【譯】MVC3 20個秘方-（18）Auto Complete（自動完成）
問題
當你查找一些特殊的東西，當你輸入準確的詞時，找到它可能是困難的（或者很耗時）。在輸入的時候展示出結果（自動完成），使查找變得更簡單。
解決方案
使用JQuery自動完成插件，更新現有圖書列表頁面上的搜索，當用戶鍵入的時候立即顯示結果。
討論
自動完成插件是不會象jQuery基本庫一樣自動包含在MVC項目中的，所以需要做的第一件事就是的是下載插件
訪問http://jquery.com/。兩個主要的文件是必需的：JavaScript文件和CSS文件。把新下載的javascript文件放到你MVC應用程序的script 文件夾下。CSS文件可以直接添加到您的content目錄。
這個配方也將介紹在view中使用 rendering sections。在shared文件夾下layout中自動添加了2個javascript文件和1個css文件。這些是Ajax和不唐突的Ajax和網站主css文件。每次加載的內容越多，頁面視圖加載越慢。與其在每個頁面都去包含可能不必要的javascript和css 文件，不如在layout中添加一個新的RenderSection()。這允許特別的view在<head>標簽去加載特別的javascript或css，但不是每頁都添加他們。
下邊是一個更新后的Views/Shared/_Layout.cshtml，他使用了一個新的RenderSection（）。
<!DOCTYPE html>
<html>
<head>
<title>_Mobile</title>
<link href="@Url.Content("~/Content/Site.css")" rel="stylesheet" type="text/css" />
<script src="@Url.Content("~/Scripts/jquery-1.6.2.min.js")" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function () {
if (window.innerWidth <= 480) {
$("link[rel=stylesheet]").attr({ href: "@Url.Content("~/Content/jquery.mobile-1.0b1.min.css")" });
}
});
</script>
@RenderSection("JavaScriptAndCSS", required: false)
</head>
<body>
<div class="page" data-role="page">
<div id="header" data-role="header">
<div id="title">
<h1>My MVC Application</h1>
</div>
<div id="logindisplay" class="ui-bar">
@Html.Partial("_LogOnPartial")
[ @Html.ActionLink("English", "ChangeLanguage", "Home", new { language = "en" }, null) ]
[ @Html.ActionLink("Fran?ais", "ChangeLanguage", "Home", new { language = "fr" }, null) ]
</div>
<div id="menucontainer" class="ui-bar">
<ul id="menu">
<li>@Html.ActionLink("Home", "Index", "Home", null, new Dictionary<string, object> {{ "data-role", "button" }})</li>
<li>@Html.ActionLink("About", "About", "Home", null, new Dictionary<string, object> { { "data-role", "button" }})</li>
</ul>
</div>
</div>
<div id="main" data-role="content">
@RenderBody()
</div>
<div id="footer" data-role="footer">
</div>
</div>
</body>
</html>
主要的CSS文件和核心的JQuery文件被留下來了，因為css在每個也都需要，并且絕大多數網頁也需要JQuery。然而新的JQuery文件和不唐突的AJAX不是每個頁面都需要的。
現在，有兩種方式使用Autocomplete 插件：
- 在javascript中設置要搜索的數據。
- 當用戶輸入時通過ajax檢索。
在我使用這個插件的經驗看來，我發現使用解決方案1時自動完成更快。因為它并不需要每次從數據庫中請求數據。然而，使用這種解決方案的限制：只有這么多字符，可傳遞到function中，大量的JavaScript可能會導致
用戶的計算機上頁面加載緩慢。經過一些試驗和錯誤，我已經確定神奇的數字是大約40,000個結果。如果結果數量超過此，最好使用選項2;否則，始終堅持，因為搜索選項1是瞬時，而不是有輕微的延遲。
在這個例子中，將搜索書籍，我們沒有超過40000，所以將使用選項1。BooksController現在必須更新，以設置ViewBag為book title。自動完成功能需要支持一個JavaScript數組的支持，所以書將管道（|）分開。然后在view中，書將被轉換到一個數組，使用JavaScript的split（）函數。當用戶完成鍵入他們的結果，他們應該有選擇完全匹配標題，因此
這個函數將被更新。如果只有1本書返回并且用戶執行了搜索，它會自動重定向到本書詳細介紹頁面。
我們要在bookcontroller 中更新Index Action 并添加一個私有方法名為：FormatBooksForAutocomplete。
代碼如下：
展開查看代碼
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Linq.Dynamic;
using System.Web;
using System.Web.Mvc;
using MvcApplication.Models;
using MvcApplication.Utils;
using PagedList;
namespace MvcApplication.Controllers
{
public class BooksController : Controller
{
private BookDBContext db = new BookDBContext();
//
// GET: /Books/
[OutputCache(Duration = Int32.MaxValue, SqlDependency = "MvcApplication.Models.BookDBContext:books", VaryByParam = "sortOrder;filter;page")]
public ActionResult Index(string sortOrder, string filter, string Keyword, int page = 1)
{
#region ViewBag Resources
ViewBag.Title = Resources.Resource1.BookIndexTitle;
ViewBag.CreateLink = Resources.Resource1.CreateLink;
ViewBag.TitleDisplay = Resources.Resource1.TitleDisplay;
ViewBag.IsbnDisplay = Resources.Resource1.IsbnDisplay;
ViewBag.SummaryDisplay = Resources.Resource1.SummaryDisplay;
ViewBag.AuthorDisplay = Resources.Resource1.AuthorDisplay;
ViewBag.ThumbnailDisplay = Resources.Resource1.ThumbnailDisplay;
