在需要处理很多分类以及导航的时候，树形导航菜单就比较适合。例如在汽车之家上：

页面主要分两部分，左边是导航菜单，右边显示对应的内容。现在，我们就在ASP.NET MVC 4 下临摹一个，如下：

实现的效果包括：

1、点击导航菜单上的品牌，左侧显示该品牌下的所有车型。

2、点击导航菜单上的车系，左侧显示该车系下的所有车型。

3、点击左侧上方的字母导航，锚点跳到导航菜单的对应部分。

4、页面加载完毕，显示所有品牌和车系，即树形导航完全展开。

5、点击导航菜单上的品牌，收缩或展开对应的车系，收缩时，品牌前面图标为+号，展开时，品牌前面的图片为-号。

源码部分，在这里。

思路呢？

页面分成左右2部分，使用Bootstrap轻松实现：

复制
<div class="row">
    <div class="col-md-2 col-lg-2 col-sm-2">
    </div>
    <div class="col-md-10 col-lg-10 col-sm-10">
    </div>
</div>

左侧最上方的字母导航，被放在一个div中，页面加载的时候向控制器动态请求。

品牌上方的字母归类，比如奥迪上方的字母A，实际上是一个div。

品牌和车系放在了ul中，比如奥迪品牌以及奥迪下的奥迪A4和奥迪A6车系。车系被放在了dl中。

树形菜单采用模版比较合适，先把数据填充到模版，再把模版追加到页面元素。

当点击左侧树形导航上的品牌或车系，右侧通过iframe来呈现对应的内容。

领域先行。有关品牌和车系就抽象成如下的类：

复制
public class CarCategory
{
    public int Id { get; set; }
    public int ParentId { get; set; }
    public string Name { get; set; }
    public string FirstLetter { get; set; }
    public string AnchorName { get; set; }
    public int Level { get; set; }
    public short DelFlag { get; set; }
}

有关车型就抽象成如下的类：

复制
public class Car
{
    public int Id { get; set; }
    public int PinPaiId { get; set; }
    public int CheXiId { get; set; } 
    public string Name { get; set; }
}

页面左侧呈现树形导航需要向控制器请求json数据，大致格式是：

首字母

锚点名称

所有品牌

   品牌编号

   品牌名称

   所有车系

       车系编号

       车系名称

       车系下车型的总数量

貌似有3层，那就从最里面这层开始建模。有关车系在树形导航中的显示：

复制
public class CheXiForDisplay
{
    public int CheXiId { get; set; }
    public int TotalCount { get; set; }
    public string CheXiName { get; set; }
}

有关品牌在树形导航中的显示：

复制
public class PinPaiForDisplay
{
    public int PinPaiId { get; set; }
    public string PinPaiName { get; set; }
    public List<CheXiForDisplay> CheXis { get; set; }
}

有关品牌车系分组的：

复制
public class PinPaiCheXiForDisplay
{
    public string FirstLetter { get; set; }
    public string Anchor { get; set; }
    public List<PinPaiForDisplay> PinPais { get; set; }
}

