>
      <!-- end child repeater -->

   </itemtemplate>
</asp:repeater>


I've set up the function as:
public void CheckEvent(int ids) {

//I'm trying to have it check to see if the event was chosen after the page has been submitted.
if(IsPostBack) {

}
}
I've taken everything out of the function, but it still doesn't work. The error comes up at the line the function was called on.

Thanks!