[转载]ASP.NET MVC3 20个秘方-(18)Auto Complete(自动完成)

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[转载]【译】MVC3 20个秘方-(18)Auto Complete(自动完成) – 技术弟弟 – 博客园.

问题

当你查找一些特殊的东西,当你输入准确的词时,找到它可能是困难的(或者很耗时)。在输入的时候展示出结果(自动完成),使查找变得更简单。

解决方案

使用JQuery自动完成插件,更新现有图书列表页面上的搜索,当用户键入的时候立即显示结果。

讨论

自动完成插件是不会象JQuery基本库一样自动包含在MVC项目中的,所以需要做的第一件事就是的是下载插件
访问http://jQuery.com/。两个主要的文件是必需的:JavaScript文件和CSS文件。把新下载的JavaScript文件放到你MVC应用程序的script 文件夹下。CSS文件可以直接添加到您的content目录。

这个配方也将介绍在view中使用 rendering sections。在shared文件夹下layout中自动添加了2个JavaScript文件和1个css文件。这些是Ajax和不唐突的Ajax和 网站主css文件。每次加载的内容越多,页面视图加载越慢。与其在每个页面都去包含可能不必要的javascript和css 文件,不如在layout中添加一个新的RenderSection()。这允许特别的view在<head>标签去加载特别的 javascript或css,但不是每页都添加他们。

下边是一个更新后的Views/Shared/_Layout.cshtml,他使用了一个新的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("Français", "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文件被留下来了,因为css在每个也都需要,并且绝大多数网页也需要JQuery。然而新的JQuery文件和不唐突的AJAX不是每个页面都需要的。

现在,有两种方式使用Autocomplete 插件:

  1. 在javascript中设置要搜索的数据。
  2. 当用户输入时通过ajax检索。

在我使用这个插件的经验看来,我发现使用解决方案1时自动完成更快。因为它并不需要每次从数据库中请求数据。然而,使用这种解决方案的限制:只有这么多字符,可传递到function中,大量的JavaScript可能会导致
用户的计算机上页面加载缓慢。经过一些试验和错误,我已经确定神奇的数字是大约40,000个结果。如果结果数量超过此,最好使用选项2;否则,始终坚持,因为搜索选项1是瞬时,而不是有轻微的延迟。

在这个例子中,将搜索书籍,我们没有超过40000,所以将使用选项1。BooksController现在必须更新, 以设置ViewBag为book title。自动完成功能需要支持一个JavaScript数组的支持,所以书将管道(|)分开。然后在view中,书将被转换到一个数组,使用 JavaScript的split()函数。当用户完成键入他们的结果,他们应该有选择完全匹配标题,因此
这个函数将被更新。如果只有1本书返回并且用户执行了搜索,它会自动重定向到本书详细介绍页面。

我们要在bookcontroller 中更新Index Action 并添加一个私有方法名为:FormatBooksForAutocomplete。

代码如下:

展开查看代码

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的自动完成。要做的第一件事是使用@节标记,包括必要的JavaScript和CSS文件。接下来,以前创建的搜索 文本框更新设置一个键的IDwordSearch。最后,JavaScript代码添加在视图的底部去在搜索文本框上建立自动完成功能。此 JavaScript是有意添加在view的底部,以确保完全呈现给用户,因为在用户的电脑上建立数据是一项工作,Javascript处理可能会“堵 塞”页面加载。(译者:先呈现数据再执行javascript,js不是像传统那样放在head标签里),这取决于结果的数量。代码如下:

展开查看代码

@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
    }
    &nbsp; | &nbsp;
    @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
    }
    &nbsp; | &nbsp;
    @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>

为了实施选项2,一个Ajax搜索,而不是传递数据数组到自动完成函数,您可以传递一个URL。URL将需要接受查询字 符串变量:q。这包含用户输入的搜索值。这将用于执行书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文档中含有较多的这样的成品例 子,也有其他的例子,去更新的输出结果(可能包括书的封面的缩略图)。

另请参阅

Jquery.Autocomplete, RenderSection

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