数据源从哪里来？模拟了一个：

复制
public class Database
{
    public static IEnumerable<CarCategory> GetAllCarCategories()
    {
        return new List<CarCategory>
        {
            new CarCategory(){Id = 1, ParentId = 0, Name = "奥迪",FirstLetter = "A", AnchorName = "AA", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 2, ParentId = 0, Name = "宝马",FirstLetter = "B", AnchorName = "BB", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 3, ParentId = 0, Name = "保时捷",FirstLetter = "B", AnchorName = "BB", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 4, ParentId = 0, Name = "长安",FirstLetter = "C", AnchorName = "CC", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 5, ParentId = 0, Name = "大众",FirstLetter = "D", AnchorName = "DD", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 6, ParentId = 0, Name = "东风",FirstLetter = "D", AnchorName = "DD", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 7, ParentId = 0, Name = "丰田",FirstLetter = "F", AnchorName = "FF", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 8, ParentId = 0, Name = "福特",FirstLetter = "F", AnchorName = "FF", Level = 1, DelFlag = 0},
            new CarCategory(){Id = 9, ParentId = 1, Name = "奥迪A4",FirstLetter = "A", AnchorName = "AA", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 10, ParentId = 1, Name = "奥迪A6",FirstLetter = "A", AnchorName = "AA", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 11, ParentId = 2, Name = "宝马1",FirstLetter = "B", AnchorName = "BB", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 12, ParentId = 2, Name = "宝马2",FirstLetter = "B", AnchorName = "BB", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 13, ParentId = 3, Name = "保时捷1",FirstLetter = "B", AnchorName = "BB", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 14, ParentId = 3, Name = "保时捷2",FirstLetter = "B", AnchorName = "BB", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 15, ParentId = 4, Name = "长安1",FirstLetter = "C", AnchorName = "CC", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 16, ParentId = 4, Name = "长安2",FirstLetter = "C", AnchorName = "CC", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 17, ParentId = 5, Name = "大众1",FirstLetter = "D", AnchorName = "DD", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 18, ParentId = 5, Name = "大众2",FirstLetter = "D", AnchorName = "DD", Level = 2, DelFlag = 1},
            new CarCategory(){Id = 19, ParentId = 6, Name = "东风1",FirstLetter = "D", AnchorName = "DD", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 20, ParentId = 6, Name = "东风2",FirstLetter = "D", AnchorName = "DD", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 21, ParentId = 7, Name = "丰田1",FirstLetter = "F", AnchorName = "FF", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 22, ParentId = 7, Name = "丰田2",FirstLetter = "F", AnchorName = "FF", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 23, ParentId = 8, Name = "福特1",FirstLetter = "F", AnchorName = "AFF", Level = 2, DelFlag = 0},
            new CarCategory(){Id = 24, ParentId = 8, Name = "福特2",FirstLetter = "F", AnchorName = "AFF", Level = 2, DelFlag = 0}
        };
    }
    public static IEnumerable<Car> GetAllCars()
    {
        return new List<Car>
        {
            new Car(){Id = 1, PinPaiId = 1, CheXiId = 9, Name = "奥迪A401"},
            new Car(){Id = 2, PinPaiId = 1, CheXiId = 9, Name = "奥迪A402"},
            new Car(){Id = 3, PinPaiId = 1, CheXiId = 10, Name = "奥迪A601"},
            new Car(){Id = 4, PinPaiId = 1, CheXiId = 10, Name = "奥迪A602"},
            new Car(){Id = 5, PinPaiId = 2, CheXiId = 11, Name = "宝马101"},
            new Car(){Id = 6, PinPaiId = 2, CheXiId = 11, Name = "宝马102"},
            new Car(){Id = 7, PinPaiId = 2, CheXiId = 12, Name = "宝马201"},
            new Car(){Id = 8, PinPaiId = 2, CheXiId = 12, Name = "宝马202"},
            new Car(){Id = 9, PinPaiId = 3, CheXiId = 13, Name = "保时捷101"},
            new Car(){Id = 10, PinPaiId = 3, CheXiId = 13, Name = "保时捷102"},
            new Car(){Id = 11, PinPaiId = 3, CheXiId = 14, Name = "保时捷201"},
            new Car(){Id = 12, PinPaiId = 3, CheXiId = 14, Name = "保时捷202"},
            new Car(){Id = 13, PinPaiId = 4, CheXiId = 15, Name = "长安101"},
            new Car(){Id = 14, PinPaiId = 4, CheXiId = 15, Name = "长安102"},
            new Car(){Id = 15, PinPaiId = 4, CheXiId = 16, Name = "长安201"},
            new Car(){Id = 16, PinPaiId = 4, CheXiId = 16, Name = "长安202"},
            new Car(){Id = 17, PinPaiId = 5, CheXiId = 17, Name = "大众101"},
            new Car(){Id = 18, PinPaiId = 5, CheXiId = 17, Name = "大众102"},
            new Car(){Id = 19, PinPaiId = 5, CheXiId = 18, Name = "大众201"},
            new Car(){Id = 20, PinPaiId = 5, CheXiId = 18, Name = "大众202"},
            new Car(){Id = 21, PinPaiId = 6, CheXiId = 19, Name = "东风101"},
            new Car(){Id = 22, PinPaiId = 6, CheXiId = 19, Name = "东风102"},
            new Car(){Id = 23, PinPaiId = 6, CheXiId = 20, Name = "东风201"},
            new Car(){Id = 24, PinPaiId = 6, CheXiId = 20, Name = "东风202"},
            new Car(){Id = 25, PinPaiId = 7, CheXiId = 21, Name = "丰田101"},
            new Car(){Id = 26, PinPaiId = 7, CheXiId = 21, Name = "丰田102"},
            new Car(){Id = 27, PinPaiId = 7, CheXiId = 22, Name = "丰田201"},
            new Car(){Id = 28, PinPaiId = 7, CheXiId = 22, Name = "丰田202"},
            new Car(){Id = 29, PinPaiId = 8, CheXiId = 23, Name = "福特101"},
            new Car(){Id = 30, PinPaiId = 8, CheXiId = 23, Name = "福特102"},
            new Car(){Id = 31, PinPaiId = 8, CheXiId = 24, Name = "福特201"},
            new Car(){Id = 32, PinPaiId = 8, CheXiId = 24, Name = "福特202"}
        };
    }
}