ViewBag.PriceDisplay = Resources.Resource1.PriceDisplay;
ViewBag.PublishedDisplay = Resources.Resource1.PublishedDisplay;
ViewBag.EditLink = Resources.Resource1.EditLink;
ViewBag.DetailsLink = Resources.Resource1.DetailsLink;
ViewBag.DeleteLink = Resources.Resource1.DeleteLink;
#endregion
#region ViewBag Sort Params
ViewBag.TitleSortParam = (sortOrder == "Title") ? "Title desc" : "Title";
ViewBag.IsbnSortParam = (sortOrder == "Isbn") ? "Isbn desc" : "Isbn";
ViewBag.AuthorSortParam = (sortOrder == "Author") ? "Author desc" : "Author";
ViewBag.PriceSortParam = (sortOrder == "Price") ? "Price desc" : "Price";
ViewBag.PublishedSortParam = (String.IsNullOrEmpty(sortOrder)) ? "Published desc" : "";
// Default the sort order
if (String.IsNullOrEmpty(sortOrder))
{
sortOrder = "Published desc";
}
ViewBag.CurrentSortOrder = sortOrder;
#endregion
var books = from b in db.Books select b;
#region Keyword Search
if (!String.IsNullOrEmpty(Keyword))
{
books = books.Where(b => b.Title.ToUpper().Contains(Keyword.ToUpper()) || b.Author.ToUpper().Contains(Keyword.ToUpper()));
// Should we redirect because of only one result?
if (books.Count() == 1)
{
Book book = books.First();
return RedirectToAction("Details", new { id = book.ID });
}
}
ViewBag.CurrentKeyword = String.IsNullOrEmpty(Keyword) ? "" : Keyword;
#endregion
#region Filter switch
switch (filter)
{
case "NewReleases":
var startDate = DateTime.Today.AddDays(-14);
books = books.Where(b => b.Published <= DateTime.Today.Date
&& b.Published >= startDate
);
break;
case "ComingSoon":
books = books.Where(b => b.Published > DateTime.Today.Date);
break;
default:
// No filter needed
break;
}
ViewBag.CurrentFilter = String.IsNullOrEmpty(filter) ? "" : filter;
#endregion
books = books.OrderBy(sortOrder);
int maxRecords = 1;
int currentPage = page - 1;
// Get all book titles
ViewBag.BookTitles = FormatBooksForAutocomplete();
return View(books.ToPagedList(currentPage, maxRecords));
}
private string FormatBooksForAutocomplete()
{
string bookTitles = String.Empty;
var books = from b in db.Books select b;
foreach (Book book in books)
{
if (bookTitles.Length > 0)
{
bookTitles += "|";
}
bookTitles += book.Title;
}
return bookTitles;
}
//
// GET: /Books/Details/5
public ActionResult Details(int id = 0, string bookTitle = "")
{
Book book = db.Books.Find(id);
return View(book);
}
//
// GET: /Books/Create
public ActionResult Create()
{
return View();
}
//
// POST: /Books/Create
[HttpPost]
public ActionResult Create(Book book, HttpPostedFileBase file)
{
if (ModelState.IsValid)
{
// Upload our file
book.Thumbnail = FileUpload.UploadFile(file);
db.Books.Add(book);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(book);
}
//
// GET: /Books/Edit/5
public ActionResult Edit(int id)
{
Book book = db.Books.Find(id);
return View(book);
}
//
// POST: /Books/Edit/5
[HttpPost]
public ActionResult Edit(Book book, HttpPostedFileBase file)
{
if (ModelState.IsValid)
{
// Delete old file
FileUpload.DeleteFile(book.Thumbnail);
// Upload our file
book.Thumbnail = FileUpload.UploadFile(file);
db.Entry(book).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
return View(book);
}
//
// GET: /Books/Delete/5
public ActionResult Delete(int id)
{
Book book = db.Books.Find(id);
return View(book);
}
//
// POST: /Books/Delete/5
[HttpPost, ActionName("Delete")]
public ActionResult DeleteConfirmed(int id)
{
Book book = db.Books.Find(id);
// Delete old file
FileUpload.DeleteFile(book.Thumbnail);
db.Books.Remove(book);
db.SaveChanges();
return RedirectToAction("Index");
}
protected override void Dispose(bool disposing)
