[翻译]ASP.NET MVC 3 开发的20个秘诀（十）[20 Recipes for Programming MVC 3]：通过关键字进行列表搜索

议题

当排序、分页和筛选不能够帮助用户找到所需的内容，下一步最好的方法就是让用户输入他所想要查找的内容。

解决方案

使用Html.Helper创建表单和文本输入框，在筛选器选择结果的基础上用Linq Libary使用用户输入的关键字进行查询。

讨论

就像之前的秘诀所做的，添加关键字搜索需要修改Books和Index视图以及BooksController控制器。在视图中创建一个新的表单，添加新的输入关键字的文本框。此外，为了在用户搜索关键字时，保持用户选择的排序、筛选器选项就需要重新编辑原有代码。下面是修改后的Book和Index视图：

@model PagedList.IPagedList<MvcApplication4.Models.Book>           
<h2>@MvcApplication4.Resources.Resource1.BookIndexTitle</h2>
<p>
    @Html.ActionLink("Create New", "Create")
</p>
<p>
    Show:
    @if (ViewBag.CurrentFilter != "")
    {
        @Html.ActionLink("All", "Index", new {
        sortOrder = ViewBag.CurrentSortOrder,
        Keyword = ViewBag.CurrentKeyword })
    }
    else
    {
        @:All
    }
    &nbsp; | &nbsp;
    @if (ViewBag.CurrentFilter != "NewReleases")
    {
        @Html.ActionLink("New Releases", "Index", new {
        filter = "NewReleases",
        sortOrder = ViewBag.CurrentSortOrder,
        Keyword = ViewBag.CurrentKeyword })
    }
    else
    {
        @:New Releases
    }
    &nbsp; | &nbsp;
    @if (ViewBag.CurrentFilter != "ComingSoon")
    {
        @Html.ActionLink("Coming Soon", "Index", new {
        filter = "ComingSoon",
        sortOrder = ViewBag.CurrentSortOrder,
        Keyword = ViewBag.CurrentKeyword })
    }
    else
    {
        @:Coming Soon
    }
</p>

@using (Html.BeginForm())
{
    @:Search: @Html.TextBox("Keyword")
    <input type="submit" value="Search" />
}
    
@Html.Partial("_Paging")

<table>
    <tr>
        <th>
            @Html.ActionLink("Title", "Index", new {
                sortOrder = ViewBag.TitleSortParam,
                    filter = ViewBag.CurrentFilter,
                    Keyword = ViewBag.CurrentKeyword })
        </th>
        <th>
            @Html.ActionLink("Isbn", "Index", new {
                sortOrder = ViewBag.IsbnSortParam,
                    filter = ViewBag.CurrentFilter,
                    Keyword = ViewBag.CurrentKeyword })
        </th>
        <th>
            Summary
        </th>
        <th>
            @Html.ActionLink("Author", "Index", new {
                sortOrder = ViewBag.AuthorSortParam,
                    filter = ViewBag.CurrentFilter,
                        Keyword = ViewBag.CurrentKeyword })
        </th>
        <th>
            Thumbnail
        </th>
        <th>
            @Html.ActionLink("Price", "Index", new {
                sortOrder = ViewBag.PriceSortParam,
                    filter = ViewBag.CurrentFilter,
                        Keyword = ViewBag.CurrentKeyword })
        </th>
        <th>
            @Html.ActionLink("Published", "Index", new {
                sortOrder = ViewBag.PublishedSortParam,
                    filter = ViewBag.CurrentFilter,
                        Keyword = ViewBag.CurrentKeyword })
        </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")

需要修改分页视图，以维持目前搜索的关键字：

<p>
    @if (Model.HasPreviousPage)
    {
        @Html.ActionLink("<< First", "Index", new {
            page = 1,
            sortOrder = ViewBag.CurrentSortOrder,
            filter = ViewBag.CurrentFilter,
            Keyword = ViewBag.CurrentKeyword })
        @Html.Raw("&nbsp;");
        @Html.ActionLink("< Prev", "Index", new {
            page = Model.PageNumber - 1,
            sortOrder = ViewBag.CurrentSortOrder,
            filter = ViewBag.CurrentFilter,
            Keyword = ViewBag.CurrentKeyword })
    }
    else
    {
        @:<< First
        @Html.Raw("&nbsp;");
        @:< Prev
    }
    &nbsp;&nbsp;
    @if (Model.HasNextPage)
    {
        @Html.ActionLink("Next >", "Index", new {
            page = Model.PageNumber + 1,
                sortOrder = ViewBag.CurrentSortOrder,
                    filter = ViewBag.CurrentFilter,
                        Keyword = ViewBag.CurrentKeyword })
        @Html.Raw("&nbsp;");
        @Html.ActionLink("Last >>", "Index", new {
            page = Model.PageCount,
                sortOrder = ViewBag.CurrentSortOrder,
                    filter = ViewBag.CurrentFilter,
                        Keyword = ViewBag.CurrentKeyword })
    }
    else
    {
        @:Next >
        @Html.Raw("&nbsp;")
        @:Last >>
    }
</p>

最后，需要修改BooksController控制器。在下面这个例子中，修改Index()方法，添加一个新的输入参数，可以接受用户输入关键字搜索书籍标题和作者。如果需要添加其他字段的搜索，只需要修改下面的例子，包含额外的字段：

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 MvcApplication4.Models;
using MvcApplication4.Utils;
using PagedList;

namespace MvcApplication4.Controllers
{
    public class BooksController : Controller
    {
        private BookDBContext db = new BookDBContext();
        //
        // GET: /Books/
        public ViewResult Index(string sortOrder, string filter,
        string Keyword, int page = 1)
        {
            #region ViewBag Resources
            ...
            #endregion
            #region ViewBag Sort Params
            ...
            #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()));
            }
            ViewBag.CurrentKeyword =
            String.IsNullOrEmpty(Keyword) ? "" : Keyword;
            #endregion
            #region Filter Switch
            ...
            #endregion
            int maxRecords = 1;
            int currentPage = page - 1;
            return View(books.ToPagedList(currentPage,
            maxRecords));
        }
        ...
    }

}

参考

原书地址 书籍源代码