Two way binding using a Json file in Windows Phone 8.1

Question

I have struggled for more than a month serializing and deserializing a json file.

I can successfully add one line to a json file and deserialize one line. But I can not add more than two lines (or records) to the same json file. And, deserialize successfully. I can add more lines but then I can not deserialize as I seem to add straneous characters to the file. This is building from one of the channel6 examples.

Here is my code:

try

{

           

varmyPersons = newList<Person>();

            

DataContractJsonSerializerdeserialize = newDataContractJsonSerializer(typeof(List<Person>));

            

varmyStream = awaitApplicationData.Current.LocalFolder.OpenStreamForReadAsync(m_PersonFileName);

             myPersons = (

List<Person>)deserialize.ReadObject(myStream);              

             myPersons.Add(

newPerson() { Id = GUIserialization.App.myglobalVariables.iCount, Make = p.Make, Model = p.Model });

             myStream.Dispose();

               

varstream = awaitApplicationData.Current.LocalFolder.OpenStreamForWriteAsync(

            m_PersonFileName,

CreationCollisionOption.OpenIfExists);

              

DataContractJsonSerializerser = newDataContractJsonSerializer(typeof(List<Person>));

              ser.WriteObject(stream, myPersons);

          

// txtResult.Text = ser.ToString();

            txtYear.Text =

"Try"+ GUIserialization.App.myglobalVariables.iCount;

           stream.Dispose();

           GUIserialization.

App.myglobalVariables.iCount += 1;

        }

           

catch{           

           

varmyPersons = newList<Person>();

             myPersons.Add(

newPerson() { Id = GUIserialization.App.myglobalVariables.iCount, Make = p.Make, Model = p.Model });

              

DataContractJsonSerializerser = newDataContractJsonSerializer(typeof(List<Person>));

   

                ser.WriteObject(stream1, myPersons);

            stream1.Position = 0;

           

StreamReadersr = newStreamReader(stream1);

            txtYear.Text =

"Catch"+ GUIserialization.App.myglobalVariables.iCount;

            txtResult.Text = sr.ReadToEnd();

            stream1.Dispose();

            GUIserialization.

App.myglobalVariables.iCount += 1;

            }

This generates this error:

System.Runtime.Serialization.SerializationException was unhandled by user code
  HResult=-2146233076
  Message='{"Id":0,"Make":"VW","Model":"Jetta1"},{"Id":1,"Make":"VW","Model":"Beetle1"}][{"Id":1,"Make":"BMW","Model":"M41"}][{"Id":2,"Make":"Mercedes","Model":"MLK 3501"}]' is not a valid JSON primitive. This error can also occur when extraneous data is present after the JSON data.
  Source=System.ServiceModel.Web
  StackTrace:
       at System.Runtime.Serialization.Json.JavaScriptObjectDeserializer.BasicDeserialize()
       at System.Runtime.Serialization.Json.DataContractJsonSerializer.ReadObject(Stream stream)
       at GUIserialization.readJson.<OnNavigatedTo>d__0.MoveNext()
  InnerException:

Answer 1

Can you post a working sample for testing? Post it to Onedrive and share it here.

---

Matt Small - Microsoft Escalation Engineer - Forum Moderator
If my reply answers your question, please mark this post as answered.

NOTE: If I ask for code, please provide something that I can drop directly into a project and run (including XAML), or an actual application project. I'm trying to help a lot of people, so I don't have time to figure out weird snippets with undefined objects and unknown namespaces.

Answer 2

Matt,

Thank you for your reply.  I am doing per your request. This is a different example that does the exact same thing. I have modified the example to create the two way binding experience.  The example has both a readjsonAsync and deserializejsonAsync function. The read function just returns a stream and that works.

The deserializejsonAsync function gets the error. That is the function that I am calling when the read button is pressed.

The readjsonAsync returns a string and that works fine.

Final question, why is it that the json file that I am creating is not permanent. It disappears from the emulator when I stop the app and restart it.  I event tried loading the app it to my phone. And, the file disappears if I power down my phone. BTW, I can add more than one record to the json file, I just can't deserialize it back to an object.

Thank you Matt for your help.

https://onedrive.live.com/redir?resid=86a2fd89b7bf0a23!6055&authkey=!ABC_jWs86vEuuk0&ithint=folder%2ctxt

Answer 3

I don't see the json file as part of the project - where is it located?

---

Matt Small - Microsoft Escalation Engineer - Forum Moderator
If my reply answers your question, please mark this post as answered.

NOTE: If I ask for code, please provide something that I can drop directly into a project and run (including XAML), or an actual application project. I'm trying to help a lot of people, so I don't have time to figure out weird snippets with undefined objects and unknown namespaces.

Answer 4

Matt,

the json file is created in the app. I only have the object definition in the car.cs file and the name of the file that gets created when you run the app is:

privateconststringJSONFILENAME = "data.json";

But, my idea, maybe I am wrong, is that with the object definition and the file name, I can have my app create the file.

Thank you for your help.

Answer 5

I can't get your code to work at all - it crashes with  System.FormatException.  Is this the problem that you're running into?

---

Matt Small - Microsoft Escalation Engineer - Forum Moderator
If my reply answers your question, please mark this post as answered.

NOTE: If I ask for code, please provide something that I can drop directly into a project and run (including XAML), or an actual application project. I'm trying to help a lot of people, so I don't have time to figure out weird snippets with undefined objects and unknown namespaces.

Answer 6

No, that is not the error.

I recreated the zip file for the entire project.

Here is the new link.

https://onedrive.live.com/redir?resid=86a2fd89b7bf0a23!6108&authkey=!AER9PRHIpvgie64&ithint=folder%2czip

Answer 7

Matt,

Sorry, got any updates?

Answer 8

went back to channel9 and watched http://channel9.msdn.com/Series/Windows-Phone-8-1-Development-for-Absolute-Beginners/Part-22-Storing-and-Retrieving-Serialized-Data

I was adding using statements to the class definition. I removed them and somehow it seems to be working now. I tested it twice and it is working.