问题
How can dynamic breadcrumbs be achieved with ASP.net MVC?
If you are curious about what breadcrumbs are:
What are breadcrumbs? Well, if you have ever browsed an online store or read posts in a forum, you have likely encountered breadcrumbs. They provide an easy way to see where you are on a site. Sites like Craigslist use breadcrumbs to describe the user's location. Above the listings on each page is something that looks like this:
s.f. bayarea craigslist > city of san francisco > bicycles
EDIT
I realize what is possible with the SiteMapProvider. I am also aware of the providers out there on the net that will let you map sitenodes to controllers and actions.
But, what about when you want a breadcrumb's text to match some dynamic value, like this:
Home > Products > Cars > Toyota
Home > Products > Cars > Chevy
Home > Products > Execution Equipment > Electric Chair
Home > Products > Execution Equipment > Gallows
... where the product categories and the products are records from a database. Some links should be defined statically (Home for sure).
I am trying to figure out how to do this, but I'm sure someone has already done this with ASP.net MVC.
回答1:
There is a tool to do this on codeplex: http://mvcsitemap.codeplex.com/ [project moved to github]
Edit:
There is a way to derive a SiteMapProvider from a database: http://www.asp.net/Learn/data-access/tutorial-62-cs.aspx
You might be able to modify the mvcsitemap tool to use that to get what you want.
回答2:
Sitemap's are definitely one way to go... alternatively, you can write one yourself! (of course as long as standard MVC rules are followed)... I just wrote one, I figured I would share here.
@Html.ActionLink("Home", "Index", "Home")
@if(ViewContext.RouteData.Values["controller"].ToString() != "Home") {
@:> @Html.ActionLink(ViewContext.RouteData.Values["controller"].ToString(), "Index", ViewContext.RouteData.Values["controller"].ToString())
}
@if(ViewContext.RouteData.Values["action"].ToString() != "Index"){
@:> @Html.ActionLink(ViewContext.RouteData.Values["action"].ToString(), ViewContext.RouteData.Values["action"].ToString(), ViewContext.RouteData.Values["controller"].ToString())
}
Hopefully someone will find this helpful, this is exactly what I was looking for when I searched SO for MVC breadcrumbs.
回答3:
ASP.NET 5 (aka ASP.NET Core), MVC Core Solution
In ASP.NET Core, things are further optimized as we don't need to stringify the markup in the extension method.
In ~/Extesions/HtmlExtensions.cs:
using System.Text.RegularExpressions;
using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Mvc.Rendering;
namespace YourProjectNamespace.Extensions
{
public static class HtmlExtensions
{
private static readonly HtmlContentBuilder _emptyBuilder = new HtmlContentBuilder();
public static IHtmlContent BuildBreadcrumbNavigation(this IHtmlHelper helper)
{
if (helper.ViewContext.RouteData.Values["controller"].ToString() == "Home" ||
helper.ViewContext.RouteData.Values["controller"].ToString() == "Account")
{
return _emptyBuilder;
}
string controllerName = helper.ViewContext.RouteData.Values["controller"].ToString();
string actionName = helper.ViewContext.RouteData.Values["action"].ToString();
var breadcrumb = new HtmlContentBuilder()
.AppendHtml("<ol class='breadcrumb'><li>")
.AppendHtml(helper.ActionLink("Home", "Index", "Home"))
.AppendHtml("</li><li>")
.AppendHtml(helper.ActionLink(controllerName.Titleize(),
"Index", controllerName))
.AppendHtml("</li>");
if (helper.ViewContext.RouteData.Values["action"].ToString() != "Index")
{
breadcrumb.AppendHtml("<li>")
.AppendHtml(helper.ActionLink(actionName.Titleize(), actionName, controllerName))
.AppendHtml("</li>");
}
return breadcrumb.AppendHtml("</ol>");
}
}
}
~/Extensions/StringExtensions.cs remains the same as below (scroll down to see the MVC5 version).
In razor view, we don't need Html.Raw, as Razor takes care of escaping when dealing with IHtmlContent:
....
....
<div class="container body-content">
<!-- #region Breadcrumb -->
@Html.BuildBreadcrumbNavigation()
<!-- #endregion -->
@RenderBody()
<hr />
...
...
