how do I handle and deflate a GZipped form post in asp.net MVC? - asp.net

Question

I have an iPad app that submits orders to an ASP.NET MVC web site via form post. It is posting JSON which can be fairly large for a mobile device to send (200~300K) under certain conditions. I can GZip the form post but then my asp.net mvc chokes on the gzipped content.
How can I handle a GZipped form post in asp.net mvc?
UPDATE:
Darin's answer puts me on the right track but I still have no idea how to do what he suggests, so here is where I am at:
Have this code to decompress a string:
http://dotnet-snippets.com/dns/compress-and-decompress-strings-SID612.aspx
And I get the string like so:
StreamReader reader = new StreamReader(Request.InputStream);
string encodedString = reader.ReadToEnd();
but this gives me the error:
The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or a non-white space character among the padding characters.
EDIT - COMPLETED CODE
I am using asp.net MVC and this is working great for me. I also had to deal with some other encoding that happens when my gzipping occurs:
[Authorize]
[HttpPost]
[ValidateInput(false)]
public ActionResult SubmitOrder()
{
GZipStream zipStream = new GZipStream(Request.InputStream, CompressionMode.Decompress);
byte[] streamBytes = ReadAllBytes(zipStream);
var result = Convert.ToBase64String(streamBytes);
string sample = System.Text.Encoding.UTF8.GetString(Convert.FromBase64String(result));
string escaped = Uri.UnescapeDataString(sample);
// escaped now has my form values as a string like so: var1=value1&var2=value2&ect...
//more boring code
}
public static byte[] ReadAllBytes(Stream input)
{
byte[] buffer = new byte[16 * 1024];
using (MemoryStream ms = new MemoryStream())
{
int read;
while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
{
ms.Write(buffer, 0, read);
}
return ms.ToArray();
}
}

Answer 1

You can do this without a custom model binder. Write an Action that accepts HttpPostedFileBase, i.e, treat this as a file upload.
[HttpPost]
public ActionResult UploadCompressedJSON(HttpPostedFileBase file)
{
if (file != null && file.ContentLength > 0)
{
GZipStream zipStream = new GZipStream(file.InputStream, CompressionMode.Decompress);
byte[] streamBytes = ReadAllBytes(zipStream);
var result = Convert.ToBase64String(streamBytes);
}
return RedirectToAction("Index");
}
You are going to need to change your client side code to send a file upload request but that should be fairly easy. For example you can look at this code.

Answer 2

How can I handle a GZipped form post in asp.net mvc?
You could write a custom model binder that will directly read the Request.InputStream, unzip it and then parse the contents and instantiate some view model you want to bind to.

Answer 3

Use the System.IO.Compression.GZipStream class.
Codeproject example