Silverlight access an ashx JSON response - c#

I have a Silverlight application that is calling out to an ashx that is hosted in the same application as the Silverlight control.
The ashx does the following (stripped down):
// Basic object
class SomeObject
{
int ID { get; set; }
string Description { get; set; }
double Value { get; set; }
}
// ASHX details
DataLayer dl = GetDataLayer();
List<SomeObject> lst = dl.ListObjects();
string result = "";
if (lst != null)
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
result = serializer.Serialize(lst);
}
context.Response.ContentType = "application/json";
context.Response.Write(result);
context.Response.End();
Now the part I am having trouble with is what to do with the ashx on my Silverlight control.
I am looking to call the ashx and then map the JSON result into my internal silverlight objects. Seems like a pretty simple task but I am not sure how to access the ashx or deal with the response from it. Since Silverlight has a stripped down version of .NET it is throwing me for off.
Any help / suggestions?
Using Silverlight 3, ASP.NET 3.5.

Use System.Json to load the string into a JsonArray. JsonValue.Load() takes a response stream and can populate a JsonArray - from there, you can either iterate through or use LINQ to query the values.
Links:
Working with JSON Data on MSDN
JsonValue.Load on MSDN
Blog post with some sample code

Thanks for the reply Jon. Your links helped me figure it out and I thought I should include the code I used in this question for others that come across this question in the future.
Two ways of handling the Json. For both methods you need to setup a handler to get the Json data.
// This gets the URL to call to get the Json data
Uri uri = GetSomeUrl();
WebClient downloader = new WebClient();
downloader.OpenReadCompleted += new OpenReadCompletedEventHandler(downloader_OpenReadCompleted);
downloader.OpenReadAsync(uri);
You then need to implement the event handler downloader_OpenReadCompleted specified above with the code to handle the Json. In both case the code below should be wrapped in a using statement:
using (System.IO.Stream strResult = e.Result)
{
}
First way to handle the Json data that is part of the Silverlight framework is to add a reference to System.Json.
JsonArray jsonArray = (JsonArray)JsonArray.Load(e.Result);
List<SomeObject> lst = new List<SomeObject>();
foreach (System.Json.JsonObject obj in jsonArray)
{
SomeObject obj = new SomeObject();
obj.ID = int.Parse(obj["ID"].ToString();
obj.Description = obj["Description"].ToString();
obj.Value = double.Parse(obj["Value"].ToString());
lst.Add(obj);
}
The other way that is possible with or without Silverlight is:
System.Runtime.Serialization.Json.DataContractJsonSerializer serializer =
new System.Runtime.Serialization.Json.DataContractJsonSerializer(typeof(List<SomeObject>));
List<SomeObject> lst = (List<SomeObject>)(serializer.ReadObject(strResult));
Both methods end up getting me a list of my objects which I can then use as I see fit.
Thanks for the help Jon!

Related

System.Text.Json.JsonException: The JSON value could not be converted

I'm using Ubuntu and dotnet 3.1, running vscode's c# extension.
I need to create a List from a JSON file, my controller will do some calculations with this model List that I will pass to it
So, here is my code and the error I'm getting.
First, I thought my error was because at model my attributes were char and C#, for what I saw, cannot interpret double-quotes for char, it should be single quotes. Before losing time removing it, I just changed my type declarations to strings and it's the same error.
Can someone help me?
ElevadorModel
using System.Collections.Generic;
namespace Bla
{
public class ElevadorModel
{
public int andar { get; set; }
public string elevador { get; set; }
public string turno { get; set; }
}
}
Program.cs:
class Program
{
static void Main(string[] args)
{
var path = "../input.json";
string jsonString;
ElevadorModel elevadoresModel = new ElevadorModel();
jsonString = File.ReadAllText(path); //GetType().Name = String
Console.WriteLine(jsonString); //WORKS
elevadoresModel = JsonSerializer.Deserialize<ElevadorModel>(jsonString);
}
JSON:
Your input json has an array as the base token, whereas you're expecting an object. You need to change your deserialization to an array of objects.
var elevadoresModels = JsonSerializer.Deserialize<List<ElevadorModel>>(jsonString);
elevadoresModel = elavoresModels.First();
Your input JSON is an array of models, however you're trying to deserialize it to a single model.
var models = JsonSerializer.Deserialize<List<ElevadorModel>>(jsonString);
This is also a problem in Blazor-Client side. For those calling a single object
e.g ClassName = await Http.GetFromJsonAsync<ClassName>($"api/ClassName/{id}");
This will fail to Deserialize. Using the same System.Text.Json it can be done by:
List<ClassName> ListName = await Http.GetFromJsonAsync<List<ClassName>>($"api/ClassName/{id}");
You can use an array or a list. For some reason System.Text.Json, does not give errors and it is successfully able Deserialize.
To access your object, knowing that it is a single object use:
ListName[0].Property
In your case the latter solution is fine but with the path as the input.
In my case, I was pulling the JSON data to deserialize out of an HTTP response body. It looked like this:
var resp = await _client.GetAsync($"{endpoint}");
var respBody = await resp.Content.ReadAsStringAsync();
var listOfInstances = JsonSerializer.Deserialize<List<modelType>>(respBody);
And the error would show up. Upon further investigation, I found the respBody string had the JSON base object (an array) wrapped in double quotes...something like this:
"[{\"prop\":\"value\"},...]"
So I added
respBody = respBody.Trim('\"');
And the error changed! Now it was pointing to an invalid character '\'.
I changed that line to include
respBody = respBody.Trim('\"').Replace("\\", "");
and it began to deserialize perfectly.
For reference:
var resp = await _client.GetAsync($"{endpoint}");
var respBody = await resp.Content.ReadAsStringAsync();
respBody = respBody.Trim('\"').Replace("\\", "");
var listOfInstances = JsonSerializer.Deserialize<List<modelType>>(respBody);

