TAG | MVC
I came across this issue just at quitting time yesterday and was blown away when I realized what was happening.
The UsersController Index View (pre submit)
The UsersController Code
public class UsersController : Controller
{
List<string> users = new List<string> ()
{
"mace.windu",
"yoda",
"senator.amidala",
"anakin.skywalker",
"obiwan.kenobi"
};
public ActionResult Index()
{
return View( users );
}
[HttpPost]
public ActionResult Delete ( string[] userstodelete )
{
if ( userstodelete == null || userstodelete.Length == 0 )
{
throw new ArgumentException (
"argument must contain at least one entry",
"userstodelete" );
}
// code could go here to
// call out to some service to
// delete these users
TempData["deletedUsers"] = userstodelete;
foreach ( var user in userstodelete )
users.Remove ( user );
return View ("Index", users);
}
}
Problem
Looks like it should all work perfectly right? That’s what I thought. However, clicking “Delete Users” will only “delete” our pre-darth user “anakin.skywalker”.
Why?
Hint: Everything here is working exactly as it should.
code · debugging · html · MVC · Programming
The Asp.net Mvc 2.0 RTM came out last month and a lot of people are converting their projects over. If you’re just starting to manually move your projects over then stop what you are doing, download and run the Mvc Converter. It will save you eons of time and frustration.
If you are like me, however, and started porting your project over manually and are now knee deep in WTFBBQ sauce then follow the steps below and your project should be up and running in no time.
1. Back up your project. Just in case.
2. Open your project file(s) inside your favorite text editor (one with a decent find/replace system). Open the Find & Replace dialog and find "603c0e0b-db56-11dc-be95-000d561079b0", replacing it with "F85E285D-A4E0-4152-9332-AB1D724D3325". My project turned up 1 result.
3. Open the Web.Config files in the root of the project and the root of the /Views folder. Open the Find & Replace dialog again, this time searching for "System.Web.Mvc, Version=1.0.0.0" and replacing it with "System.Web.Mvc, Version=2.0.0.0".
4. Add the following BindingRedirect to the bottom of the root Web.Config, just before the </Configuration> node.
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35"/>
<bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0"/>
</dependentAssembly>
</assemblyBinding>
</runtime>
5. Open the solution in Visual Studio and replace the references to System.Web.Mvc 1.0 with the 2.0 assembly.
6. Finally, and only if you really need them, open a new MVC 2.0 project and copy all the files in the /Scripts folder to your project.
Enjoy your freshly migrated project!
Download the source code mentioned in this blog post.
A few weeks ago on the StackOverflow podcast, something Jeff said got me thinking. Jeff was discussing how the stackoverflow team implemented their route mappings:
Those routes are… the way we implemented them are actually like decorators. Attributes on the methods. - Jeff Atwood (stackoverflow episode #54)
This instantly piqued my interest and I completely zoned out for the rest of the podcast: caught up in working out the details of how I could do this for my own Asp.net MVC projects.
Coming up with the actual attribute code was easy; writing the code to set up all the Routes using only data defined in by the attribute was tricky.
Being new to attributes, and reflection in general, it took me a few hours until I had a very basic demo working. However, I was really starting to like where it was going.
As a side note: There are lot of “helper” classes and objects in the route attribute project (it feels cluttered to me) and the reason I did this was to make the code in AssemblyExtensions.GetRoutes() easier to read.
After a few nights of Mtn Dew and convenience-store cherry-pie I finished the rough code, tests and demo project (included in this blog post) and I was starting to realize that:
- Using the attributes is more declaritive and it feels cleaner
- Having your route information right above your actions is incredibly useful
- I had no more need to switch back and forth between your controller and the Global.asax.cs
How does it work?
All of the real work for the RouteAttribute is done in the AssemblyExtensions class. This class uses extension methods to augment the System.Reflection.Assembly class with two methods: GetControllers() and GetRoutes().
GetRoutes is the only method that is used by other classes, I made GetControllers public for unit testing.
