Question

I’ve got a problem using WebClient.UploadStringAsync method. I’ve to do a POST request with some info to an external server, and in that request, I’ve to include the text cointained in a TextBox.

What I do is the following:

Uri url = new Uri("http://www.someweb.com");
string request = "{\"requests\":[\"sendMessage\",{\"body\":\"" + newMessageTextBox.Text + "\"}]}";

WebClient wb = new WebClient();
wb.UploadStringCompleted += new UploadStringCompletedEventHandler(nb_UploadStringCompleted);
wb.UploadStringAsync(url, "Post", request);

There is no problem, but if I include a message with a return, something like
“Hello

everybody”
the server gives back an error. If I sniff my traffic with Wireshark, I can see my POST request but it is as follows:

“{“requests”:[“sendMessage”,{“body”:”Hello

everybody”}]}”

While what I want to send is

“{“requests”:[“sendMessage”,{“body”:”Hello\n\neverybody”}]}”

Any ideas??

Thank you all

Answer 1

Yes, you need to perform appropriate JSON escaping. Personally I would use a JSON library for this – I’ve used Json.NET within Windows Phone 7 and it’s worked fine.

You’d build up your request as a JSON object – so without specifying the JSON text form itself at all – and then ask it to format itself into a string (just by calling ToString). For example:

using System;
using Newtonsoft.Json.Linq;

class Program
{
    static void Main(string[] args)
    {
        string text = "Hello\neverybody";

        JObject json = new JObject 
        {
            { "requests", new JArray 
                {
                    new JObject
                    {
                        { "sendMessage", new JObject 
                            {
                                { "body", text }
                            }
                        }
                    }
                }
            }
        };

        Console.WriteLine(json);
    }
}

Output:

{
  "requests": [
    {
      "sendMessage": {
        "body": "Hello\neverybody"
      }
    }
  ]
}

(Obviously you don’t need to use as much whitespace as that if you don’t want to. You don’t have to use object initializers either.)

EDIT: Okay, with changes as requested:

JObject json = new JObject 
{
    { "sid", sid },
    { "version", "0.6" },
    { "requests", new JArray 
        {
            new JArray
            {
                new JObject
                {
                    { "sendMessage", new JObject 
                        {
                            { "body", text },
                            { "recipient", recipient },
                            { "legacy", false },
                            { "thread_key", threadKey }
                        }
                    }
                }
            }
        }
    }
};

Result:

{
  "sid": "sid",
  "version": "0.6",
  "requests": [
    [
      {
        "sendMessage": {
          "body": "Hello\neverybody",
          "recipient": "[e-mail]",
          "legacy": false,
          "thread_key": "T1"
        }
      }
    ]
  ]
}