Adding object to JSON file

I'm creating a software on which I added a profiles feature where the user can create profile to load his informations faster. To store these informations, I'm using a JSON file, which contains as much objects as there are profiles.
Here is the format of the JSON file when a profile is contained (not the actual one, an example) :
{
"Profile-name": {
"form_email": "example#example.com",
//Many other informations...
}
}
Here is the code I'm using to write the JSON and its content :
string json = File.ReadAllText("profiles.json");
dynamic profiles = JsonConvert.DeserializeObject(json);
if (profiles == null)
{
File.WriteAllText(jsonFilePath, "{}");
json = File.ReadAllText(jsonFilePath);
profiles = JsonConvert.DeserializeObject<Dictionary<string, Profile_Name>>(json);
}
profiles.Add(profile_name.Text, new Profile_Name { form_email = form_email.Text });
var newJson = JsonConvert.SerializeObject(profiles, Formatting.Indented);
File.WriteAllText(jsonFilePath, newJson);
profile_tr.Nodes.Add(profile_name.Text, profile_name.Text);
debug_tb.Text += newJson;
But when the profiles.json file is completely empty, the profile is successfully written, but when I'm trying to ADD a profile when another one already exists, I get this error :
The best overloaded method match for 'Newtonsoft.Json.Linq.JObject.Add(string, Newtonsoft.Json.Linq.JToken)' has some invalid arguments on the profiles.Add(); line.
By the way, you can notice that I need to add {} by a non-trivial way in the file if it's empty, maybe it has something to do with the error ?
The expected output would be this JSON file :
{
"Profile-name": {
"form_email": "example#example.com",
//Many other informations...
},
"Second-profile": {
"form_email": "anotherexample#example.com"
//Some other informations...
}
}
Okay so I found by reading my code again, so I just replaced dynamic profiles = JsonConvert.DeserializeObject(json); to dynamic profiles = JsonConvert.DeserializeObject<Dictionary<string, Profile_Name>>(json);.
But it still don't fix the non-trivial way I use to add the {} to my file...
The object the first DeserializeObject method returns is actually a JObject, but below you deserialize it as a Dictionary. You shouldn't be mixing the types, choose either one.
If you use the JObject then to add objects you need to convert them to JObjects:
profiles.Add(profile_name.Text, JObject.FromObject(new Profile_Name { form_email = form_email.Text }));
In both cases, when the profile is null you just need to initialize it:
if (profiles == null)
{
profiles = new JObject(); // or new Dictionary<string, Profile_Name>();
}

