ASP.NET MVC TIPS




MODEL binding

public class Album {
    public int AlbumId { get; set; }
    public string Title { get; set; }
    public decimal Price { get; set; }
    public Artist Artist { get; set; }
}

public class Artist {
    public int ArtistId { get; set; }
    public string Name { get; set; }
    public string Country { get; set; }
    public string TwitterHandler { get; set; }
}    
public class AlbumController {
    private IAlbumRepository albumRepo = new AlbumRepository(new DBContext());
    
    public ActionResult Edit(Album album)
    {
         albumRepo.UpdateAlbum(album); //update in database
         albumRepo.Save(); 
         return View(album);   
    }
}

1. Form submission 
<form action="/Album/Edit" method="post">
    <input type="text" name="Title" value="AM" />
    <input type="text" name="Price" value="12" />

    <input type="text" name="Artist.Name" value="Arctic Monkeys" />
    <input type="text" name="Artist.Country" value="Australia" />

    <input type="submit" value="Submit" />
</form>
2. AJAX post
 $.ajax({
  type: 'POST',
  url: 'Album/Edit',
  data: {   Title : 'AM', 
            Price : '12', 
            Artist : { Name : 'Arctic Monkeys', Country : 'Australia' } 
        },
  success: function() {},
  dataType: 'json'
});

public class AlbumController
{
    private IAlbumRepository albumRepo = new AlbumRepository(new DBContext());

    public ActionResult Edit(Album album)
    {
         //album.Title = "AM"
         //album.Price = "12"
         //album.Artist.Name = "Arctic Monkeys";
         //album.Artist.Country = "Australia";

         albumRepo.UpdateAlbum(album); //update into database using EF
         albumRepo.Save();
         return View(album);
    }
}
!Over binding 
<form action="/Album/Edit" method="post">
    <input type="text" name="Title" value="AM" />
    ...
    <input type="text" name="TwitterHandler" value="IAmJackyBlack"/>
    <input type="submit" value="Submit" />
</form>

Fix 1 - bind only required fields to the action

public ActionResult Edit([Bind(Include="Title,Price")] Album album)
{
    ...
}

Fix 2 - don't bind to domain model directly, use view model

public ActionResult Edit(AlbumModel albumModel)
{
    var album = new Album 
                {
                    AlbumId = albumModel.AlbumId,
                    Title = albumModel.Title, 
                    Price = albumModel.Price,
                    ...
                };
    albumRepo.UpdateAlbum(album); //update in database

    return View(album);}




Never trust user input!




controllers

User: Admin - can edit all albums




"Aerosmith - Big Ones"

AlbumId = 2

User: AC/DC Manager - can edit albums of AC/DC




"AC/DC - Let There Be Rock"


AlbumId = 1





public ActionResult Edit(AlbumModel albumModel)
{
    var album = albumRepo.GetAlbum(albumModel.AlbumId);

    album.Price = albumModel.Price; 

    albumRepo.UpdateAlbum(album);
    albumRepo.Save();

    return View(album);
}

!AC/DC Manager can edit all albums by entering the id in the url

 
 http://localhost/StoreManager/Edit/2

Fix 1: Deny access to edit page if album doesn't belong to user

Fix 2: Check if album can be edited by logged in user


[HttpPost]public ActionResult Edit(AlbumModel albumModel)
{
    var album = albumRepo.GetAlbum(albumModel.AlbumId);

    if (SessionHelper.User.CanEditAlbum(album))
    {
        album.Price = albumModel.Price; 

        albumRepo.UpdateAlbum(album);
        albumRepo.Save();

        return View(album);
    }
    else
        return View("NotAllowed");
}




Never trust user input!




entity framework

public class Album
{
    public int AlbumId { get; set; }
    public string Title { get; set; }
    public decimal Price { get; set; }
    public Artist Artist { get; set; }
}


private MusicStoreDB db = new MusicStoreDB();

var albums = db.Albums.ToList();

foreach (var album in albums) {
     Console.WriteLine(album.Artist.Name);
}

!N+1 issue
private MusicStoreDB db = new MusicStoreDB();

var albums = db.Albums.ToList();

SELECT AlbumId, Title, Price, ...
FROM dbo.Albums

 
foreach (var album in albums) {
     Console.WriteLine(album.Artist.Name);
}

SELECT Name, Country, ...
From Artist
WHERE ArtistId = {0}






N + 1 database queries instead of 1 query

Fix 1: Use eager loading vs lazy loading

private MusicStoreDB db = new MusicStoreDB();

var albums = db.Albums.Include(a => a.Artist).ToList();

foreach (var album in albums) {
     Console.WriteLine(album.Artist.Name);
}

Fix 2: Request only required fields


a. Extended syntax

private MusicStoreDB db = new MusicStoreDB();

var albums =
(
     from   album in db.Albums
     select new AlbumModel
            {
                AlbumId = album.AlbumId,
                Title = album.Title,
                ...
                ArtistName = album.Artist.Name
            }
);

foreach (var album in albums) {
     Console.WriteLine(album.ArtistName);
}

b. Compact syntax

private MusicStoreDB db = new MusicStoreDB();

var albums = db.Albums.Select
             (
                  album => new AlbumModel
                  {
                      AlbumId = album.AlbumId,
                      Title = album.Title,
                      ...
                      ArtistName = album.Artist.Name
                  }
             );
);

foreach (var album in albums) {
     Console.WriteLine(album.ArtistName);
}



Check DB queries generated by entity framework



MVC Music Store



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ASP.NET MVC TIPS

By Yhoan Andres Galeano Urrea

Source: Szilard David

ASP.NET MVC TIPS

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