好，现在可以向控制器要数据了。

复制
 public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }
    //获取所有首字母以及锚点的json
    public ActionResult GetFirstLettersJson()
    {
        var allCarCategories = Database.GetAllCarCategories();
        var result = from l in allCarCategories
            group l by l.FirstLetter
            into g
            select new {firstletter = g.Key, anchor=g.ToList()[0].AnchorName};
        return Json(result, JsonRequestBehavior.AllowGet);
    }
    //获取按首字母分组后的品牌车系json
    public ActionResult GetPinPaiCheXiJson() 
    {
        var allPinPais = Database.GetAllCarCategories().Where(c => c.Level == 1).OrderBy(c => c.FirstLetter);
        var allPinPaisGroup = from p in allPinPais
            group p by new
            {
                p.FirstLetter,
                p.AnchorName
            };
        List<PinPaiCheXiForDisplay> result1 = new List<PinPaiCheXiForDisplay>();
        foreach (var item in allPinPaisGroup)
        {
            //品牌车系
            PinPaiCheXiForDisplay pinPaiCheXiForDisplay = new PinPaiCheXiForDisplay();
            pinPaiCheXiForDisplay.FirstLetter = item.Key.FirstLetter;
            pinPaiCheXiForDisplay.Anchor = item.Key.AnchorName;
            
            //品牌
            List<PinPaiForDisplay> pinPaiForDisplays = new List<PinPaiForDisplay>();
            foreach (var pinpai in item.ToList())
            {
                PinPaiForDisplay pinPaiForDisplay = new PinPaiForDisplay();
                pinPaiForDisplay.PinPaiId = pinpai.Id;
                pinPaiForDisplay.PinPaiName = pinpai.Name;
                
                //车系
                List<CheXiForDisplay> cheXiForDisplays = new List<CheXiForDisplay>();
                var cheXis = Database.GetAllCarCategories().Where(c => c.ParentId == pinpai.Id).OrderBy(c => c.Id);
                foreach (var chexi in cheXis)
                {
                    CheXiForDisplay cheXiForDisplay = new CheXiForDisplay();
                    cheXiForDisplay.CheXiId = chexi.Id;
                    cheXiForDisplay.CheXiName = chexi.Name;
                    cheXiForDisplay.TotalCount = cheXis.Count();
                    cheXiForDisplays.Add(cheXiForDisplay);
                }
                pinPaiForDisplay.CheXis = cheXiForDisplays;
                pinPaiForDisplays.Add(pinPaiForDisplay);
            }
            pinPaiCheXiForDisplay.PinPais = pinPaiForDisplays;
            result1.Add(pinPaiCheXiForDisplay);
        }
        return Json(result1, JsonRequestBehavior.AllowGet);
    }
    //根据品牌Id显示车型
    public ActionResult GetCheXingsByPId(int pid)
    {
        var cars = Database.GetAllCars().Where(c => c.PinPaiId == pid);
        return View(cars);
    }
    //根据车系Id显示车型
    public ActionResult GetCheXingsByChexiId(int cxid)
    {
        var cars = Database.GetAllCars().Where(c => c.CheXiId == cxid);
        return View(cars);
    }
}

在Shared/_Layout.cshtml中，该引用的css,js都要引用上。

复制
<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width" />
    <title>@ViewBag.Title</title>
    <link href="~/bootstrap/css/bootstrap.min.css" rel="external nofollow"  rel="stylesheet" />
    @Styles.Render("~/Content/css")
    @RenderSection("styles", required: false)
    @Scripts.Render("~/bundles/jquery")
    <script src="~/bootstrap/js/bootstrap.min.js"></script>
</head>
<body>
    @RenderBody()
    
