06. Action Methods, Edit View, and a Search Feature

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Introduction to MVC 4
06. 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
Hover
The Edit link was generated by the Html.ActionLink method in the
Views\Movies\Index.cshtml view:
@Html.ActionLink("Edit", "Edit", new { id=item.ID })
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: http://localhost:xxxxx/Movies/Edit?ID=4
Request sent to
Controller: Movies
Action Method: Edit
Parameter ID: 4
//
// 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
Attribute
Default:
Implied
[HttpGet]
attribute
[HttpPost]
public ActionResult Edit(Movie movie)
{
if (ModelState.IsValid)
{
db.Entry(movie).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
return View(movie);
}
2 Edit Actions in the
Movies Controller
Invoked for GET requests
Invoked ONLY for POST requests
The HTTPGet Edit Method
//
// GET: /Movies/Edit/5
public ActionResult Edit(int id = 0)
{
Movie movie = db.Movies.Find(id);
if (movie == null)
{
return HttpNotFound();
}
return View(movie);
}
1.
2.
3.
4.
movie ID paramter input (default = 0)
Entity Framework Find used to look up the movie
If movie cant be found, return HttpNotFound()
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.
The Generated Edit View (Part 1)
@model MvcMovie.Models.Movie
@{
ViewBag.Title = "Edit";
}
<h2>Edit</h2>
The View expects that the Model it
receives will be of type Movie
The Generated Edit View (Part 2)
@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>
…
LabelFor displays the name of the field
HtmlEditorFor renders an <input> 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 <input> elements are in a <form>
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:
[HttpPost]
public ActionResult Edit(Movie movie)
{
if (ModelState.IsValid)
{
db.Entry(movie).State =
EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
return View(movie);
}
•
•
•
•
•
•
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 redisplayed with error messages created
by Html.ValidationMessageFor helpers.
Posting Edited Form Data
Form
Edited Data
ModelState.IsValid
method
Valid
data
Invalid data sent
back to form with
error messages
and form is
redisplayed.
Data saved to
database
Data sent to Index action, data
(including changes) is
displayed
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
User submits search criteria
Search
Database
Display
Results
Add a SearchIndex method to the
MoviesController class
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);
}
• 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
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
@model IEnumerable<MvcMovie.Models.Movie>
@{
ViewBag.Title = "SearchIndex";
}
<h2>SearchIndex</h2>
<p>
@Html.ActionLink("Create New", "Create")
</p>
<table>
<tr>
<th>
Title
</th>
<th>
ReleaseDate
</th>
<th>
Genre
</th>
<th>
Price
</th>
<th></th>
</tr>
The Create View
@foreach (var item in Model) {
<tr>
<td>
@Html.DisplayFor(modelItem => item.Title)
</td>
<td>
@Html.DisplayFor(modelItem => item.ReleaseDate)
</td>
<td>
@Html.DisplayFor(modelItem => item.Genre)
</td>
<td>
@Html.DisplayFor(modelItem => item.Price)
</td>
<td>
@Html.ActionLink("Edit", "Edit", new { id=item.ID }) |
@Html.ActionLink("Details", "Details", new {
id=item.ID }) |
@Html.ActionLink("Delete", "Delete", new {
id=item.ID })
</td>
</tr>
}
</table>
Run the App
• Navigate using
/Movies/SearchIndex?searchString=ghost
Add a filter <form>
@model
IEnumerable<MvcMovie.Models.Movie>
@{
ViewBag.Title = "SearchIndex";
}
<h2>SearchIndex</h2>
<p>
@Html.ActionLink("Create New", "Create")
@using (Html.BeginForm()){
<p> Title:
@Html.TextBox("SearchString")
<br />
<input type="submit"
value="Filter" /></p>
}
</p>
FINIS

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