GetRoutes()
GetRoutes’ first order of business is to make a list of data that it will need to build out all the routes for the assembly it was passed. After thats done GetRoutes will loop through the collected route data, build up each route and add it to the dictionary that will eventually be returned.
namespace CodeImpossible.Mvc.Routing
{
public static class AssemblyExtensions
{
public static BindingFlags ActionFlags =
BindingFlags.Instance |
BindingFlags.Public |
BindingFlags.DeclaredOnly;
public static IList<ControllerMetaData> GetControllers(this Assembly assembly)
{
var controllers = assembly.GetTypes().ToList().FindAll(type =>
{
var isValidController = type.IsClass &&
type.IsPublic &&
type.IsSubclassOf<Controller>();
var hasValidActions = type.GetMethods(ActionFlags).ToList().Any(m =>
{
var valid = false;
if (m.ReturnParameter != null && m.ReturnParameter.ParameterType == typeof(ActionResult))
{
valid = m.GetAttributesOfType<RouteAttribute>().Count > 0;
}
return valid;
});
return isValidController && hasValidActions;
}).Select<Type, ControllerMetaData>((t) => new ControllerMetaData(t)).ToList();
return controllers;
}
public static IDictionary<string, Route> GetRoutes(this Assembly assembly)
{
var Routes = new Dictionary<string, Route>();
var data = (from c in assembly.GetControllers()
from a in c.GetActions()
from r in a.Data
select new
{
ControllerName = c.Name,
ActionName = a.Name,
RouteData = r,
RouteParams = a.Params
}).ToList();
foreach (var r in data)
{
var route = new Route(r.RouteData.RoutePath, new MvcRouteHandler());
route.Constraints = new RouteValueDictionary();
route.Defaults = new RouteValueDictionary(new {
controller = r.ControllerName,
action = r.ActionName
});
if (r.RouteData.RequireRouteParams && r.RouteParams.Count() == 0)
{
throw new MissingRouteParameterException("Unknown", r.RouteData.RoutePath);
}
var missingParams = new List<ParameterMetaData>();
if (r.RouteData.RequireRouteParams)
{
missingParams = (from p in r.RouteParams
where r.RouteData.RoutePath.IndexOf("{" + p.Name + "}") == -1
select p).ToList();
}
if (missingParams.Count > 0)
{
var param = missingParams.First();
throw new MissingRouteParameterException(param.Name, r.RouteData.RoutePath);
}
foreach (var param in r.RouteParams)
{
if (param.Data != null)
{
if (param.Data.DefaultValue != null)
{
route.Defaults.Add(param.Name, param.Data.DefaultValue);
}
if (param.Data.Constraint != null)
{
route.Constraints.Add(param.Name, param.Data.Constraint);
}
}
}
Routes.Add(r.RouteData.Name ?? r.RouteData.RoutePath, route);
}
return Routes;
}
}
}
Getting the Routes into the RouteTable
Slapping route attributes onto your classes and methods is all well and good but it doesn’t mean anything unless we can get those routes into the RouteTable object easliy. Originally I had the code to add the routes looking something like
var routes = Assembly.GetCurrentExecutingAssembly().GetRoutes();
routes.ForEach(r => RouteTable.Add(r));
This, although pretty easy, wasn’t as readible as I wanted. So I added some extension methods to the RouteTable class:
RouteTable.Routes.IncludeRoutesFromAssembly();
I think both of these are much clearer than doing:
RouteTable.Routes.MapRoute("Root",
"",
new { controller = "Test", action = "GetItem", id = 1 });
RouteTable.Routes.MapRoute("Search",
"Search/{id}",
new { controller = "Test", action = "Search", id = 1 });
//.. SNIP ...
Using the RouteAttribute and RouteParamAttribute
In the controller “TestController” below there are three actions: Index, FindByText, and GetItem. Using the RouteAttribute and RouteParamAttribute makes it pretty clear that the routes for FindByText and GetItem are the same but use different RouteContraints.
So a request for /Test/Search/Hello will go to FindByText while /Test/Search/1 will go to GetItem. Also notice how GetItem has a default value of 2 for the id argument.
public class TestController : Controller
{
[Route(RoutePath = "Test")]
public ActionResult Index()
{
return View();
}
[Route(RoutePath = "Test/Search/{query}")]
public ActionResult FindByText(
[RouteParam(Constraint="[a-zA-Z]{1,}")]
string query)
{
return View();
}
[Route(RoutePath = "Test/Search/{id}")]
public virtual ActionResult GetItem(
[RouteParam(Constraint=@"\d{1,}", DefaultValue=2)]
int id)
{
return View();
}
}There is support for binding multiple routes to the same action; just add another Route attribute:
[Route("Products/Search/{id}")]
[Route("Products/{id}")]
public ActionResult GetProductById(int id)
{
return View();
}
Downsides or things I haven’t gotten to yet
Just some gotchas that I think people might raise issue with.