{
db.Dispose();
base.Dispose(disposing);
}
}
}
最后book/index view需要更新去初始化jQuery的自動完成。要做的第一件事是使用@節標記，包括必要的JavaScript和CSS文件。接下來，以前創建的搜索文本框更新設置一個鍵的IDwordSearch。最后，JavaScript代碼添加在視圖的底部去在搜索文本框上建立自動完成功能。此JavaScript是有意添加在view的底部，以確保完全呈現給用戶，因為在用戶的電腦上建立數據是一項工作，Javascript處理可能會“堵塞”頁面加載。（譯者：先呈現數據再執行javascript，js不是像傳統那樣放在head標簽里），這取決于結果的數量。代碼如下：
展開查看代碼
@model PagedList.IPagedList<MvcApplication.Models.Book>
@if (IsAjax)
{
Layout = null;
}
@section JavascriptAndCSS {
<link rel="stylesheet" href="@Url.Content("~/Content/jquery.autocomplete.css")" type="text/css" />
<script type="text/javascript" src="@Url.Content("~/Scripts/jquery.autocomplete.js")"></script>
<script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.min.js")" type="text/javascript"></script>
}
<h2>@MvcApplication4.Resources.Resource1.BookIndexTitle</h2>
<p>
@Html.ActionLink("Create New", "Create")
</p>
<p>
Show:
@if (ViewBag.CurrentFilter != "")
{
@Ajax.ActionLink("All", "Index", new { sortOrder = ViewBag.CurrentSortOrder, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
}
else
{
@:All
}
|
@if (ViewBag.CurrentFilter != "NewReleases")
{
@Ajax.ActionLink("New Releases", "Index", new { filter = "NewReleases", sortOrder = ViewBag.CurrentSortOrder, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
}
else
{
@:New Releases
}
|
@if (ViewBag.CurrentFilter != "ComingSoon")
{
@Ajax.ActionLink("Coming Soon", "Index", new { filter = "ComingSoon", sortOrder = ViewBag.CurrentSortOrder, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
}
else
{
@:Coming Soon
}
</p>
@using (Html.BeginForm())
{
@:Search: @Html.TextBox("Keyword", (string)ViewBag.CurrentKeyword, new { id = "KeywordSearch" }) <input type="submit" value="Search" />
}
@Html.Partial("_Paging")
<table>
<tr>
<th>
@Ajax.ActionLink("Title", "Index", new { sortOrder = ViewBag.TitleSortParam, filter = ViewBag.CurrentFilter, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
</th>
<th>
@Ajax.ActionLink("Isbn", "Index", new { sortOrder = ViewBag.IsbnSortParam, filter = ViewBag.CurrentFilter, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
</th>
<th>
Summary
</th>
<th>
@Ajax.ActionLink("Author", "Index", new { sortOrder = ViewBag.AuthorSortParam, filter = ViewBag.CurrentFilter, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
</th>
<th>
Thumbnail
</th>
<th>
@Ajax.ActionLink("Price", "Index", new { sortOrder = ViewBag.PriceSortParam, filter = ViewBag.CurrentFilter, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
</th>
<th>
@Ajax.ActionLink("Published", "Index", new { sortOrder = ViewBag.PublishedSortParam, filter = ViewBag.CurrentFilter, Keyword = ViewBag.CurrentKeyword }, new AjaxOptions { UpdateTargetId = "main" })
</th>
<th></th>
</tr>
@foreach (var item in Model)
{
<tr>
<td>
@Html.DisplayFor(modelItem => item.Title)
</td>
<td>
@Html.DisplayFor(modelItem => item.Isbn)
</td>
<td>
@Html.DisplayFor(modelItem => item.Summary)
</td>
<td>
@Html.DisplayFor(modelItem => item.Author)
</td>
<td>
@Html.DisplayFor(modelItem => item.Thumbnail)
</td>
<td>
@Html.DisplayFor(modelItem => item.Price)
</td>
<td>
@Html.DisplayFor(modelItem => item.Published)
</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>
@Html.Partial("_Paging")
<script type="text/javascript">
$(document).ready(function () {
var data = "@ViewBag.BookTitles".split("|");
$("#KeywordSearch").autocomplete(data);
});
</script>
為了實施選項2，一個Ajax搜索，而不是傳遞數據數組到自動完成函數，您可以傳遞一個URL。URL將需要接受查詢字符串變量：q。這包含用戶輸入的搜索值。這將用于執行書本上包含部分匹配的搜索，并返回以分隔符分隔的字符串。JQuery文檔中含有較多的這樣的成品例子，也有其他的例子，去更新的輸出結果（可能包括書的封面的縮略圖）。
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