C# – Need Help With HttpWebRequest object

asp.netc++

I'm trying to build a proxy module for .NET, but I'm having trouble copying the Headers from the current request to the new request. I am setting the headers of the new request, because I want the proxy to support SOAP requests. Here is a portion of my code. I can post everything if need, but this is the only part that seems related to the issue I am having:


HttpApplication app = (HttpApplication)sender;   // sender from context.BeginRequest event
HttpRequest crntReq = app.Request;  // set a reference to request object for easier access

HttpWebRequest proxyReq = (HttpWebRequest)HttpWebRequest.Create(crntReq.Url.AbsoluteUri);

// parse headers from current httpcontext.request.headers and add each name->value to the 
// new request object
foreach (string header in crntReq.Headers)
{    
    proxyReq.Headers.Add(header, crntReq.Headers[header]);      // throws exception :(                  
}

When my code hits the foreach loop, it throws an exception for the Headers.Add function. I'm assuming the collection has access restrictions, for security purposes. It appears that some of the header values are accessible with properties for the HttpWebRequest object itself. However in this case I'd rather get rid of the abstraction and set the properties manually. The exception that I'm receiving is:
{"This header must be modified using the appropriate property.\r\nParameter name: name"}

Thanks in advance for your help,

CJAM

Best Solution

Some of the headers are actually exposed as properties directly on the HttpWebRequest object. These headers you are not allowed to set directly. e.g HttpWebRequest,ContentType and HttpWebRequest.UserAgent

You will need to update these properties directly and avoid setting them via the Headers property.

Related Solutions

C# – Cannot set some HTTP headers when using System.Net.WebRequest

If you need the short and technical answer go right to the last section of the answer.

If you want to know better, read it all, and i hope you'll enjoy...

I countered this problem too today, and what i discovered today is that:

the above answers are true, as:

1.1 it's telling you that the header you are trying to add already exist and you should then modify its value using the appropriate property (the indexer, for instance), instead of trying to add it again.

1.2 Anytime you're changing the headers of an HttpWebRequest, you need to use the appropriate properties on the object itself, if they exist.

Thanks FOR and Jvenema for the leading guidelines...

But, What i found out, and that was the missing piece in the puzzle is that:

2.1 The WebHeaderCollection class is generally accessed through WebRequest.Headers or WebResponse.Headers. Some common headers are considered restricted and are either exposed directly by the API (such as Content-Type) or protected by the system and cannot be changed.

The restricted headers are:

Accept
Connection
Content-Length
Content-Type
Date
Expect
Host
If-Modified-Since
Range
Referer
Transfer-Encoding
User-Agent
Proxy-Connection

So, next time you are facing this exception and don't know how to solve this, remember that there are some restricted headers, and the solution is to modify their values using the appropriate property explicitly from the WebRequest/HttpWebRequest class.

Edit: (useful, from comments, comment by user Kaido)

Solution is to check if the header exists already or is restricted (WebHeaderCollection.IsRestricted(key)) before calling add

C# – How to get the client’s IP address in ASP.NET MVC

The simple answer is to use the HttpRequest.UserHostAddress property.

Example: From within a Controller:

using System;
using System.Web.Mvc;

namespace Mvc.Controllers
{
    public class HomeController : ClientController
    {
        public ActionResult Index()
        {
            string ip = Request.UserHostAddress;

            ...
        }
    }
}

Example: From within a helper class:

using System.Web;

namespace Mvc.Helpers
{
    public static class HelperClass
    {
        public static string GetIPHelper()
        {
            string ip = HttpContext.Current.Request.UserHostAddress;
            ..
        }
    }
}

BUT, if the request has been passed on by one, or more, proxy servers then the IP address returned by HttpRequest.UserHostAddress property will be the IP address of the last proxy server that relayed the request.

Proxy servers MAY use the de facto standard of placing the client's IP address in the X-Forwarded-For HTTP header. Aside from there is no guarantee that a request has a X-Forwarded-For header, there is also no guarantee that the X-Forwarded-For hasn't been SPOOFED.

Original Answer

Request.UserHostAddress

The above code provides the Client's IP address without resorting to looking up a collection. The Request property is available within Controllers (or Views). Therefore instead of passing a Page class to your function you can pass a Request object to get the same result:

public static string getIPAddress(HttpRequestBase request)
{
    string szRemoteAddr = request.UserHostAddress;
    string szXForwardedFor = request.ServerVariables["X_FORWARDED_FOR"];
    string szIP = "";

    if (szXForwardedFor == null)
    {
        szIP = szRemoteAddr;
    }
    else
    {
        szIP = szXForwardedFor;
        if (szIP.IndexOf(",") > 0)
        {
            string [] arIPs = szIP.Split(',');

            foreach (string item in arIPs)
            {
                if (!isPrivateIP(item))
                {
                    return item;
                }
            }
        }
    }
    return szIP;
}

Best Solution

Related Solutions

C# – Cannot set some HTTP headers when using System.Net.WebRequest

C# – How to get the client’s IP address in ASP.NET MVC

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