aspx c# fill variable in loop foreach

<%@ Page language="c#" Codebehind="syncer.aspx.cs" AutoEventWireup="True" %>
<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Data.OleDb" %>
<%@ Import Namespace="System.Xml" %>
<%@ Import Namespace="System.Xml.Serialization" %>
<%@ Import Namespace="System.IO" %>
<%@ Import Namespace="System.Net" %>
<%@ Import Namespace="System.Text" %>
<%@ Import Namespace="System.Runtime.Serialization.Json" %>

<%
String a;
a = Request.QueryString.Get("todo");
if(a=="sync"){
    string url = Request.Url.GetLeftPart(UriPartial.Path);
    Response.Write(url);

    string strData = url;

    char[] separator = new char[] { '/' };
    string[] strSplitArr = strData.Split(separator);
    string resser;
    foreach (string arrStr in strSplitArr)
    {
        if(arrStr != "AssistAplDataBtrApplyTransport.aspx"){
            resser += arrStr;
        }else{

        }
    }
    Response.Write(resser);
}else{

}

%>