Web API and HTTP Module

Question

We have an HTTP Module that decodes all encoded requests. It works great with all WCF requests, but NOT in Web Api requests- in Web Api the request (both POST and GET) gets to the service still encoded

I see that it Hits the HTTP Module but,again,still gets to the service encoded. How can i fix it? or what am i doing wrong? i know that its better to work with Message Handlers in Web Api, but HTTP Modules suppose to work too- no?

HTTP Module:

public void Init(HttpApplication context)
    {
        context.BeginRequest += new EventHandler(context_BeginRequest);
        context.EndRequest += context_PreSendRequestContent;
    }

    void context_PreSendRequestContent(object sender, EventArgs e)
    {
        string encodedQuerystring = HttpContext.Current.Request.QueryString.ToString();
        if (!string.IsNullOrEmpty(encodedQuerystring))
        {
            System.Collections.Specialized.NameValueCollection col = new System.Collections.Specialized.NameValueCollection();
            col.Add("q", encodedQuerystring);
            WebFunction.CreateQuerystring(HttpContext.Current, col);
        }


    }

    void context_BeginRequest(object sender, EventArgs e)
    {
        string encodedQueryString = String.Empty;
        if (HttpContext.Current.Request.QueryString.Count > 0 && HttpContext.Current.Request.QueryString["q"] != null)
        {

            object _p = HttpContext.Current.Request.QueryString;
            encodedQueryString = HttpContext.Current.Server.UrlDecode(HttpContext.Current.Request.QueryString["q"].ToString());

            string originalQueryString = HttpContext.Current.Server.UrlDecode(WebFunction.Base64Decode(encodedQueryString));

            if (!string.IsNullOrEmpty(originalQueryString))
            {
                WebFunction.CreateQuerystring(HttpContext.Current, WebFunction.ConvertQueryToCollection(originalQueryString));

            }
        }
    }

WebFunction:

 public static void CreateQuerystring(HttpContext context, System.Collections.Specialized.NameValueCollection nameValueCollection)
    {
        // reflect to readonly property
            PropertyInfo isreadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
            // make collection editable
            isreadonly.SetValue(context.Request.QueryString, false, null);
            context.Request.QueryString.Clear();
            context.Request.QueryString.Add(nameValueCollection);         
            // make collection readonly again
            isreadonly.SetValue(context.Request.QueryString, true, null);            
    }

Web Api:

  public class NamesController : ApiController
{
    [HttpGet]
    [ActionName("GET_NAMES")]
    public Drugs_ResponseData Get(string q)
    {
//need to add the decode function to get it to work
        string[] arrAmpersant = Commonnn.DecodeFrom64(q).Split('&');

        Names_obj = new Names();
        return _obj.GetResult(Convert.ToInt32(Commonnn.GetValFromEqual(arrAmpersant[0])));
    }
}

Answer 1

It seems that the Web API doesn't use the QueryString collection in the request, but it parses the URL itself.

See the GetQueryNameValuePairs method in this file - they take the Uri and parse its Query property.

So you have two options to do that:

1. The dirty one is to change the Uri of the request in your the HTTP module. I don't know whether it's possible, but some reflection could do the trick.
2. The nicer way would be to use the Web API message handler.

Answer 2

May I suggest you use Context.Items and let the QueryString have the encoded version.

It's a not very well known built in key/value dictionary which last throughout a request where you easily store any object and then share it between module, handlers, etc.

Using this would very like give you a better performance than unlocking the QueryString object, but more importantly, you process the value in one place and reuse it in many, and when needed, you just add a second value, the complete QueryString collection or any other value you want to share across a request.

void context_BeginRequest(object sender, EventArgs e)
{
    string encodedQueryString = String.Empty;
    if (HttpContext.Current.Request.QueryString.Count > 0 && HttpContext.Current.Request.QueryString["q"] != null)
    {

        string encodedQueryString = HttpContext.Current.Server.UrlDecode(HttpContext.Current.Request.QueryString["q"].ToString());

        HttpContext.Current.Items("qs_d") = HttpContext.Current.Server.UrlDecode(WebFunction.Base64Decode(encodedQueryString));

    }
}

Web Api:

public class NamesController : ApiController
{
  [HttpGet]
  [ActionName("GET_NAMES")]
  public Drugs_ResponseData Get(string q)
  {
    string[] arrAmpersant = Commonnn.DecodeFrom64(HttpContext.Current.Items("qs_d").ToString()).Split('&');

    Names_obj = new Names();
    return _obj.GetResult(Convert.ToInt32(Commonnn.GetValFromEqual(arrAmpersant[0])));
  }
}

Side note: I see you call HttpContext.Current.Server.UrlDecode twice. I don't think you need that unless your Base64Decode method encode the value again.