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POASP.NET MVC 5 Html.HiddenFor renders incorrect property value but Model.Property renders correct value
 

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  1. POASP.NET MVC 5 Html.HiddenFor renders incorrect property value but Model.Property renders correct value
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    <ul> <li>Visual Studio 2013 Professional</li> <li>C#</li> <li>.NET 4.5 Framework</li> <li>ASP.NET MVC 5</li> </ul> <p>In my view-model class, I have a property called <code>SerializedSelf</code> that is used to represent itself as a serialized string and also de-serialize, but only over any properties that aren't already initialized. I use this to simplify the round-tripping of my view-model by having a single hidden input with this value. Any other inputs related to the model will get populated in the model by the framework before getting passed to the controller method.</p> <p>The problem I'm having is that in my razor view code this isn't rendering properly:</p> <pre><code> @Html.HiddenFor(model =&gt; model.SerializedSelf) </code></pre> <p>I haven't determined if it's serializing a completely uninitialized <code>MyViewModel</code> object or if it's an instance from somewhere else.</p> <p>But this works properly:</p> <pre><code> &lt;input type="hidden" name="SerializedSelf" id="SerializedSelf" value="@Model.SerializedSelf" /&gt; </code></pre> <p>So I'm guessing it might have something to do with the lambda expression and enclosures??? When I step through in source code, the <code>SerializedSelf</code> has the proper value right before I call <code>return View("myView", model)</code>.</p> <p>Here is the view-model code:</p> <pre><code>using Newtonsoft.Json; using System; using System.Text; public class MyViewModel { [JsonIgnore] public string SerializedSelf { get { return JsonConvert.SerializeObject(this); } set { if (string.IsNullOrWhiteSpace(value)) return; string json = value; MyViewModel copy = JsonConvert.DeserializeObject&lt;MyViewModel&gt;(json); if (Message == null) Message = copy.Message; if (Phone == null) Phone = copy.Phone; // ... } } public string Message { get; set; } public string Phone { get; set; } // ... } </code></pre> <p>What would be the difference between:</p> <pre><code>@Html.HiddenFor(model =&gt; model.SerializedSelf) </code></pre> <p>and</p> <pre><code>@Model.SerializedSelf </code></pre> <p>and what would cause the former to be inaccurate?</p> <p><em>UPDATE 2013/12/5:</em> I removed the logic from <code>SerializedSelf</code> and explicitly serialize/deserialize to/from <code>SerializedSelf</code> at the appropriate times to test if this has any impact. It has no impact and the behavior is as I have described above.</p> <p><em>UPDATE 2013/12/5:</em> Removed HTML encoding and decoding. Was left over from previous attempt at problem solving.</p> <p><em>UPDATE 2013/12/5:</em> I don't have time to look into this today, but it occurred to me that perhaps the <code>[JsonIgnore]</code> attribute on the <code>SerializedSelf</code> property is the culprit and it's interfering with something in the MVC framework. Will look into as soon as I can and update.</p>
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    1. COFirst problem your model contains logic. All logic should be in your controller. [Seperation of conerns](http://en.wikipedia.org/wiki/Separation_of_concerns). I reckon if you get this right your problem will go away.
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      1. USLiam
    2. CO@Liam, my model is specifically a view-model that is only used by the controller, and the logic is probably a gray area for separation of concerns. Regardless, it doesn't explain _why_ I am getting the behavior I am seeing. Property getters are simply specialized method calls and whether it's an auto-property, an explicitly field backed property, or a few lines of code with logic, it shouldn't be rendered differently in the two examples I gave. For completeness, I am converting SerializedSelf to an auto-property and doing the serialization/deserialization explicitly and see if this helps.
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      1. USMikeJansen
    3. CO@Liam, removing the logic from `SerializedSelf` and converting it to an auto-property still results in the same behavior. If put in the `HiddenFor` I get the wrong result. If I explicitly code the hidden input and use `Model.SerializedSelf` I get the correct result. Literally no other changes in the code. It makes no sense. I am likely going to look into the MVC 5 source code and see what `HiddenFor` is doing.
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      1. USMikeJansen
 

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