Develop Reference

Writing multiple values to json file throws "only one top level item is allowed " error C#

I'm working on a queue management system app, when the person on the counter-press the call next button my program fetches the next person's details using their Id and save them to a JSON file which is then read by a page that displays their name,id, and picture. Now I am able to save a single data but when I save another value the JSON file says "only one top-level item is allowed"
List<ServerToScreen> ScreenData = new List<ServerToScreen>()
{
new ServerToScreen()
{
StudentID=StudentId,
Name = StudentDetails.StudentName,
Photo =StudentDetails.Photo!=null? Convert.ToBase64String( StudentDetails.Photo):NoProfilePic,
HallNo = Result.Where(x=>x.RegisNumber==StudentId).FirstOrDefault().HALLNumber,
TvIP = Result.Where(x=>x.RegisNumber==StudentId).FirstOrDefault().TVIPAddress,
IsCalledOnScreen=false
}
};
string ServerToJson = new JavaScriptSerializer().Serialize(ScreenData);
string path = Server.MapPath("~/TvScreenData/");
System.IO.File.AppendAllText(path + "output.json", ServerToJson);
This is the part of the code that writes the data to JSON file and here is the model i used for the same
public class ServerToScreen {
public string StudentID { get; set; }
public string Name { get; set; }
public string Photo { get; set; }
public string HallNo { get; set; }
public string TvIP { get; set; }
public bool IsCalledOnScreen { get; set; }
}
and the JSON it creates
[
{
"StudentID": "09292",
"Name": "brad pit Aman",
"Photo": "null",
"HallNo": "1",
"TvIP": "192.0.0.1",
"IsCalledOnScreen": false
}
]
[
{
"StudentID": "282828",
"Name": "mani a mani",
"Photo": "null",
"HallNo": "1",
"TvIP": "192.0.0.1",
"IsCalledOnScreen": false
}
]
now somewhere I read that I have to save the list as obj1,obj2 though I understand what it means I couldn't figure out how to do it, I'm really stuck so any help would be great, Thank you.

The issue is caused by adding a new json list to the file every time this method gets called.
What you want to do is first load the json list from this file into your csharp code, then add the new ServerToScreen object to the loaded list, and then replace the json file with the new list.
Code example:
ServerToScreen newObject = new ServerToScreen() {
// create the new ServerToScreen object with all properties
}
var serializer = new JavaScriptSerializer();
string outputPath = Server.MapPath("~/TvScreenData/") + "output.json";
// Load current list from the file
string currentList = System.IO.File.ReadAllText(outputPath);
List<ServerToScreen> screenData = serializer.Deserialize<List<ServerToScreen>>(currentList);
// Add the new object to this list
screenData.Add(newObject);
// Serialize the list including the new object, and replace the file
string jsonWithNewObject = serializer.Serialize(screenData);
System.IO.File.WriteAllText(outputPath, jsonWithNewObject);
Note: code is untested

Newtonsoft.Json.JsonReaderException: 'Unexpected character encountered while parsing value: [.

I'm doing C# JSON <-> PHP JSON for the first time.
Thought I'd get on an easy road but seems like I've hit the rock.
I'm fairly sure that JSON from Newtonsoft allows "[" character but not sure why i have this error instead?
Here's my C# code:
public class SystemJSON
{
public bool Status { get; set; }
public string Message { get; set; }
public string ResponseData { get; set; }
}
public static class SystemCall
{
public static String Post(string uri, NameValueCollection pairs)
{
byte[] response = null;
using (WebClient wc = new WebClient())
{
response = wc.UploadValues(uri, pairs);
}
return Encoding.Default.GetString(response);
}
}
string system_Response = SystemCall.Post("http://127.0.0.1:8080/edsa-NEFS%20(PHP)/api.php", new NameValueCollection()
{
{"do_work", Functions.Get_Department_List.ToString()},
{"api_data", null }
});
**SystemJSON systemJSON = JsonConvert.DeserializeObject<SystemJSON>(system_Response);** //<-- Error happens here.
if(systemJSON.Status == true)
{
//do stuff here
}else
{
MessageBox.Show(this, systemJSON.Message, this.Text, MessageBoxButtons.OK, MessageBoxIcon.Warning);
}
And here's my PHP code:
<?php
// Load Request
$function_name = isset($_POST['do_work']) ? $_POST['do_work'] : '';
$api_data = isset($_POST['api_data']) ? $_POST['api_data'] : '';
// Validate Request
if (empty($function_name))
{
SystemResponse(false, 'Invalid Request');
}
if (!function_exists($function_name))
{
SystemResponse(false, 'API Method Not Implemented');
}
// Call API Method
call_user_func($function_name, $api_data);
/* Helper Function */
function SystemResponse($responseStatus, $responseMessage, $responseData = '')
{
exit(json_encode(array(
'Status' => $responseStatus,
'Message' => $responseMessage,
'ResponseData' => $responseData
)));
}
/* API Methods */
function Get_Department_List($api_data)
{
//Test ------------------------------------------START
$node = array();
$dept = array();
$responseData = array();
$dept['id'] = 1;
$dept['name'] = "General";
$dept['description'] = "Forms, Samples, Templates, Catalogs, etc";
$dept['status'] = 1;
array_push($node, $dept);
$dept['id'] = 2;
$dept['name'] = "Test";
$dept['description'] = "Testing";
$dept['status'] = 1;
array_push($node, $dept);
$responseData["dept"] = $dept;
SystemResponse(true, 'SUCCESS', $responseData);
//Test ------------------------------------------END
}
?>
And here's my error:
Newtonsoft.Json.JsonReaderException HResult=0x80131500
Message=Unexpected character encountered while parsing value: {. Path
'ResponseData', line 1, position 51.

