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POHow does MVC populate the model when data is posted back
 

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  1. POHow does MVC populate the model when data is posted back
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    <p>MVC is very clear on how data is sent to the browser. You go to a URL, it runs code to create a model, passes that typed model into a view, which then renders HTML based on the state of the model.</p> <p>What I'm not finding so clear however is when a user submits a form on the page, how does MVC map that form post back to the model for use in the controller?</p> <p>I'm guessing the magic happens somewhere in:</p> <pre><code>@Html.EditorFor(model =&gt; model.Title) </code></pre> <p>But I'm not understanding why....</p> <p>I'm following <a href="http://www.asp.net/mvc/overview/getting-started" rel="nofollow">Getting started with ASP.NET MVC 3</a>. Which is where the code below is from for easy reference.</p> <p><strong>Controller:</strong></p> <pre><code>public ActionResult Edit(int id) { Movie movie = db.Movies.Find(id); return View(movie); } [HttpPost] public ActionResult Edit(Movie movie) { if (ModelState.IsValid) { db.Entry(movie).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } return View(movie); } </code></pre> <p><strong>View:</strong></p> <pre><code>@model MvcMovie.Models.Movie @{ ViewBag.Title = "Edit"; } &lt;h2&gt;Edit&lt;/h2&gt; &lt;script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"&gt;&lt;/script&gt; &lt;script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"&gt;&lt;/script&gt; @using (Html.BeginForm()) { @Html.ValidationSummary(true) &lt;fieldset&gt; &lt;legend&gt;Movie&lt;/legend&gt; @Html.HiddenFor(model =&gt; model.ID) &lt;div class="editor-label"&gt; @Html.LabelFor(model =&gt; model.Title) &lt;/div&gt; &lt;div class="editor-field"&gt; @Html.EditorFor(model =&gt; model.Title) @Html.ValidationMessageFor(model =&gt; model.Title) &lt;/div&gt; &lt;div class="editor-label"&gt; @Html.LabelFor(model =&gt; model.ReleaseDate) &lt;/div&gt; &lt;div class="editor-field"&gt; @Html.EditorFor(model =&gt; model.ReleaseDate) @Html.ValidationMessageFor(model =&gt; model.ReleaseDate) &lt;/div&gt; &lt;div class="editor-label"&gt; @Html.LabelFor(model =&gt; model.Genre) &lt;/div&gt; &lt;div class="editor-field"&gt; @Html.EditorFor(model =&gt; model.Genre) @Html.ValidationMessageFor(model =&gt; model.Genre) &lt;/div&gt; &lt;div class="editor-label"&gt; @Html.LabelFor(model =&gt; model.Price) &lt;/div&gt; &lt;div class="editor-field"&gt; @Html.EditorFor(model =&gt; model.Price) @Html.ValidationMessageFor(model =&gt; model.Price) &lt;/div&gt; &lt;p&gt; &lt;input type="submit" value="Save" /&gt; &lt;/p&gt; &lt;/fieldset&gt; } &lt;div&gt; @Html.ActionLink("Back to List", "Index") &lt;/div&gt; </code></pre> <p><strong>Which generates:</strong></p> <pre><code>&lt;!DOCTYPE html&gt; &lt;html&gt; &lt;head&gt; &lt;meta charset="utf-8" /&gt; &lt;title&gt;Edit&lt;/title&gt; &lt;link href="/Content/Site.css" rel="stylesheet" type="text/css" /&gt; &lt;script src="/Scripts/jquery-1.5.1.min.js" type="text/javascript"&gt;&lt;/script&gt; &lt;script src="/Scripts/modernizr-1.7.min.js" type="text/javascript"&gt;&lt;/script&gt; &lt;/head&gt; &lt;body&gt; &lt;div class="page"&gt; &lt;header&gt; &lt;div id="title"&gt; &lt;h1&gt;MVC Movie App&lt;/h1&gt; &lt;/div&gt; ... &lt;/header&gt; &lt;section id="main"&gt; &lt;h2&gt;Edit&lt;/h2&gt; &lt;script src="/Scripts/jquery.validate.min.js" type="text/javascript"&gt;&lt;/script&gt; &lt;script src="/Scripts/jquery.validate.unobtrusive.min.js" type="text/javascript"&gt;&lt;/script&gt; &lt;form action="/Movies/Edit/4" method="post"&gt; &lt;fieldset&gt; &lt;legend&gt;Movie&lt;/legend&gt; &lt;input data-val="true" data-val-number="The field ID must be a number." data-val-required="The ID field is required." id="ID" name="ID" type="hidden" value="4" /&gt; &lt;div class="editor-label"&gt; &lt;label for="Title"&gt;Title&lt;/label&gt; &lt;/div&gt; &lt;div class="editor-field"&gt; &lt;input class="text-box single-line" id="Title" name="Title" type="text" value="Rio Bravo" /&gt; &lt;span class="field-validation-valid" data-valmsg-for="Title" data-valmsg-replace="true"&gt;&lt;/span&gt; &lt;/div&gt; &lt;div class="editor-label"&gt; &lt;label for="ReleaseDate"&gt;ReleaseDate&lt;/label&gt; &lt;/div&gt; &lt;div class="editor-field"&gt; &lt;input class="text-box single-line" data-val="true" data-val-required="The ReleaseDate field is required." id="ReleaseDate" name="ReleaseDate" type="text" value="4/15/1959 12:00:00 AM" /&gt; &lt;span class="field-validation-valid" data-valmsg-for="ReleaseDate" data-valmsg-replace="true"&gt;&lt;/span&gt; &lt;/div&gt; &lt;div class="editor-label"&gt; &lt;label for="Genre"&gt;Genre&lt;/label&gt; &lt;/div&gt; &lt;div class="editor-field"&gt; &lt;input class="text-box single-line" id="Genre" name="Genre" type="text" value="Western" /&gt; &lt;span class="field-validation-valid" data-valmsg-for="Genre" data-valmsg-replace="true"&gt;&lt;/span&gt; &lt;/div&gt; &lt;div class="editor-label"&gt; &lt;label for="Price"&gt;Price&lt;/label&gt; &lt;/div&gt; &lt;div class="editor-field"&gt; &lt;input class="text-box single-line" data-val="true" data-val-number="The field Price must be a number." data-val-required="The Price field is required." id="Price" name="Price" type="text" value="9.99" /&gt; &lt;span class="field-validation-valid" data-valmsg-for="Price" data-valmsg-replace="true"&gt;&lt;/span&gt; &lt;/div&gt; &lt;p&gt; &lt;input type="submit" value="Save" /&gt; &lt;/p&gt; &lt;/fieldset&gt; &lt;/form&gt; &lt;div&gt; &lt;a href="/Movies"&gt;Back to List&lt;/a&gt; &lt;/div&gt; &lt;/section&gt; &lt;footer&gt; &lt;/footer&gt; &lt;/div&gt; &lt;/body&gt; &lt;/html&gt; </code></pre>
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