problem in getting Value from Json Key Value Pair

Question

I am following this link to build a Client side repeater.

According to the above link to retrive the value from a Json key-value pair we can use result[i].property,for example

for (var post in msg)
{     
    var x= msg[post].Date;
    alert(x);
}

Here x returns the date from Json string. When I am trying to use the same with my data, it always returns as undefined. I tried to pop up an alert(msg.d) that shows a nice Json string with all my data. But when I try msg[post].Date(property name) it's always returning undefined.

Please help..

Thanks in advance.

Update:

From the backend I am returning a generic list and then converting it into Json using the following code.

public static string ConvertToJSON(this object obj) {

    DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());    

    MemoryStream ms = new MemoryStream();
    serializer.WriteObject(ms, obj);
    string jsonobj = Encoding.Default.GetString(ms.ToArray());
    ms.Dispose();
    return jsonobj;
}

then I am appending the returned Json to a stringbuilder and returning it to the Jquery ajax method.The returned Json looks like a string , not an object and hence I am unable to get any value from Json key value pair..

get firebug, place a breakpoint and look at the different values in the watch window. Check what is in post, msg[post]. — Vinodh Ramasubramanian
– Vinodh Ramasubramanian, Commented Feb 4, 2010 at 17:15
Hi Patrick, following is a sample of what is returned when I do alert(msg.d) [{"AnsNo":0,"Answer":"","Category":"Help Centre.Mortgages.Existing customers","ClickURL":null,"ID":7,"Question":"How do I re-mortgage to you?","RecNo":0,"ValidFrom":"\/Date(-62135596800000+0000)\/","ValidUntill":"\/Date(-62135596800000+0000)\/"}] so I am trying with msg[post].AnsNo ,msg[post].Answer, msg[post].Category etc — kranthi
– kranthi, Commented Feb 4, 2010 at 17:17
I don't understand what this piece of code is trying to do: msg[post].Date(property name). It appears that it will set the Date using property name which is not a date object, but aren't you trying to read the date? Could you post more of your code please — Mottie
– Mottie, Commented Feb 4, 2010 at 17:43
You've asked 8 questions and selected 0 answers. Fix that first and then I will help you. — Josh Stodola
– Josh Stodola, Commented Feb 4, 2010 at 17:49

Dave Ward · Accepted Answer · 2010-02-05 17:43:12Z

1

Update:

It sounds like you're doubly serializing the data on the server-side, returning a JSON string that gets serialized as JSON itself. When that reaches the client-side and jQuery deserializes the first layer of JSON automatically, you're still left with the JSON string you manually built.

You should return the List<T> as the return value of your service method and let the framework handle JSON serialization.

Original Answer:

Assuming the object is still contained in ASP.NET AJAX's ".d" wrapper, as you implied:

for (var post in msg.d) {     
  var x = msg.d[post].Date;

  alert(x);
}

Or, a traditional loop, which might be more straightforward:

for (var i = 0; i < msg.d.length; i++) {
  var x = msg.d[i].Date;

  alert(x);
}

edited Feb 5, 2010 at 17:43

answered Feb 4, 2010 at 19:07

Dave Ward

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7 Comments

kranthi Over a year ago

Thanks Dave,after reading your post I realized that I am double serializing the data.such a silly mistake.Now I'm able to read the value with msg.d[0].Date.But got another problem.basically in the code behind web method I have different conditions.Based on the condition different generic list(ex.faqs,recognitions etc) is returned to the Jquery ajax method.I do not understand how can I set the return type(generic list) for the Web method based on the condition using your solution.Previously I used to append the string returned from Converttojson to a stringbuilder and return.

Dave Ward Over a year ago

Use IEnumerable as the return type.

kranthi Over a year ago

Returning IEnumerable looks like a great idea.In my code I have some conditions which will have to retrive data from multiple generic lists.For example if a condition is satisfied I need to do the following. Recognitionfactory rf = new Recognitionfactory(); Recognitions rs= rf.getBasicSearchRecognitions(searchtext); Answerfactory af = new Answerfactory(); Answers ans = af.getBasicSearchAnswers(searchtext); In the above case I need to return both rs,ans(generic lists) upon satisfying a certain condition.how can I return both of them for one condition?

kranthi Over a year ago

Ofcourse,It is possible to return either ans or rs with ienumerable being the return type of the web method.how to handle returning both ans,rs

Dave Ward Over a year ago

An IEnumerable could contain a collection of IEnumerables. That sounds like it's going to be difficult to work with though. Are you sure you shouldn't refactor it into separate methods? Or, maybe use a common DTO class (e.g. SearchResults) and map the various possible results to a List<SearchResults>?

|

Mickael Lherminez · Accepted Answer · 2019-12-31 08:49:47Z

1

What about the message, if you add this to your ajax does that help?

dataFilter: function(data) {
  var msg;
  if (typeof(JSON) !== 'undefined' &&
    typeof(JSON.parse) === 'function')
    msg = JSON.parse(data);
  else
    msg = eval('(' + data + ')');
  if (msg.hasOwnProperty('d'))
    return msg.d;
  else
    return msg;
},

Note that you then process this as msg, not msg.d like so:

success: function(msg) {
  SaveSuccess(msg);
},

edited Dec 31, 2019 at 8:49

Mickael Lherminez

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answered Feb 4, 2010 at 17:42

Mark Schultheiss

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Comments

Kristoffer Sall-Storgaard · Accepted Answer · 2010-02-04 18:05:56Z

0

Looks to me like you got an array of objects to begin with, using your sample the following works:

messages = [{"AnsNo":0,"Answer":"","Category":"Help Centre.Mortgages.Existing customers","ClickURL":null,"ID":7,"Question":"How do I re-mortgage to you?","RecNo":0,"ValidFrom":"\/Date(-62135596800000+0000)\/","ValidUntill":"\/Date(-62135596800000+0000)\/"}]

for(i in messages)
{
    message = messages[i];
    //Says "Help Centre.Mortgages.Existing customers"
    alert(message.Category)
    //To get all key/value pairs
    for(key in message)
    {
        //Alerts all key value pairs one by one
        alert("Key:" + key + ", Value:" + message[key]);
    }
}

answered Feb 4, 2010 at 18:05

Kristoffer Sall-Storgaard

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