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How MVC populates a model when data is sent back

MVC very clearly describes how data is sent to the browser. You go to the URL, it runs the code to create the model, passes that typed model to the view, which then displays HTML based on the state of the model.

What I don’t detect is so clear when the user submits the form on the page, what does the MVC map look like, which forms the message back to the model for use in the controller?

I guess the magic happens somewhere in:

@Html.EditorFor(model => model.Title)

But I do not understand why ....

I am following Getting started with ASP.NET MVC 3 . Below is the code below for convenience.

Controller:

 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); }

View:

 @model MvcMovie.Models.Movie @{ ViewBag.Title = "Edit"; } <h2>Edit</h2> <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script> @using (Html.BeginForm()) { @Html.ValidationSummary(true) <fieldset> <legend>Movie</legend> @Html.HiddenFor(model => model.ID) <div class="editor-label"> @Html.LabelFor(model => model.Title) </div> <div class="editor-field"> @Html.EditorFor(model => model.Title) @Html.ValidationMessageFor(model => model.Title) </div> <div class="editor-label"> @Html.LabelFor(model => model.ReleaseDate) </div> <div class="editor-field"> @Html.EditorFor(model => model.ReleaseDate) @Html.ValidationMessageFor(model => model.ReleaseDate) </div> <div class="editor-label"> @Html.LabelFor(model => model.Genre) </div> <div class="editor-field"> @Html.EditorFor(model => model.Genre) @Html.ValidationMessageFor(model => model.Genre) </div> <div class="editor-label"> @Html.LabelFor(model => model.Price) </div> <div class="editor-field"> @Html.EditorFor(model => model.Price) @Html.ValidationMessageFor(model => model.Price) </div> <p> <input type="submit" value="Save" /> </p> </fieldset> } <div> @Html.ActionLink("Back to List", "Index") </div>

What generates:

 <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>Edit</title> <link href="/Content/Site.css" rel="stylesheet" type="text/css" /> <script src="/Scripts/jquery-1.5.1.min.js" type="text/javascript"></script> <script src="/Scripts/modernizr-1.7.min.js" type="text/javascript"></script> </head> <body> <div class="page"> <header> <div id="title"> <h1>MVC Movie App</h1> </div> ... </header> <section id="main"> <h2>Edit</h2> <script src="/Scripts/jquery.validate.min.js" type="text/javascript"></script> <script src="/Scripts/jquery.validate.unobtrusive.min.js" type="text/javascript"></script> <form action="/Movies/Edit/4" method="post"> <fieldset> <legend>Movie</legend> <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" /> <div class="editor-label"> <label for="Title">Title</label> </div> <div class="editor-field"> <input class="text-box single-line" id="Title" name="Title" type="text" value="Rio Bravo" /> <span class="field-validation-valid" data-valmsg-for="Title" data-valmsg-replace="true"></span> </div> <div class="editor-label"> <label for="ReleaseDate">ReleaseDate</label> </div> <div class="editor-field"> <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" /> <span class="field-validation-valid" data-valmsg-for="ReleaseDate" data-valmsg-replace="true"></span> </div> <div class="editor-label"> <label for="Genre">Genre</label> </div> <div class="editor-field"> <input class="text-box single-line" id="Genre" name="Genre" type="text" value="Western" /> <span class="field-validation-valid" data-valmsg-for="Genre" data-valmsg-replace="true"></span> </div> <div class="editor-label"> <label for="Price">Price</label> </div> <div class="editor-field"> <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" /> <span class="field-validation-valid" data-valmsg-for="Price" data-valmsg-replace="true"></span> </div> <p> <input type="submit" value="Save" /> </p> </fieldset> </form> <div> <a href="/Movies">Back to List</a> </div> </section> <footer> </footer> </div> </body> </html>
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3 answers

MVC simply maps the public properties of the model to the values ​​in the FormsCollection with the same name. If there is a match with the name and type, then an instance of the model and the values ​​copied to these properties are created.

This process is called model binding, and you can create your own model bindings.

The process has little to do with EditorFor directly, although EditorFor uses templates that must necessarily indicate the inputs of the form in such a way as to understand what the model’s middleware can understand.

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ASP.Net MVC is based on the concept of convention over configuration. Thus, most things work like magic, but under the mechanisms there are functions by default, and also for customization, if you want. The term model binding is a keyword that you must check to understand this.

Check here

6-tips-for-asp-net-mvc-model-binding

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MVC uses what is called Pattern Linking to obtain feedback values ​​and recreate the model.

Here is a good text: Models and validation in ASP.NET MVC

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Source: https://habr.com/ru/post/1392519/

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