MVC4--Model常见问题
添加实体类模型文件
public class Album { public virtual int AlbumId { get; set; } public virtual int GenreId { get; set; } public virtual int ArtistId { get; set; } public virtual string Title { get; set; } public virtual decimal Price { get; set; } public virtual string AlbumArtUrl { get; set; } public virtual Genre Genre { get; set; } public virtual Artist Artist { get; set; } }
public class Artist { public virtual int ArtistId { get; set; } public virtual string Name { get; set; } }
public class Genre { public virtual int GenreId { get; set; } public virtual string Name { get; set; } public virtual string Description { get; set; } public virtual List<Album> Albums { get; set; } }
The DbContext Class
public class MusicStoreDB : DbContext
{
public DbSet<Album> Albums { get; set; }
public DbSet<Genre> Genres { get; set; }
public DbSet<Artist> Artists { get; set; }
}
LINQ语句查询方式
var db = new MusicStoreDB(); var allAlbums = from album in db.Albums orderby album.Title ascending select album;
The StoreManagerController控制器
public class StoreManagerController : Controller { private MusicStoreDB db = new MusicStoreDB(); // // GET: /StoreManager/ public ViewResult Index() { var albums = db.Albums.Include(a => a.Genre).Include(a => a.Artist); return View(albums.ToList()); }
视图VIEW中遍历数据方式
@model IEnumerable<MvcMusicStore.Models.Album> @{ ViewBag.Title = "Index"; } <h2>Index</h2> <p> @Html.ActionLink("Create New", "Create") </p> <table> <tr> <th>@Html.DisplayNameFor(model => model.Genre.Name)</th> <th>@Html.DisplayNameFor(model => model.Artist.Name)</th> <th>@Html.DisplayNameFor(model => model.Title)</th> <th>@Html.DisplayNameFor(model => model.Price)</th> <th>@Html.DisplayNameFor(model => model.AlbumArtUrl)</th> <th></th> </tr> @foreach (var item in Model) { <tr> <td>@Html.DisplayFor(modelItem => item.Genre.Name)</td> <td>@Html.DisplayFor(modelItem => item.Artist.Name)</td> <td>@Html.DisplayFor(modelItem => item.Title)</td> <td>@Html.DisplayFor(modelItem => item.Price)</td> <td>@Html.DisplayFor(modelItem => item.AlbumArtUrl)</td> <td> @Html.ActionLink("Edit", "Edit", new { id=item.AlbumId }) | @Html.ActionLink("Details", "Details", new { id=item.AlbumId }) | @Html.ActionLink("Delete", "Delete", new { id=item.AlbumId }) </td> </tr> } </table>
数据库连接字符串配置
<connectionStrings> <add name="MusicStoreDB" connectionString="data source=.\SQLEXPRESS; Integrated Security=SSPI; initial catalog=MusicStore" providerName="System.Data.SqlClient" /> </connectionStrings>
三步完成数据初始化
1. 实现模型类.
2. 在控制器中用脚手架视图.
3. 选择数据初始化策略。
Using Database Initializers使用数据库初始化
修改global.asax.cs文件
protected void Application_Start() { Database.SetInitializer(new MusicStoreDbInitializer()); AreaRegistration.RegisterAllAreas(); RegisterGlobalFilters(GlobalFilters.Filters); RegisterRoutes(RouteTable.Routes); }
Seeding a Database插入初始数据
public class MusicStoreDbInitializer : DropCreateDatabaseAlways<MusicStoreDB> { protected override void Seed(MusicStoreDB context) { context.Artists.Add(new Artist {Name = "Al Di Meola"}); context.Genres.Add(new Genre { Name = "Jazz" }); context.Albums.Add(new Album { Artist = new Artist { Name="Rush" }, Genre = new Genre { Name="Rock" }, Price = 9.99m, Title = "Caravan" }); base.Seed(context); } }
建立一个资源编辑Album
// // GET: /StoreManager/Edit/8 public ActionResult Edit(int id = 0) { Album album = db.Albums.Find(id); if (album == null) { return HttpNotFound(); } ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId); ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId); return View(album); }
视图页面代码
<div class="editor-field"> @Html.DropDownList("GenreId", String.Empty) @Html.ValidationMessageFor(model => model.GenreId) </div>
模型与视图模型
视图页面中可能需要来自多个Model的信息，因此引入视图Model对页面中需要显示的信息汇总到一个模型中。
public class AlbumEditViewModel { public Album AlbumToEdit { get; set; } public SelectList Genres { get; set; } public SelectList Artists { get; set; } }
The Edit View编辑视图
@using (Html.BeginForm()) { @Html.DropDownList("GenreId", String.Empty) @Html.EditorFor(model => model.Title) @Html.EditorFor(model => model.Price) <p> <input type="submit" value="Save" /> </p> }
解析后的html代码
<form action="/storemanager/Edit/8" method="post"> <select id="GenreId" name="GenreId"> <option value=""></option> <option selected="selected" value="1">Rock</option> <option value="2">Jazz</option> </select> <input class="text-box single-line" id="Title" name="Title" type="text" value="Caravan" /> <input class="text-box single-line" id="Price" name="Price" type="text" value="9.99" /> <p> <input type="submit" value="Save" /> </p> </form>
Responding to the Edit POST Request 用POST选择器属性，执行相应的动作
// // POST: /StoreManager/Edit/8 [HttpPost] public ActionResult Edit(Album album) { if (ModelState.IsValid) { db.Entry(album).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId); ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId); return View(album); }
MODEL BINDING模型绑定
只更新Model中的部分值使用模型绑定的方式
[HttpPost] public ActionResult Edit() { var album = new Album(); album.Title = Request.Form["Title"]; album.Price = Decimal.Parse(Request.Form["Price"]); // ... and so on ... }
Explicit Model Binding显示模型绑定
将页面传入的模型保存在UPdateModel中，出现异常直接返回页面已经选择的值。
[HttpPost] public ActionResult Edit() { var album = new Album(); try { UpdateModel(album); db.Entry(album).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } catch { ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId); ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId); return View(album); } }
TryUpdateModel也调用模型绑定,但是不会抛出异常。TryUpdateModel并返回一个布尔- true值如果模型绑定成功,该模型是有效的,返回真，无效返回false。
[HttpPost] public ActionResult Edit() { var album = new Album(); if (TryUpdateModel(album)) { db.Entry(album).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } else { ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId); ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId); return View(album); } }
验证模型绑定是否成功
[HttpPost] public ActionResult Edit() { var album = new Album(); TryUpdateModel(album); if (ModelState.IsValid) { db.Entry(album).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } else { ViewBag.GenreId = new SelectList(db.Genres, "GenreId", "Name", album.GenreId); ViewBag.ArtistId = new SelectList(db.Artists, "ArtistId", "Name", album.ArtistId); return View(album); }}
