Introduction to MVC Action Methods, Edit View, and a Search Feature NTPCUG Dr. Tom Perkins

The Edit Link Run the application Append /Movies to the URL (browse to the Movies controller) Hover over the Edit link Examine the generated URL

The Edit link was generated by the Html.ActionLink method in the Views\Movies\Index.cshtml "Edit", new { id=item.ID }) Hover

The ActionLink HtmlHelper Generates a link to an action method on a controller Arguments: – 1) Text to render (Edit Me) – 2) Name of action method in controller (Edit) – 3) anonymous object  route data (ID=4)

Alternative: Pass Parameters Using Query String URL of: Request sent to Controller: Movies Action Method: Edit Parameter ID: 4

2 Edit Actions in the Movies Controller // // GET: /Movies/Edit/5 public ActionResult Edit(int id = 0) { Movie movie = db.Movies.Find(id); if (movie == null) { return HttpNotFound(); } return View(movie); } // // POST: /Movies/Edit/5 [HttpPost] public ActionResult Edit(Movie movie) { if (ModelState.IsValid) { db.Entry(movie).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } return View(movie); } HttpPost Attribute Invoked ONLY for POST requests Default: Implied [HttpGet] attribute Invoked for GET requests

The HTTPGet Edit Method 1. movie ID paramter input (default = 0) 2.Entity Framework Find used to look up the movie 3.If movie cant be found, return HttpNotFound() 4.The Model movie object is passed to the view When the Edit View was created, the system scanned the model and generated the markup to edit the fields. // // GET: /Movies/Edit/5 public ActionResult Edit(int id = 0) { Movie movie = db.Movies.Find(id); if (movie == null) { return HttpNotFound(); } return View(movie); }

The Generated Edit View (Part ViewBag.Title = "Edit"; } Edit The View expects that the Model it receives will be of type Movie

The Generated Edit View (Part (Html.BeginForm()) => => => => model.Title) … LabelFor displays the name of the field HtmlEditorFor renders an statement ValidationMessageFor displays validation messages associated with field

Run the Application Navigate to /Movies URL Click an Edit link View the source for the page Examine the HTML for the Form element Note: Html elements are in a element Form action attribute is set to post When Edit button is clicked, data will be posted to the server

Server actions when the Save button is clicked and the data is posted: The values from the Form are transformed into a Movie object by the ASP MVC model binder. The Movie object is passed to the Edit action in the Movies controller. The ModelState.IsValid method determines whether or not the data submitted in the form is OK, the data is saved in the db MovieDBContext instance. The movie data is saved to the database. The user is redirected to the Index action, which displays the data with changes. If form data is invalid, data is re- displayed with error messages created by Html.ValidationMessageFor helpers. [HttpPost] public ActionResult Edit(Movie movie) { if (ModelState.IsValid) { db.Entry(movie).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } return View(movie); }

Posting Edited Form Data Form Edited Data ModelState.IsValid method Valid data Data saved to database Data sent to Index action, data (including changes) is displayed Invalid data sent back to form with error messages and form is redisplayed.

Validation error messages

Add a Search Method and View Objective: allow the user to search for movies by genre or name Add a SearchIndex action to the controller SearchAction method generates Html form for user to enter genre or name Get Search Values Search Database Display Results User submits search criteria

Add a SearchIndex method to the MoviesController class s => s.Title is a Lambda expression Used in LINQ queries LINQ queries not executed when defined or modified (deferred) Executed when value is used or in ToList() Execution takes place in View public ActionResult SearchIndex(string searchString) { var movies = from m in db.Movies select m; if (!String.IsNullOrEmpty(searchString)) { movies = movies.Where(s => s.Title.Contains(searchString)); } return View(movies); }

Display the Search form for the User Create a SearchIndex View: Right click inside the SearchIndex Method In the AddView dialog box: – Pass a Movie object to the view – Choose List in the Scaffold Template – Click Add

The Create ViewBag.Title = "SearchIndex"; } New", "Create") Title ReleaseDate Genre (var item in Model) => => => => "Edit", new { id=item.ID }) "Details", new { id=item.ID }) "Delete", new { id=item.ID }) }

Run the App Navigate using /Movies/SearchIndex?searchString=ghost

Add a ViewBag.Title = "SearchIndex"; } New", (Html.BeginForm()){ }

FINIS