ASP.NET 4, MVC 5 Solution
=== ORIGINAL / OLD ANSWER BELOW ===
(Expanding on Sean Haddy's answer above)
If you want to make it extension-driven (keeping Views clean), you can do something like:
In ~/Extesions/HtmlExtensions.cs:
(compatible with MVC5 / bootstrap)
using System.Text;
using System.Web.Mvc;
using System.Web.Mvc.Html;
namespace YourProjectNamespace.Extensions
{
public static class HtmlExtensions
{
public static string BuildBreadcrumbNavigation(this HtmlHelper helper)
{
// optional condition: I didn't wanted it to show on home and account controller
if (helper.ViewContext.RouteData.Values["controller"].ToString() == "Home" ||
helper.ViewContext.RouteData.Values["controller"].ToString() == "Account")
{
return string.Empty;
}
StringBuilder breadcrumb = new StringBuilder("<ol class='breadcrumb'><li>").Append(helper.ActionLink("Home", "Index", "Home").ToHtmlString()).Append("</li>");
breadcrumb.Append("<li>");
breadcrumb.Append(helper.ActionLink(helper.ViewContext.RouteData.Values["controller"].ToString().Titleize(),
"Index",
helper.ViewContext.RouteData.Values["controller"].ToString()));
breadcrumb.Append("</li>");
if (helper.ViewContext.RouteData.Values["action"].ToString() != "Index")
{
breadcrumb.Append("<li>");
breadcrumb.Append(helper.ActionLink(helper.ViewContext.RouteData.Values["action"].ToString().Titleize(),
helper.ViewContext.RouteData.Values["action"].ToString(),
helper.ViewContext.RouteData.Values["controller"].ToString()));
breadcrumb.Append("</li>");
}
return breadcrumb.Append("</ol>").ToString();
}
}
}
In ~/Extensions/StringExtensions.cs:
using System.Globalization;
using System.Text.RegularExpressions;
namespace YourProjectNamespace.Extensions
{
public static class StringExtensions
{
public static string Titleize(this string text)
{
return CultureInfo.CurrentCulture.TextInfo.ToTitleCase(text).ToSentenceCase();
}
public static string ToSentenceCase(this string str)
{
return Regex.Replace(str, "[a-z][A-Z]", m => m.Value[0] + " " + char.ToLower(m.Value[1]));
}
}
}
Then use it like (in _Layout.cshtml for example):
....
....
<div class="container body-content">
<!-- #region Breadcrumb -->
@Html.Raw(Html.BuildBreadcrumbNavigation())
<!-- #endregion -->
@RenderBody()
<hr />
...
...
回答4:
I built this nuget package to solve this problem for myself:
https://www.nuget.org/packages/MvcBreadCrumbs/
You can contribute here if you have ideas for it:
https://github.com/thelarz/MvcBreadCrumbs
回答5:
Maarten Balliauw's MvcSiteMapProvider worked pretty well for me.
I created a small mvc app to test his provider: MvcSiteMapProvider Test (404)
回答6:
For whoever is interested, I did an improved version of a HtmlExtension that is also considering Areas and in addition uses Reflection to check if there is a Default controller inside an Area or a Index action inside a Controller:
public static class HtmlExtensions
{
public static MvcHtmlString BuildBreadcrumbNavigation(this HtmlHelper helper)
{
string area = (helper.ViewContext.RouteData.DataTokens["area"] ?? "").ToString();
string controller = helper.ViewContext.RouteData.Values["controller"].ToString();
string action = helper.ViewContext.RouteData.Values["action"].ToString();
// add link to homepage by default
StringBuilder breadcrumb = new StringBuilder(@"
<ol class='breadcrumb'>
<li>" + helper.ActionLink("Homepage", "Index", "Home", new { Area = "" }, new { @class="first" }) + @"</li>");
// add link to area if existing
if (area != "")
{
breadcrumb.Append("<li>");
if (ControllerExistsInArea("Default", area)) // by convention, default Area controller should be named Default
{
breadcrumb.Append(helper.ActionLink(area.AddSpaceOnCaseChange(), "Index", "Default", new { Area = area }, new { @class = "" }));
}
else
{
breadcrumb.Append(area.AddSpaceOnCaseChange());
}
breadcrumb.Append("</li>");
}
// add link to controller Index if different action
if ((controller != "Home" && controller != "Default") && action != "Index")
{
if (ActionExistsInController("Index", controller, area))
{
breadcrumb.Append("<li>");
breadcrumb.Append(helper.ActionLink(controller.AddSpaceOnCaseChange(), "Index", controller, new { Area = area }, new { @class = "" }));
breadcrumb.Append("</li>");
}
}
// add link to action
if ((controller != "Home" && controller != "Default") || action != "Index")
{
breadcrumb.Append("<li>");
//breadcrumb.Append(helper.ActionLink((action.ToLower() == "index") ? controller.AddSpaceOnCaseChange() : action.AddSpaceOnCaseChange(), action, controller, new { Area = area }, new { @class = "" }));