The problem is that your C# SystemJSON class does not match the structure of the incoming JSON correctly.
ResponseData in your C# SystemJSON class is listed as a string but your PHP appears to be pushing out a complex object inside that property. You can't deserialise an object into a string - there is no way for the deserialiser to know how to translate the object structure into a suitable string, and anyway it's not generally a useful or logical thing to do. So instead it throws an error to say the object structure doesn't match.
The specific error you're seeing means the deserialiser is expecting a " to denote the start of a string but instead it's seeing { denoting the start of another object.
Why is this happening? Well, your PHP code will produce a JSON response which looks like this:
{
"Status": true,
"Message": "SUCCESS",
"ResponseData": {
"dept": {
"id": 2,
"name": "Test",
"description": "Testing",
"status": 1
}
}
}
Live demo here
As you can see, ResponseData contains an object, which has a "dept" which in turn is another object with four more properties.
To deserialise this properly, your SystemJSON class will need to be altered, and you'll also need two sub-classes to help it out:
public class SystemJSON
{
public bool Status { get; set; }
public string Message { get; set; }
public ResponseData ResponseData { get; set; }
}
public class ResponseData {
public Department dept {get; set; }
}
public class Department {
public string id {get; set; }
public string description {get; set; }
public int status {get; set; }
}
You will now be able to deserialise the JSON correctly. Here is a live demo of the deserialisation.
P.S the [ character appears to be irrelevant here...it's unclear why you referred to that in your question.
P.P.S. From looking at your PHP I'm guessing that you may be intending to return different data structures in ResponseData depending on which parameter was specified for do_work - i.e. depending on which PHP function is called. If so then you'll need to amend your C# accordingly so that it deserialises to a different concrete class depending on which API method it requests. Or you could possibly cheat and specify ResponseData as dynamic, which will then accept any data structure it received, albeit with the caveat that it's now effectively loosely-typed and so you lose certain benefits when compiling the code such as checking for valid usage of property names, data types etc.

How to Deserialize a JSON array in List (C#)