    @RenderSection("scripts", required: false)
</body>

Home/Index.cshtml就负责显示就行了。

复制
@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}
@section styles
{
    <link href="~/Content/sidemenu.css" rel="external nofollow"  rel="stylesheet" />
}
<div class="row">
    <div class="col-md-2 col-lg-2 col-sm-2">
        <!--字母导航开始-->
        <div id="lDaoHang">
        </div>
        <!--字母导航结束-->
        <!--树开始-->
        <div id="cTreeDiv" style="overflow-x: hidden; overflow-y: scroll; height: 550px; width: 99%;">
        </div>
        <!--树结束-->
        <div>
            <dl id="test"></dl>
        </div>
    </div>
    <div class="col-md-10 col-lg-10 col-sm-10">
        <div class="carContent" id="carContent">
            <iframe id="frameCar" src="" scrolling="no" frameborder="0" height="100%" width="100%" onload="this.height=this.contentWindow.document.documentElement.scrollHeight"></iframe>
        </div>
    </div>
</div>
@section scripts
{
    <script src="~/Scripts/jquery.tmpl.min.js"></script>
    <script type="text/javascript">
        $(function () {
            //加载首字母
            $.getJSON('@Url.Action("GetFirstLettersJson", "Home")', function (data) {
                $('#firstLetterTemplate').tmpl(data).appendTo('#lDaoHang');
            });
            //加载所有品牌车系
            $.getJSON('@Url.Action("GetPinPaiCheXiJson", "Home")', function (data) {
                $('#pinpaiTemplate').tmpl(data).appendTo('#cTreeDiv');
                $('.pLink').each(function () {
                    pinPaiInitialState($(this));
                });
            });
            //隐藏ifame所在div
            $("#carContent").css("display", "none");
            //点击品牌
            $('#cTreeDiv').on("click", ".pLink", function () {
                //切换
                togglePinPaiState($(this));
                //显示右边区域
                var url = "/Home/GetCheXingsByPId?pid=" + $(this).attr('id');
                $("#frameCar").attr("src", url);
                $("#carContent").css("display", "block");
            });
            //点击车系
            $('#cTreeDiv').on("click", ".cxLink", function () {
                //显示右边区域
                var url = "/Home/GetCheXingsByChexiId?cxid=" + $(this).attr('id');
                $("#frameCar").attr("src", url);
                $("#carContent").css("display", "block");
            });
        });
        //品牌的初始状态,即把车系隐藏和品牌前面的图标为+号
        var pstate = 0;
        //品牌只有2种状态：所有车系隐藏，品牌前面的图标变为为+号；要么显示品牌下的所有车系，品牌前面的图标变为-号
        //把车系隐藏和品牌前面的图标为+号，记为状态0
        //把车系隐藏和品牌前面的图标为-号，记为状态1
        function togglePinPaiState($pinpai) {
            if (pstate == 0) {
                var $i = $pinpai.parent().find("i");
                var attr = $i.attr('class');
                if (typeof attr !== typeof undefined && attr !== false) {
                    $i.removeClass("iconHide");
                }
                $i.addClass("iconShow");
                $pinpai.parent().parent().find("dl").show();
                pstate = 1;
            } else {
                var $j = $pinpai.parent().find("i");
                var attr1 = $j.attr('class');
                if (typeof attr1 !== typeof undefined && attr1 !== false) {
                    $j.removeClass("iconShow");
                }
                $j.addClass("iconHide");
                $pinpai.parent().parent().find("dl").hide();
                pstate = 0;
            }
        }
        function pinPaiInitialState($pinpai) {
            pstate = 0;
            togglePinPaiState($pinpai);
        }
    </script>
    <!--首字母模版-->
    <script id="firstLetterTemplate" type="text/x-jQuery-tmpl">
        <div class="lWrapper">
            <a href="#${anchor}" rel="external nofollow"  class="lLink">${firstletter}</a>
        </div>
    </script>
    <!--品牌模版-->
    <script id="pinpaiTemplate" type="text/x-jQuery-tmpl">
        <div class="lHeader" id="${Anchor}">${FirstLetter}</div>
        <ul class="uTree">
            {{if PinPais}}
            {{each PinPais}}
            <li>
                <h5 class="font-bold">
                    <a href="javascript:void(0)" rel="external nofollow"  rel="external nofollow"  class="pLink" id="${$value.PinPaiId}"><i></i>${$value.PinPaiName}</a>
                </h5>
                <dl>
                    {{tmpl(CheXis) "#chexiTemplate"}}
                </dl>
            </li>
            {{/each}}
            {{else}}
            <li>没有对应品牌</li>
            {{/if}}
                
        </ul>
    </script>
    <!--车系模版-->
    <script id="chexiTemplate" type="text/x-jQuery-tmpl">
        <dd><a id="${CheXiId}" href="javascript:void(0)" rel="external nofollow"  rel="external nofollow"  class="cxLink">${CheXiName}<em>(${TotalCount})</em></a></dd>
    </script>
}

以上，

• 从控制器返回的有关树形菜单的json数据，先填充到jquery.tmpl.min.js模版中，然后追加到页面上。
• 树形菜单的展开或收缩，通过全局变量pstate在0和1之间的切换来实现，页面初次加载给变量pstate一个初始值。

另外，点击树形导航上的品牌，iframe加载的视图是Home/GetCheXingsByPId.cshtml

复制
@model IEnumerable<MvcApplication1.Models.Car>
@{
    ViewBag.Title = "GetCheXingsByPId";
    Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>GetCheXingsByPId</h2>
<div>
    @foreach (var item in Model)
    {
        <p>@item.Name </p>
    
    }
</div>

点击树形导航上的车系，iframe加载的视图是Home/GetCheXingsByChexiId.cshtml

复制
@model IEnumerable<MvcApplication1.Models.Car>
@{
    ViewBag.Title = "GetCheXingsByChexiId";
    Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>GetCheXingsByChexiId</h2>
<div>
    @foreach (var item in Model)
    {
        <p>@item.Name </p>
    
    }
</div>

就这样。