Reading CollectionJson content in Web Api Project

I have a project similar(Almost identical) to Conference API project which is taking similar approach to the noted project for returning CollectionJson content. I am having difficulty Setting the Collection property of the ReadDocument (Line 30) as it does not have any setter. I could bypass this problem by doing the following change
public CollectionJsonContent(Collection collection)
{
var serializerSettings = new JsonSerializerSettings
{
NullValueHandling = NullValueHandling.Ignore,
Formatting = Newtonsoft.Json.Formatting.Indented,
ContractResolver = new CamelCasePropertyNamesContractResolver()
};
collection.Version = "1.0";
Headers.ContentType = new MediaTypeHeaderValue("application/vnd.collection+json");
using (var writer = new JsonTextWriter(new StreamWriter(_memoryStream)){CloseOutput = false})
{
//var readDocument = new ReadDocument(); {IReadDocument.Collection = collection};
var serializer = JsonSerializer.Create(serializerSettings);
serializer.Serialize(writer,collection);
writer.Flush();
}
_memoryStream.Position = 0;
}
Although above code compiles and to some extent sorts out the problem but then again I will have another problem of not being able to consume the JsonCollection content in my controller unit tests. Consider the following unit test code snippet:
using (var request = CreateRequest())
{
var controller = new TestController(DataService) {Request = request};
var temp = await controller.ListAsync(gridSearchData, sampleSearchData);
if ((temp is NotFoundResult) && (sampleCollection.Any()))
{
Assert.Fail("Controller did not return any result but query did");
}
var json = await temp.ExecuteAsync(cancellationTokenSource);
var readDocument = json.Content.ReadAsAsync<ReadDocument>(new[] {new CollectionJsonFormatter()}, cancellationTokenSource).Result;
}
Since I did not set the collection property of ReadDocument readDocument is always empty and I cant read its content.
How do you asynchronously read the contents of JsonCollection on the client side in WEB API projects?
To get a Clear picture of the approach look at the Conference Web Api
and the authors blog
OK all, this has been fixed. The Collection property is now settable again.
I have just pushed release 0.7.0 with this fix, a major naming refactoring as well as a nice improvement to serialization to not write out empty collections.
Please see the release notes for the changes (especially the naming as the package names and namespaces have changed)
As far as I see from your code, you do not serialize a ReadDocument object, but only a property of it (Collection), and then you try to deserialize that value into a new ReadDocument object.
A sample ReadDocument should serialize like this
"{"Collection": [1,2,3,4,5] }"
But you serialize collection, so you get
"[1,2,3,4,5]"
I recommend a surrogate class for serialization like this
class SerializableReadDocument
{
public Collection Collection { get; set; }
}
and update your serialization code like this
using (var writer = new JsonTextWriter(new StreamWriter(_memoryStream)){CloseOutput = false})
{
var readDocument = new SerializableReadDocument() { Collection = collection };
var serializer = JsonSerializer.Create(serializerSettings);
serializer.Serialize(writer, readDocument);
writer.Flush();
}
But, this will not resolve your problem when you try to deserialize your output since ReadDocument does not have a settable Collection property, deserialization will either fail, or return a ReadDocument object with an empty Collection.
You can use SerializableReadDocument if you like in your unit tests.
I am looking into this and will come up with a solution hopeful this weekend, which will either be to make it a public setter, or make the setter internal and have public ctor that accepts a collection.
Sorry for the difficulty.

storing JSON data in db

I'm trying to store data from fb wall into database.
My *.cs code
public ActionResult GetWall()
{
JSONObject wallData = helper.Get("/me/feed");
if (wallData != null)
{
var data = wallData.Dictionary["data"];
List<JSONObject> wallPosts = data.Array.ToList<JSONObject>();
ViewData["Wall"] = wallPosts;
}
return View("Index");
}
Which gets posts from fb wall.
And then I have an *.aspx file, which "breaks" my wallposts into pieces (objects) or whatever you like to call them.
foreach (Facebook.JSONObject wallItem in wallPosts)
{
string wallItemType = wallItem.Dictionary["type"].String;
//AND SO ON...
What i'm trying to say is that I can access to elements inside fb JSON.
Is there a way i can access to the JSON elements inside *.cs file.
Or is there a way I can store elements inside the *.aspx file to db?
And if its possible, I would like to know how. =)
Thanks for help
Don't use the SDK. Fetch the JSON Data using HttpWebRequest and then Deserialize it using System.Runtime.Serialization.Json.DataContractJsonSerializer. You just have to Create a class with same properties returned in JSON data. See the example below
string Response = Utilities.HttpUtility.Fetch("https://graph.facebook.com/me?access_token=" + AccessToken, "GET", string.Empty);
using (System.IO.MemoryStream oStream = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(Response)))
{
oStream.Position = 0;
return (Models.FacebookUser)new System.Runtime.Serialization.Json.DataContractJsonSerializer(typeof(Models.FacebookUser)).ReadObject(oStream);
}
I'm not familiar with the facebook API and the question isn't too clear, but I assume that the string wallItemType is itself a JSON string, and you wish to parse it.
I'd use the Json.Net library to parse this.
using Newtonsoft.Json;
//your code as above
foreach (Facebook.JSONObject wallItem in wallPosts)
{
string wallItemType = wallItem.Dictionary["type"].String;
//I assume wallItemType is a JSON string {"name":"foobar"} or similar
JObject o = JObject.Parse(wallItemType);
string name = (string)o["name"]; //returns 'foobar'
//and so on
you can also use the Json.Net to deserialize to a custom type. This custom type could be mapped to a SQL database using NHibernate.
If you wish to store the entire json string in a database, then you could use a document database such as CouchDB.