All of your controllers must inherit from the System.Web.Mvc.Controller class
This isn’t really a big deal because if you are using Asp.net MVC then you really should inherit from the Controller class, but for those of you using FubuMVC or another MVC framework this should be easy to change.
Attributes can be ugly
I know a few people out there are against attributes but I think that this is a more than acceptable use because it made the code much easier to understand.
Reflection can be slow
Honestly, when I first started working on this demo I was sort of turned off by the use of Reflection myself. After weighing the possible performance loss against the gains in both readability and maintenance I decided this was definitely worth it. I haven’t performance tested this code so, as always YMMV.
As always, if I screwed up or there is a better way to do this, please let me know in the comments.
Download the source code mentioned in this blog post.
asp.net · c# · code · MVC · Open Source
Long story short: I hate re-inventing the wheel. If there is a free service that does something I need I will try my hardest to get that service into whatever I am working on. I’m currently working on an Asp .Net MVC project that needs Avatars (you know, those funny little pictures next to peoples names on Twitter). Enter Gravatar.
Gravatar is an awesome service for anyone looking to add avatars to their apps. It’s free, incredibly simple to implement, and removes a lot of the hassle around getting avatar support into your web/windows app.
Adding Gravatar support to an application is pretty simple. Can you get a users email address? Can you MD5 said email address? Can you make an HTTP GET? BANG. You sir, or madam, can have Gravatars.
This week for the W.O.M.M. code sample I’d like to show how I integrated gravatar support into an Asp .Net MVC application.
How Gravatar Works In A Nutshell
Gravatar is a free service where you sign up and link images to one or more email addresses that you provide.
Once you link an image to an email address, any application that supports getting an image over the internet can show your Gravatar by making a request to a special URL. This URL is generated by combining an MD5 hash of your email address with some other parameters and the end result is a link to your Gravatar image.
IE: the link to my Gravatar on the right of this page is:
http://www.gravatar.com/avatar/15559d868ec27b8583f42116a6b96c14?s=140
So 15559d868ec27b8583f42116a6b96c14 is the hash of my email address – don’t worry it’s a one-way hash. The “s” parameter is the size of the image that I want, in this case 140 pixels.
That is pretty much it as far as how the system works, but if you want to read more, check out Gravatar’s implementation documentation.
The Goal
What I wanted was an HtmlHelper extension method that I could use in my view pages to create an IMG tag with the correct Gravatar URL. After looking at the documentation on Gravatars “How the URL is constructed” page, I decided my helper extension should support the following:
Avatar Size (the “s” parameter)
When making a Gravatar URL you can specify a specific size for the Gravatar image. The size can be anything from 1 to 512 pixels, but the default is 80.
Default Avatars (the “d” parameter)
If the email address you are using doesn’t have any Gravatars setup, Gravatar will generate one for you by default. You can choose from 3 predefined Gravatar types or you can include a URL to a custom avatar of your own. The predefined Gravatar types are Identicon, Wavatar, and Monsterid.
Rating (the “r” parameter)
This wasn’t a requirement for what I was working on, but you can designate the maximum “rating” of the avatars that Gravatar will generate. The accepted values are “g”, “pg”, “r”, and “x” and they are inclusive, so specifying “r” will allow “g” and “pg” rated Gravatars to be generated. Gravatars that are rated “x” will be returned as one of the predefined avatars above. The default rating is “g”.
The Code
Okay, so now I know what I need to support. Now it’s just a matter of getting the code to do this. Let’s take a look at the class file I used to get this done.
namespace System.Web.Mvc
{
using System;
using System.Web.Routing;
using System.Web.Security;
public enum GravatarDefaultTypes
{
Identicon,
Wavatar,
Monsterid,
Custom
}
public static class GravatarExtension
{
public static string Gravatar(
this HtmlHelper hh,
string emailAddress,
int size,
GravatarDefaultTypes defaultType,
string customImageUrl,
RouteValueDictionary htmlAttributes)
{
var tagBuilder = new TagBuilder("img");
string url = "http://www.gravatar.com/avatar/{0}?d={1}&s={2}";
// thanks to jon galloway for this one-liner!