breadcrumb.Append((action.ToLower() == "index") ? controller.AddSpaceOnCaseChange() : action.AddSpaceOnCaseChange());
breadcrumb.Append("</li>");
}
return MvcHtmlString.Create(breadcrumb.Append("</ol>").ToString());
}
public static Type GetControllerType(string controller, string area)
{
string currentAssembly = Assembly.GetExecutingAssembly().GetName().Name;
IEnumerable<Type> controllerTypes = Assembly.GetExecutingAssembly().GetTypes().Where(o => typeof(IController).IsAssignableFrom(o));
string typeFullName = String.Format("{0}.Controllers.{1}Controller", currentAssembly, controller);
if (area != "")
{
typeFullName = String.Format("{0}.Areas.{1}.Controllers.{2}Controller", currentAssembly, area, controller);
}
return controllerTypes.Where(o => o.FullName == typeFullName).FirstOrDefault();
}
public static bool ActionExistsInController(string action, string controller, string area)
{
Type controllerType = GetControllerType(controller, area);
return (controllerType != null && new ReflectedControllerDescriptor(controllerType).GetCanonicalActions().Any(x => x.ActionName == action));
}
public static bool ControllerExistsInArea(string controller, string area)
{
Type controllerType = GetControllerType(controller, area);
return (controllerType != null);
}
public static string AddSpaceOnCaseChange(this string text)
{
if (string.IsNullOrWhiteSpace(text))
return "";
StringBuilder newText = new StringBuilder(text.Length * 2);
newText.Append(text[0]);
for (int i = 1; i < text.Length; i++)
{
if (char.IsUpper(text[i]) && text[i - 1] != ' ')
newText.Append(' ');
newText.Append(text[i]);
}
return newText.ToString();
}
}
If can definitely can be improved (probably does not cover all the possible cases), but it did not failed me until now.
回答7:
For those using ASP.NET Core 2.0 and looking for a more decoupled approach than vulcan's HtmlHelper, I recommend having a look at using a partial view with dependency injection.
Below is a simple implementation which can easily be molded to suit your needs.
The breadcrumb service (./Services/BreadcrumbService.cs):
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System;
using System.Collections.Generic;
namespace YourNamespace.YourProject
{
public class BreadcrumbService : IViewContextAware
{
IList<Breadcrumb> breadcrumbs;
public void Contextualize(ViewContext viewContext)
{
breadcrumbs = new List<Breadcrumb>();
string area = $"{viewContext.RouteData.Values["area"]}";
string controller = $"{viewContext.RouteData.Values["controller"]}";
string action = $"{viewContext.RouteData.Values["action"]}";
object id = viewContext.RouteData.Values["id"];
string title = $"{viewContext.ViewData["Title"]}";
breadcrumbs.Add(new Breadcrumb(area, controller, action, title, id));
if(!string.Equals(action, "index", StringComparison.OrdinalIgnoreCase))
{
breadcrumbs.Insert(0, new Breadcrumb(area, controller, "index", title));
}
}
public IList<Breadcrumb> GetBreadcrumbs()
{
return breadcrumbs;
}
}
public class Breadcrumb
{
public Breadcrumb(string area, string controller, string action, string title, object id) : this(area, controller, action, title)
{
Id = id;
}
public Breadcrumb(string area, string controller, string action, string title)
{
Area = area;
Controller = controller;
Action = action;
if (string.IsNullOrWhiteSpace(title))
{
Title = Regex.Replace(CultureInfo.CurrentCulture.TextInfo.ToTitleCase(string.Equals(action, "Index", StringComparison.OrdinalIgnoreCase) ? controller : action), "[a-z][A-Z]", m => m.Value[0] + " " + char.ToLower(m.Value[1]));
}
else
{
Title = title;
}
}
public string Area { get; set; }
public string Controller { get; set; }
public string Action { get; set; }
public object Id { get; set; }
public string Title { get; set; }
}
}
Register the service in startup.cs after AddMvc():
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.AddTransient<BreadcrumbService>();
Create a partial to render the breadcrumbs (~/Views/Shared/Breadcrumbs.cshtml):
@using YourNamespace.YourProject.Services
@inject BreadcrumbService BreadcrumbService
@foreach(var breadcrumb in BreadcrumbService.GetBreadcrumbs())
{
<a asp-area="@breadcrumb.Area" asp-controller="@breadcrumb.Controller" asp-action="@breadcrumb.Action" asp-route-id="@breadcrumb.Id">@breadcrumb.Title</a>
}
At this point, to render the breadcrumbs simply call Html.Partial("Breadcrumbs") or Html.PartialAsync("Breadcrumbs").
来源：https://stackoverflow.com/questions/1066777/how-can-dynamic-breadcrumbs-be-achieved-with-asp-net-mvc