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I am using Oauth2 to get information about a user from Facebook. The result I get is in a JSON format, but when I try to parse it using JSON.NET I get an error saying: Exception : System.ArgumentException: Incomplete JSON input. At line 1, column 0.

Sample code:

request.GetResponseAsync().ContinueWith(t =>{
if(!t.IsFaulted && !t.IsCanceled){
    try{
        Console.WriteLine(t.Result.GetResponseText());

        dynamic obj = JsonObject.Parse(t.Result.GetResponseText());
        Console.WriteLine(obj.first_name);

    } catch (Exception e) {
        Console.WriteLine("Exception : "+ e);
    }
  }
});

The t.Result.GetResponseText() method returns a string in this format:

{
"id":"some_id",
"bio":"some_bio",
"first_name":"some_name",
"gender":"male",
"last_name":"some_name",
"link":"https:\/\/www.facebook.com\/app_scoped_user_id\/some_user_id\/",
"locale":"nb_NO",
"middle_name":"some_name",
"name":"some_name",
"timezone":1,
"updated_time":"2014-09-18T12:48:34+0000",
"verified":true
}

Are someone able to point out what I am missing here? Thanks in advance!

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  • Have you debugged and that's what you're getting? JSON seems to be valid... Commented Feb 5, 2015 at 12:15
  • This is the error message. I also think that the JSON seems to be valid. So i dont understand. Exception : System.ArgumentException: Incomplete JSON input. At line 1, column 0 at System.Runtime.Serialization.Json.JavaScriptReader.ReadCore () [0x00225] in ///Library/Frameworks/Xamarin.iOS.framework/Versions/8.6.0.51/src/mono/mcs/class/System.ServiceModel.Web/System.Runtime.Serialization.Json/ Commented Feb 5, 2015 at 12:19

3 Answers 3

Reset to default
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Create a class which can deserialize the given json data

public class Rootobject
        {
            public string id { get; set; }
            public string bio { get; set; }
            public string first_name { get; set; }
            public string gender { get; set; }
            public string last_name { get; set; }
            public string link { get; set; }
            public string locale { get; set; }
            public string middle_name { get; set; }
            public string name { get; set; }
            public int timezone { get; set; }
            public DateTime updated_time { get; set; }
            public bool verified { get; set; }
        }

then deserialize the json data using JSON.NET

var data = Newtonsoft.Json.JsonConvert.DeserializeObject<Rootobject>(t.Result.GetResponseText());

Worked for me
Hope this helps

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2 Comments

I no longer get the JSON error message, but if I try to output anything from the data-object like Console.WriteLine(data.id), I get a NullReferenceException. Do you get it to?
Edit: Strange. If I copy the JSON string in a string variable and then use it in the deserialize-method, the data-object is not null. If i use the t.Result.GetResponseText() the data-object is null.
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The error message indicates that the response text is an empty string (incomplete JSON input, first line, first character).

Just a hunch: does the problem resolve itself if you store the response text in a temporary variable?

var responseText = t.Result.GetResponseText();
Console.WriteLine(responseText);
dynamic obj = JsonObject.Parse(responseText);

The reason why this works is that t.Result.GetResponseText() only returns a value the first time that you call it. The underlying stream does not support seeking, and the JSON reader does not cache the value internally.

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5 Comments

No it does not, however if I copy the JSON string in a string variable and then use it in the deserialize-method, the data-object is not null. If i use the t.Result.GetResponseText() the data-object is null. if i i store the response text in a temporary variable the data-object is also null.
So clearly the return value of t.Result.GetResponseText() is not the same string as the one that you are pasting in manually.
True, but then again I find it weird that when I output t.Result.GetResponseText() I get the exact JSON-string which I wrote in the original post.
My first thought was that GetResponseText() only returns a value the first time that you call it.
Your thought was correct, it does only return a value the first time you call it. Thank you!
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Thanks to Steven Liekens we found out that the t.Result.GetResponseText()method only returns something the first time its called. The second time it returns an empty string.

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