// http://www.eggheadcafe.com/aspnet/how-to/141740/adding-gravatars-to-your.aspx
string hash = FormsAuthentication
.HashPasswordForStoringInConfigFile(emailAddress, "MD5");
string defImg = defaultType.ToString().ToLower();
if (defaultType == GravatarDefaultTypes.Custom)
{
defImg = System.Web
.HttpUtility
.UrlEncode(customImageUrl);
}
url = String.Format(
url,
hash.ToLower(),
defImg,
size.ToString());
tagBuilder.MergeAttributes(htmlAttributes);
tagBuilder.MergeAttribute("src", url);
return tagBuilder.ToString(TagRenderMode.Normal);
}
}
}
So you can see I’m not storing the hash of the email address, instead I am going to pass in the unaltered string. I didn’t want to have another piece of data to update when the user changed their email address so the Gravatar() method takes an email address and encodes it using a call to FormsAuthentication.HashPasswordForStoringInConfigFile(), which is awesome ( Thanks Jon, you rock!).
Also, I’m not sure if this is a no-no or what, but I did put the extension class under the System.Web.Mvc namespace. This was mainly a convenience (read: laziness) thing and can be easily changed.
Alright so we have some code now, let’s take a look at how it can be used in our views.
<%= Html.Gravatar(
Model.Email, // the email address
50, // size, in pixels of the avatar
GravatarDefaultTypes.Identicon,
null,
new RouteValueDictionary(new {
style = "vertical-align: middle;"
})
)%>
<%= Model.UserName %>
Let’s see how that looks.
Booyah, avatar support in 55 lines of code. As always, if I screwed up or there is a better way to do this, please let me know.
asp.net · c# · MVC · Open Source
So lately I’ve been working on a project using Asp.net MVC and TDD to build a web 2.0 application. It’s a twitter-like application that I started a while ago but due to my failure to test everything I lost about 99% of my work and had to start over from scratch.
But this was sort of a good thing because it gave me a chance to revisit a lot of things that I wasn’t very happy with the first time around. I just got done adding the ability for users to post new messages via AJAX.
In the first version of the application a user would type their status into a textbox, click submit and the page would refresh with their new message at the top of their user wall. Although functional this wasn’t exactly very “web 2.0″-ish.
My controller will have an action called Index that takes two parameters, the message the users is posting and the tags associated with that message. m_UserService, and m_MessageService are private objects, that interact with the database.
[Authorize]
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Index(string message, string[] tags)
{
var messageOwner = this.m_UserService
.GetByUserName(User.Identity.Name);
var messageObj = new Message()
{
Owner = new User()
{
Identifier = messageOwner.Identifier,
UserName = messageOwner.UserName,
Email = messageOwner.Email,
RealName = messageOwner.RealName,
IsModerator = messageOwner.IsModerator
},
Body = message,
CreatedOn = DateTime.Now,
IsReply = message.StartsWith("@")
};
this.m_MessageService.Post(messageObj);
return Json(messageObj);
}
The JsonResult will be serialized/deserialized by the MVC framework when the code is run in a web project or IIS but I need to be able to test this as part of our build process.
* NOTE: For those of you who might be thinking “how do we get around the authorization”? I’ll answer that in a later post (or you can check out Scott Hanselmans blog for the solution).
Ideally I wanted to do something like the following in my test:
Assert.AreEqual("some text", jsonObject.someproperty);
But since C# is a type-safe language this isn’t easily doable. However, utilizing an extension method and the JavaScriptSerializer in System.Web.Script.Serialization we can come pretty close:
Assert.AreEqual("some text", jsonObject["someproperty"]);
Here is the code I used to achieve this (This code depends on Moq v3.0.108.5 which you can download here):
using System;
using System.Text;
using System.Web;
using System.Web.Script.Serialization;
using System.Web.Mvc;
using Moq;
public static class JsonResultExtensions
{
public static T Deserialize<T>(this JsonResult json,
Controller controller)
{
var jsonSB = new StringBuilder();
var httpResponseMock =
new Mock<httpResponseBase>();
httpResponseMock.Setup(mock => {
mock.Write(It.IsAny<string>());
}).Callback<string>((s) => {
jsonSB.Append(s);
});
var httpContextMock = new Mock<httpContextBase>();
httpContextMock.Setup(mock => mock.Response)
.Returns(httpResponseMock.Object);
controller.ControllerContext
.HttpContext = httpContextMock.Object;
jsonResult.ExecuteResult(
controller.ControllerContext);
return new JavaScriptSerializer()
.Deserialize<T>(jsonSB.ToString());
}
}
asp.net · MVC · Unit Testing