Persist data using JSON

I'm tryping to use JSON to update records in a database without a postback and I'm having trouble implementing it. This is my first time doing this so I would appreciate being pointed in the right direction.
(Explanation, irrelevant to my question: I am displaying a list of items that are sortable using a jquery plugin. The text of the items can be edited too. When people click submit I want their records to be updated. Functionality will be very similar to this.).
This javascript function creates an array of the objects. I just don't know what to do with them afterwards. It is called by the button's onClick event.
function SaveLinks() {
var list = document.getElementById('sortable1');
var links = [];
for (var i = 0; i < list.childNodes.length; i++) {
var link = {};
link.id = list.childNodes[i].childNodes[0].innerText;
link.title = list.childNodes[i].childNodes[1].innerText;
link.description = list.childNodes[i].childNodes[2].innerText;
link.url = list.childNodes[i].childNodes[3].innerText;
links.push(link);
}
//This is where I don't know what to do with my array.
}
I am trying to get this to call an update method that will persist the information to the database. Here is my codebehind function that will be called from the javascript.
public void SaveList(object o )
{
//cast and process, I assume
}
Any help is appreciated!
I have recently done this. I'm using MVC though it shouldn't be too different.
It's not vital but I find it helpful to create the contracts in JS on the client side and in C# on the server side so you can be sure of your interface.
Here's a bit of sample Javascript (with the jQuery library):
var item = new Item();
item.id = 1;
item.name = 2;
$.post("Item/Save", $.toJSON(item), function(data, testStatus) {
/*User can be notified that the item was saved successfully*/
window.location.reload();
}, "text");
In the above case I am expecting text back from the server but this can be XML, HTML or more JSON.
The server code is something like this:
public ActionResult Save()
{
string json = Request.Form[0];
var serializer = new DataContractJsonSerializer(typeof(JsonItem));
var memoryStream = new MemoryStream(Encoding.Unicode.GetBytes(json));
JsonItem item = (JsonItem)serializer.ReadObject(memoryStream);
memoryStream.Close();
SaveItem(item);
return Content("success");
}
Hope this makes sense.
You don't use CodeBehind for this, you use a new action.
Your action will take an argument which can be materialized from your posted data (which, in your case, is a JavaScript object, not JSON). So you'll need a type like:
public class Link
{
public int? Id { get; set; }
public string Title { get; set; }
public string Description { get; set; }
public string Url { get; set; }
}
Note the nullable int. If you have non-nullable types in your edit models, binding will fail if the user does not submit a value for that property. Using nullable types allows you to detect the null in your controller and give the user an informative message instead of just returning null for the whole model.
Now you add an action:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult DoStuff(IEnumerable<Link> saveList)
{
Repository.SaveLinks(saveList);
return Json(true);
}
Change your JS object to a form that MVC's DefaultModelBinder will understand:
var links = {};
for (var i = 0; i < list.childNodes.length; i++) {
links["id[" + i + "]"] = list.childNodes[i].childNodes[0].innerText;
links["title[" + i + "]"] = list.childNodes[i].childNodes[1].innerText;
links["description[" + i + "]"] = list.childNodes[i].childNodes[2].innerText;
links["url[" + i + "]"] = list.childNodes[i].childNodes[3].innerText;
}
Finally, call the action in your JS:
//This is where I don't know what to do with my array. Now you do!
// presumes jQuery -- this is much easier with jQuery
$.post("/path/to/DoStuff", links, function() {
// success!
},
'json');
Unfortunately, JavaScript does not have a built-in function for serializing a structure to JSON. So if you want to POST some JSON in an Ajax query, you'll either have to munge the string yourself or use a third-party serializer. (jQuery has a a plugin or two that does it, for example.)
That said, you usually don't need to send JSON to the HTTP server to process it. You can simply use an Ajax POST request and encode the form the usual way (application/x-www-form-urlencoded).
You can't send structured data like nested arrays this way, but you might be able to get away with naming the fields in your links structure with a counter. (links.id_1, links.id_2, etc.)
If you do that, then with something like jQuery it's as simple as
jQuery.post( '/foo/yourapp', links, function() { alert 'posted stuff' } );
Then you would have to restructure the data on the server side.

Categories

Resources