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ASP.NET Proxy Page – Used for Cross Domain Requests from AJAX and JavaScript

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19 Aug 2010

One of the pain points with developing AJAX, JavaScript, JQuery, and other client-side behaviors is that JavaScript doesn’t allow for cross domain

This articles was originally at wiki.asp.net but has now been given a new home on CodeProject. Editing rights for this article has been set at Bronze or above, so please go in and edit and update this article to keep it fresh and relevant.

One of the pain points with developing AJAX, JavaScript, JQuery, and other client-side behaviors is that JavaScript doesn’t allow for cross domain request for pulling content. For example, JavaScript code on www.johnchapman.name could not pull content or data from www.bing.com.

One way to overcome this issue is by using a server-side proxy on the site running the JavaScript code. There is already are well documented PHP solutions on the web, however I couldn’t find very many .NET-based solutions. This simple C# code takes the URL passed to it through the URL encoded query string, retrieves the content of the URL and outputs it as if it were content on the site.

Proxy.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net;
using System.IO;

namespace Proxy
{
    public partial class _Proxy : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string proxyURL = string.Empty;
            try
            {
                proxyURL = HttpUtility.UrlDecode(Request.QueryString["u"].ToString());
            }
            catch { }

            if (proxyURL != string.Empty)
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(proxyURL);
                request.Method = "GET";
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();

                if (response.StatusCode.ToString().ToLower() == "ok")
                {
                    string contentType = response.ContentType;
                    Stream content = response.GetResponseStream();
                    StreamReader contentReader = new StreamReader(content);
                    Response.ContentType = contentType;
                    Response.Write(contentReader.ReadToEnd());
                }
            }
        }
    }
}

Proxy.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Proxy.aspx.cs" Inherits="Proxy._Proxy" % >

The Proxy.aspx page is simply blank except for the Page tag. When passing the URL to the query string, it is important that it is URL encoded. This helps to prevent query strings of the remote site URL from interfering with the Proxy page.

Example Usage

yoursite.com/proxy.aspx?u=http%3a%2f%2fwww.google.com

Originally posted: http://www.johnchapman.name/aspnet-proxy-page-cross-domain-requests-from-ajax-and-javascript/

Add all line of code in try catch because error can occur in any line of code

    protected void getWebRequest()
    {

        try
        {

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://www.msn.com");
            request.Method = "GET";
            request.Proxy = null;
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string contentType = response.ContentType;
            Stream content = response.GetResponseStream();
            StreamReader contentReader = new StreamReader(content);
            Response.ContentType = contentType;
            Response.Write(contentReader.ReadToEnd());

        }
        catch (Exception ee)
        {

            Response.Write(ee.Message.ToString());
        }
    }

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