I am struggling with a subject that has a lot of variants in this forum but I can't seem to find one that suits me, and I think it's because of the way that my JSON array is :(
I'm not an expert but I already manage to "almost" get the end...
I need to get hand in "Success" and "Status" value. But also the different "Addresses".
My JSON (is called responseFromServer):
{
"success":true,
"addresses":
[
{"DPID":658584,"SourceDesc":"Postal\\Physical","FullAddress":"1/8 Jonas Street, Waimataitai, Timaru 7910"},
{"DPID":658585,"SourceDesc":"Postal\\Physical","FullAddress":"2/8 Jonas Street, Waimataitai, Timaru 7910"},
{"DPID":658583,"SourceDesc":"Postal\\Physical","FullAddress":"3/8 Jonas Street, Waimataitai, Timaru 7910"}
],
"status":"success"
}
Then, based on lot of examples in this forum, taking bits and pieces I created my classes:
public class jsonDataTable
{
public bool success { get; set; }
public IEnumerable<dtaddresses> addresses { get; set; }
public string status { get; set; }
}
public class dtaddresses
{
public int DPID { get; set; }
public string SourceDesc { get; set; }
public string FullAddress { get; set; }
}
Then I'm going to Deserialize:
public void _form_OnCallingAction(object sender, ActionEventArgs e)
{
...
...
JavaScriptSerializer js = new JavaScriptSerializer();
jsonDataTable jsonArray = js.Deserialize<jsonDataTable>(responseFromServer);
...
string tb = jsonArray.status.ToString();
string tb2 = jsonArray.success.ToString();
...
...
List<dtaddresses> _listAddresses = new List<dtaddresses>
{
new dtaddresses()
};
...
...
try
{
string tb3 = _listAddresses.Count.ToString();
string tb4 = _listAddresses[0].FullAddress;
}
catch (Exception ex)
{
CurrentContext.Message.Display(ex.Message + ex.StackTrace);
}
...
...
...
CurrentContext.Message.Display("Raw Response from server is: {0}", responseFromServer);
//Returns all the content in a string to check. OK! :)
CurrentContext.Message.Display("The success value is: {0} ", tb);
//Returns the Status Value (in this case "success") OK! :)
CurrentContext.Message.Display("The status value is: {0} ", tb2);
//Returns the Success Value (in this case "true") giggity giggity! All Right! :)
CurrentContext.Message.Display("The n. of addresses is: {0} ", tb3);
//Returns how many addresses ( in this case is returning 0) not ok... :(
CurrentContext.Message.Display("The address value is: {0} ", tb4);
// Returns the Fulladdress in index 0 (in this case nothing...) not ok... :(
Can any one help me to understand why I can access the values in the "dtaddresses" class?
This is the far that I went...

The following piece of code I copied from your question is creating a brand new list that has nothing to do with your deserialized data. Thus it's always going to be a single element list, where the first element contains only default values, which is what you are seeing in tb3 and tb4 later on.
List<dtaddresses> _listAddresses = new List<dtaddresses>
{
new dtaddresses()
};
Instead, assign jsonArray.addresses to _listAddresses, such as:
List<dtaddresses> _listAddresses = jsonArray.addresses.ToList()
Or you can forget about _listAddresses completely, and just simply reference jsonArray.addresses directly, such as:
string tb3 = jsonArray.addresses.Count().ToString();
string tb4 = jsonArray.addresses.First().FullAddress;

Refactoring Many Methods into One

I dont know how to name the question properly, so fell free to change it. My question is, I have around 10 methods that look like:
[WebMethod(EnableSession = true)]
public string ReadUserAdditional()
{
EUser user = (EUser)Session["user"];
var json = new { result = true, user.Image, user.Biography };
return new JavaScriptSerializer().Serialize(json);
}
[WebMethod(EnableSession = true)]
public string ReadUserBasicInformation()
{
EUser user = (EUser)Session["user"];
var json = new { result = true, user.Name, user.Username};
return new JavaScriptSerializer().Serialize(json);
}
The methods are very similar, but they return different fields. Im thinking about refactoring all methods into one, receveing the fields to return as parameters. Is it a good idea? How can I do that? Reflection?

First of all you need to know that object and dictionary are presented in json simmilar.
[WebMethod(EnableSession = true)]
public string ReadUserAdditional()
{
return GetUserInfo(new []
{
new FieldInfo {Name = "Image", u => u.Image},
new FieldInfo {Name = "Biography", u => u.Biography}
});
}
private string GetUserInfo(FieldInfo[] infos)
{
EUser user = (EUser)Session["user"];
var dict = new Dictionary<string, object>{ { "result", true } };
foreach(var info in infos)
{
dictionary.Add(info.Name, info.Accessor(user));
}
return new JavaScriptSerializer().Serialize(dict );
}
public class FieldInfo
{
public Func<EUser, object> Accessor { get; set; }
public string Name { get; set;}
}

I don't think it's a terrible idea, especially if you have tons of these methods and want to simplify your API.
A few downsides:
1) Reflection comes at a perf cost. This probably doesn't matter a whole lot unless you're the size of Twitter.
2) There would potentially be security concerns if the data had any properties you do NOT wanting users getting access to, such as some sort of internal database keys or what not. Make sure every property on your class is one you're totally okay becoming public information.

