Incorrect encoding and decoding in C#

Question

I am trying to upload a base64 encoded string from my mobile phone app (which is written in C#). The string represents an image that needs to be uploaded to my server, which is also written in C#. My client-side code looks like the following:

Client Side Code
----------------
Dictionary<string, string> parameters = new Dictionary<string, string>();
parameters.Add("username", GetUserName());
parameters.Add("imageBytes", Convert.ToBase64String(this.ImageBytes));

string data = string.Empty;
foreach (string key in parameters.Keys)
{
  data += key;
  data += "=";
  data += parameters[key];
  data += "&";
}
data = data.Substring(0, data.Length - 1);

uploadWebRequest = (HttpWebRequest)(ar.AsyncState);
using (Stream postStream = uploadWebRequest.EndGetRequestStream(ar))
{
  byte[] byteArray = Encoding.UTF8.GetBytes(data);  // I believe this has something to do with it. But I believe this is correct. So I think something needs to be done on the server
  postStream.Write(byteArray, 0, byteArray.Length);
  postStream.Flush();
  postStream.Close();
}
uploadWebRequest.BeginGetResponse(new AsyncCallback(Upload_Completed), uploadWebRequest);

when I print out Convert.ToBase64String(this.ImageBytes) in the Watch Window, I receive the following:

Encoded Client String
---------------------
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On my server side, I have the following:

Server Side Code
----------------
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult AddPicture(string username, string imageBytes)
{
  WriteToTempFileForDebugging(imageBytes);
  byte[] tempBytes = Convert.FromBase64String(imageBytes);
  using (MemoryStream memoryStream = new MemoryStream(tempBytes))
  {
    memoryStream.Position = 0;
    System.Drawing.Image image = System.Drawing.Image.FromStream(memoryStream);
    image.Save("C:\\inetpub\\wwwroot\\MySite\\Pictures\\myImage.png");
  }
}

when this code executes, the Image.FromStream(...) line throws an exception. The error says: System.ArgumentException Parameter is not valid. Because of that, I print the 'imageBytes' string to a temporary file. The contents of that temporary file look exactly the same as the encoded string above, with one exception. All of the spaces (" ") in the encoded string have been replaced with plus signs ("+"). I'm guessing this is some encoding issue. However, I'm not sure how to fix it. I don't want to do a find and replace.

How do I resolve this in the proper manner?

Thank you!

Yes, it's the URL parameter encoding that'll be doing that - specifically parameters.Add("imageBytes", Convert.ToBase64String(this.ImageBytes));. Are you sending the data twice?? Could you POST rather than GET? That might sidestep the encoding issue. — Rup
– Rup, Commented Aug 17, 2012 at 15:03
is "this.ImageBytes" a byte array? You can also use the HttpUtility class to decode the URL parameter (i.e. it will convert the + back to " ") — Jared Peless
– Jared Peless, Commented Aug 17, 2012 at 15:04
I am POSTing. "this.ImageBytes" is a byte array. @Jared: Are you saying on he Server I should use HttpUtility.UrlDecode? — user609886
– user609886, Commented Aug 17, 2012 at 15:31
Yes, that is what I am saying... because you have a string that has been URL encoded and you need to decode it from that format prior to getting it back to a base64 string that you will decode to the byte[]. — Jared Peless
– Jared Peless, Commented Aug 17, 2012 at 17:44

SLaks · Accepted Answer · 2012-08-17 15:04:18Z

4

You need to call Uri.EscapeDataString before appending each parameter to the POST string.

answered Aug 17, 2012 at 15:04

SLaks

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3 Comments

user609886 Over a year ago

Does this need to be called in addition to Encoding.UTF8.GetBytes? For instance, should I say: byte[] byteArray = Encoding.UTF8.GetBytes(Uri.EscapeDataString(data));

SLaks Over a year ago

You need to escape each value; not the entire string. But, yes.

user609886 Over a year ago

When I use Uri.EscapeDataString, an Exception is thrown with a message that says "Invalid URI: The Uri string is too long."

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