How to convert View Model into JSON object in ASP NET MVC

Question

I am a Java developer  new to  NET  I am working on a  NET MVC2 project where I want to have a partial view to wrap a widget  Each JavaScript widget object has a JSON data object that would be populated by the model data  Then methods to update this data are bound to events when data is changed in the widget or if that data is changed in another widget   The code is something like this   MyController   virtual public ActionResult DisplaySomeWidget int id      SomeModelView returnData   someDataMapper getbyid 1      return View myview  returnData       myview ascx    lt    Control Language  C   Inherits  System Web Mvc ViewUserControl lt SomeModelView gt     gt    lt script type  text javascript  gt      creates base widget object    var thisWidgetName   new Widget       thisWidgetName updateTable   function             UpdatesData          document  ready function          thisWidgetName data    lt   converttoJSON model    gt        document  bind  DATA CHANGED   thisWidgetName updateTable            lt  script gt    lt div gt  lt   model name  gt  lt  div gt    What I don   t know is how to send the data over as SomeModelView and then be able to use that to populate the widget as well as convert that to JSON  I had seen some real simple ways to do it in the controller but not in the view  I figure this is a basic question but I   ve been going for a few hours trying to make this slick

User · Answer

I found it to be pretty nice to do it like this (usage in the view):

    @Html.HiddenJsonFor(m => m.TrackingTypes)

Here is the according helper method Extension class:

public static class DataHelpers
{
    public static MvcHtmlString HiddenJsonFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
    {
        return HiddenJsonFor(htmlHelper, expression, (IDictionary<string, object>) null);
    }

    public static MvcHtmlString HiddenJsonFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes)
    {
        return HiddenJsonFor(htmlHelper, expression, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
    }

    public static MvcHtmlString HiddenJsonFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IDictionary<string, object> htmlAttributes)
    {
        var name = ExpressionHelper.GetExpressionText(expression);
        var metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);

        var tagBuilder = new TagBuilder("input");
        tagBuilder.MergeAttributes(htmlAttributes);
        tagBuilder.MergeAttribute("name", name);
        tagBuilder.MergeAttribute("type", "hidden");

        var json = JsonConvert.SerializeObject(metadata.Model);

        tagBuilder.MergeAttribute("value", json);

        return MvcHtmlString.Create(tagBuilder.ToString());
    }
}

It is not super-sofisticated, but it solves the problem of where to put it (in Controller or in view?) The answer is obviously: neither ;)

User · Answer

Andrew had a great response but I wanted to tweek it a little  The way this is different is that I like my ModelViews to not have overhead data in them  Just the data for the object   It seem that ViewData fits the bill for over head data  but of course I m new at this  I suggest doing something like this   Controller  virtual public ActionResult DisplaySomeWidget int id        SomeModelView returnData   someDataMapper getbyid 1       var serializer   new JavaScriptSerializer        ViewData  JSON     serializer Serialize returnData       return View myview  returnData       View    create base js object  var myWidget  new Widget      Widget is a class with a public member variable called data  myWidget data   lt    ViewData  JSON     gt     What This does for you is it gives you the same data in your JSON as in your ModelView so you can potentially return the JSON back to your controller and it would have all the parts   This is similar to just requesting it via a JSONRequest however it requires one less call so it saves you that overhead   BTW this is funky for Dates but that seems like another thread

User · Answer

In mvc3 with razor  Html Raw Json Encode object   seems to do the trick

User · Answer

lt htmltag id    elementId    data-ZZZZ        Html Raw Json Encode Model        gt    Refer https   highspeedlowdrag wordpress com 2014 08 23 mvc-data-to-jquery-data   I did  below and it works like charm    lt input id  hdnElement  class  hdnElement  type  hidden  value   Html Raw Json Encode Model    gt

User · Answer

Html Raw Json Encode object   can be used to convert the View Modal Object to JSON

User · Answer

You can use Json from the action directly   Your action would be something like this   virtual public JsonResult DisplaySomeWidget int id        SomeModelView returnData   someDataMapper getbyid id       return Json returnData       Edit  Just saw that you assume this is the Model of a View so the above isn t strictly correct  you would have to make an Ajax call to the controller method to get this  the ascx would not then have a model per se  I will leave my code in just in case it is useful to you and you can amend the call  Edit 2 just put id into the code

User · Answer

Well done  you ve only just started using MVC and you ve found its first major flaw   You don t really want to be converting it to JSON in the view  and you don t really want to convert it in the controller  as neither of these locations make sense  Unfortunately  you re stuck with this situation   The best thing I ve found to do is send the JSON to the view in a ViewModel  like this   var data   somedata  var viewModel   new ViewModel    var serializer   new JavaScriptSerializer    viewModel JsonData   serializer Serialize data    return View  viewname   viewModel     then use   lt    Model JsonData   gt    in your view  Be aware that the standard  NET JavaScriptSerializer is pretty crap   doing it in the controller at least makes it testable  although not exactly like the above - you probably want to take an ISerializer as a dependency so you can mock it   Update also  regarding your JavaScript  it would be good practice to wrap ALL the widget JS you have above like so            all js here        this way if you put multiple widgets on a page  you won t get conflicts  unless you need to access the methods from elsewhere in the page  but in that case you should be registering the widget with some widget framework anyway   It may not be a problem now  but it would be good practice to add the brackets now to save yourself muchos effort in the future when it becomes a requirement  it s also good OO practice to encapsulate the functionality

User · Answer

Extending the great answer from Dave  You can create a simple HtmlHelper   public static IHtmlString RenderAsJson this HtmlHelper helper  object model        return helper Raw Json Encode model        And in your view    Html RenderAsJson Model    This way you can centralize the logic for creating the JSON if you  for some reason  would like to change the logic later

[.net] How to convert View Model into JSON object in ASP.NET MVC?

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