How to get hold of Content that is already read

Question

I have a class that inherits from ApiController. It has a Put-method like this:

[PUT("user/{UserId}")]
public HttpResponseMessage Put(string userId, PaymentRequest paymentRequest)
{
    // Calling business logic and so forth here
    // Return proper HttpResponseMessage here
}

The method works fine as it is above. Now I need to validate the signature of the method call, but here I run into a problem. The signature is essentially a combination of method + url + body. The method I can get by calling Request.Method and the url I can get by calling Request.RequestUri.ToString(), but I can't get hold of the body as it was before it was automatically deserialized into a PaymentRequest object by the asp.net MVC4 framework.

My first try: As I have now understood Request.Content.ReadAsStringAsync().Result returns nothing. This is because the content can only be read once.

My second try: I tried to serialize it back to a JSON string.

var serializer = new JavaScriptSerializer();
var paymentRequestAsJson = serializer.Serialize(paymentRequest);

The problem with this is that the formatting turns out slightly different than the body part of the signature. It has the same data, but some more spaces.

I can't change what the caller of my Put-method does, as this is a third party component. What should I do?

Answer 1

A very delayed response, but recently I have had the same challenge to overcome.

I have approached that a bit different without having to get the data from the httpContext (can be quite costly for high volume transaction web application).

I created a simple interface and made each Controller implementing it:

public interface IBaseControllerData
{
    object Entity { get; set; }
}

I have then set the Controller's Entity property to the Json payload for each post and put action. Finally, I retrieved the Entity data within the ActionFilterAttribute.OnActionExecuted overridden method and serialised it to Json before injecting into MongoDB:

object entity = ((IBaseControllerData)actionExecutedContext.ActionContext.ControllerContext.Controller).Entity;
                    requestBody = Newtonsoft.Json.JsonConvert.SerializeObject(entity);

Hope that helps !

Cheers

Answer 2

You could read from the underlying request:

using (var stream = new MemoryStream())
{
    var context = (HttpContextBase)Request.Properties["MS_HttpContext"];
    context.Request.InputStream.Seek(0, SeekOrigin.Begin);
    context.Request.InputStream.CopyTo(stream);
    string requestBody = Encoding.UTF8.GetString(stream.ToArray());
}

Answer 3

Don't include the body parameter in the signature and that will allow you to buffer the content and read the content as many times as you like.

[PUT("user/{UserId}")]
public HttpResponseMessage Put(string userId)
{
    Request.Content.LoadIntoBufferAsync().Wait();
    var paymentRequest = Request.Content.ReadAsAsync<PaymentRequest>().Result;
    var requestBody = Request.Content.ReadAsStringAsync().Result;
    // Calling business logic and so forth here
    // Return proper HttpResponseMessage here
}