You can use a lambda to refactor away the duplication:. This would reduce all your methods to a single line of code:
[WebMethod(EnableSession = true)]
public string ReadUserAdditional()
{
return GetUserJSON(x => new { result = true, x.Image, x.Biography });
}
[WebMethod(EnableSession = true]
public string ReadUserBasicInformation()
{
return GetUserJSON(x => new { result = true, x.Name, x.UserName });
}
private string GetUserJSON(Func<EUser, string> jsonFields)
{
EUser user = (EUser)Session["user"];
var json = jsonFields(user);
return new JavaScriptSerializer().Serialize(json);
}

Another approach is to use Automapper or similar library to project your data.
[WebMethod(EnableSession = true)]
public string ReadUserAdditional()
{
return GetUserInfo<UserAdditionalDto>();
}
private string GetUserInfo<TDto>(FieldInfo[] infos)
{
EUser user = (EUser)Session["user"];
var dto = Mapper.Map<TDto>(user); // Mapper is Automapper entry class.
return new JavaScriptSerializer().Serialize(dto );
}
public class UserAdditionalDto
{
public string Image { get; set; }
public string Biography { get; set;}
}

Writing a Workflow Foundation workflow with C#

I'm trying to write some activities with C# instead of the designer and XAML. VS2010 has been buggy and very slow for that, and it also has very poor compilation support (for variables names, properties and so on).
So I'm trying to create activities by inheriting from the Activity class directly, but I'm encountering a snag.
Here's my code:
public class TestActivity : Activity
{
public InArgument<string> Username { get; set; }
public InArgument<string> Password { get; set; }
public OutArgument<bool> ValidCredential { get; set; }
public OutArgument<ProvisioningRole> Role { get; set; }
public OutArgument<Guid> Guid { get; set; }
protected override Func<Activity> Implementation
{
get
{
return () =>
{
return new Sequence()
{
Activities =
{
new AuthenticateUserActivity()
{
Username = this.Username,
Password = this.Password,
Guid = this.Guid,
Result = this.ValidCredential
},
new If()
{
Condition = this.ValidCredential,
Then = new GetUserRoleActivity()
{
Username = this.Username,
Password = this.Password,
Result = this.Role
}
},
}
};
};
}
set { base.Implementation = value; }
}
}
The problem is with the If(), the condition. It's supposed to be an InArgument, but this.ValidCredential is an OutArgument. I've tried creating a Variable, assign the value of ValidCredential to it. I also tried to put the result of AuthenticateUserActivity in the variable and then assign it to ValidCredential, but I get an error saying the To property of Assign needs to be specified.
I've looked around for proper tutorials, but all I found was an MSDN article that had a quick and dirty code implementation, and it used literals instead of the passed arguments, so no help from there.

I found out how to do it. You just need to create new InArgument from the original one. There is a constructor that takes an expression for it.
Username = new InArgument<bool>((ActivityContext c) => this.ValidCredential.Get(c))
So I changed my whole activity to
return new CompensableActivity()
{
Body = new Sequence()
{
Activities =
{
new AuthenticateUserActivity()
{
Username = this.Username.In(),
Password = this.Password.In(),
Guid = this.Guid.Out(),
Result = this.ValidCredential.Out()
},
new If(this.ValidCredential.In())
{
Then = new GetUserRoleActivity()
{
Username = this.Username.In(),
Password = this.Password.In(),
Result = this.Role.Out()
},
Else = new Assign<ProvisioningRole>()
{
To = this.Role.Out(),
Value = ProvisioningRole.User
}
}
}
},
};
In and Out being extension methods I wrote:
public static class WorkflowExtensions
{
#region In
public static InArgument<T> In<T>(this InArgument<T> self)
{
return new InArgument<T>(context => self.Get(context));
}
public static InArgument<T> In<T>(this OutArgument<T> self)
{
return new InArgument<T>(context => self.Get(context));
}
#endregion
#region Out
public static OutArgument<T> Out<T>(this InArgument<T> self)
{
return new OutArgument<T>(context => self.Get(context));
}
public static OutArgument<T> Out<T>(this OutArgument<T> self)
{
return new OutArgument<T>(context => self.Get(context));
}
#endregion
}
And now all is well!

You should be able to get this to work. The basic approach should be to use a Variable to store data, use an OutArgument to get data out of activities into the Variable and InArguments to get data from a Variable into an activity.
Also note that the expressions to tie InArguments to Variables are VisualBasicValue expressions. So something like:
Condition = new VisualBasicValue("System.DateTime.Now.Hour < 12")
This blog post isn't about using arguments and variables but shows a couple of examples.

Going to shamelessly plug my own library that I ended up making for this:
http://code.google.com/p/system-transactions/
Allows basic compensation of code without the ginormous hassle of WF. Also, compiles properly and is easily debuggable.