I have this in my Details View
<tr>
<td>#Html.DisplayNameFor(model => model.ACTION_STATUS):</td>
<td>#Html.DisplayFor(model => model.ACTION_STATUS)</td>
</tr>
How do I apply this:
If ACTION_STATUS == , then display Active Else If ACTION_STATUS ==0, display Inactive, Else Deleted
I suggest using Dictionary instead of if conditions. In this case may seem easy doing an if condition but that is not the right way if there are several branches.
Dictionary<int, string> data = new Dictionary<int, string>();
data.Add(1, "Active");
data.Add(0, "Inactive");
data.Add(-1, "Deleted");
ViewData["data"]=data;
In View you can get them:
#{
var Dictionary = (Dictionary<int, string>)ViewData["data"];
}
and display it as
<td>#Dictionary[model.ACTION_STATUS]</td>
I think this solution is cleaner.
Edit: To address the edit to the question.
I think the best approach, especially now that there are 3 different status options not just 2 is to do the following (as I recommended in my original answer).
1) Create a dictionary similar to Indrit Kello's answer, but make it "static data" somewhere in your project. Maybe it's loaded from a database table of action statuses. Maybe it is something that you load from a config file, or maybe it's just hard-coded in a static class called "Constants.cs" etc. Depends on the situation. If it were hard coded, you might have a class like:
public static class Constants
{
public static Dictionary<int, string> ActionStatuses = new Dictionary<int, string>(){
{ 1, "Active" },
{ 0, "Inactive"},
//etc. Additional statuses go here. No comma on the final entry...
};
}
2) Add a new property to your view model to decode the display text for this status. You can decorate this with attributes etc. as you can normal VM properties so you can continue to use #Html.DisplayFor etc,
public class MyViewModel
{
// Other properties etc...
public string ActionStatusDisplayText { get { return Constants.ActionStatuses[this.ACTION_STATUS]}; }
}
3) Use this new property in your view.
<td>#Html.DisplayFor(model => model.ActionStatusDisplayText)</td>
4) If you have to do this lookup in multiple different view models, you might want to consider moving the lookup code into the Constants class so that you can share the same code with multiple places. Especially true if you need to implement hte case where as tatus might not be in the dictionary for some reason (value = -99 for somereason etc.)
Related
I am working on asp.net mvc3 web application using MS Sql server 2008 express rc2. In my app I have two different brands in DB and one of them have few Null or 'unknown' values (e.g. 'unknown' is added to DB instead of Null). My question is how to pass only non null values to View Engine instead of using If/Else statements in View?
in controller:
var model = _data.GetViewModel(query);
if (model != null)
{
return View(model);
}
else
return View("Error");
in ViewModel;
public int Id { get; set; }
public string Query { get; set; }
public string Brand { get; set; }
public string Family { get; set; }
public string Type { get; set; }
in Model:
public ViewModel GetViewModel(string query)
{
var data = _comp.Get(p => p.Query == query);
if (data == null) return null;
return new ViewModel
{
Id = data.id,
Brand = data.brand,
Family = data.family,
Type = data.type
};
}
in View (I am currently using If statement):
#if (Model.Brand != null)
{
<span class="brand">#Model.Brand</span>
}
#if (Model.Family != null)
{
<span class="family">#Model.Family</span>
}
#if (Model.Type != null)
{
<span class="type">#Model.Type</span>
}
Note: I want to avoid If statement because there are too many values in the Database of each brand, and many of the them are Null, So I don't want to generate Html for those Null values. I am using If/Else statement like above code, and for checking too many values in View using If, it costs Memory on server and processor, and it also slow down server response time.
I want to have an alternative method to do this. Should I use Partial views or anything else?
Please Please help me to solve this, Your help is very appreciated.
Thanks and Regards.
First, some background/context, then my suggestion.
(By the way, this all applies to any version of ASP.NET MVC or ASP.NET NancyFX (yes, there's another option out there!!), etc)
Context / Background
To solve this, people generally fall into two types of categories:
Just get data and let the View decide what to show (common one, not the proper way IMO).
The Controller should handle all the heavy lifting and give the view the exact answer (proper way, IMO).
The first way is quick and dirty. Sure it works, but it puts too much logic into the view. Views are not supposed to do any logic at all (exception: for loops, and maybe the odd if/else, maybe). The main reason for this is testing. Yep, that dirty word which people hate and think it's for hippies only. Or .. I don't have the time to test.. so I manually test, etc.. If you put any business logic into a view, you cannot test that.
The second way might seem a bit slower at first, but that's like anything - the more you practice, the faster you go. This is (IMO) the preferred method of doing things because you can test the controller. The controller should create a view model which will have -the exact- results that the view needs. Not extra. For example, imagine you want to return a list of Brands to the display/view. Most people do (the equivalent of) Get-all-brands into a list, and send that list to the view, even though 80% of those properties are -not- going to be used by that view! Even if ONE property is not going to be used by that view, do not retrieve it nor send it to the view!
So - TL;DR; do all the heavy lifting in the controller. The View is dumb. Just dump the exact view model data, to the view.
Solution to your problem
Ok, so let's roll with idea #2 and get all this stuff happening in the controller.
// Grab the results.
// ASSUMPTION: It is only returning the -exact- data I need. No more, no less.
var results = _data.GetViewModel(query);
if (model == null)
{
// Project the results into a perfectly tight & svelte view model
// 100% specific for this view.
var viewModel = results.
Select(x => new ViewModel
{
Id = x.Id,
Brand = string.IsNullOrEmpty(x.Brand)
? string.Empty
: x.Brand,
Family = string.IsNullOrEmpty(x.Family)
? string.Empty
: x.Family,
Type = string.IsNullOrEmpty(x.Type)
? string.Empty
: x.Type,
}).ToList();
return viewModel;
Testing this..
[Fact]
public void GivenSomeBrands_Index_ReturnsAViewModel()
{
// Arrange.
// NOTE: Our fake repostitory has some fake data. In it ..
// Id: 1, Brand: Gucci.
// Id: 22, Brand: null.
var controller = new BrandController(SomeFakeRepositoryThingy);
// Act.
var result = controller.Index(); // This calls that controller code, above.
// Assert.
Assert.IsNotNull(result); // Controller returned some result.
Assert.IsNotNull(result.Model); // We have some model data.
var model = result.Model as IList<ViewModel>(); // Cast the Model value.
Assert.NotNull(model); // We have a strongly typed view model.
// We check the first brand value.
Assert.Equal("Gucci", model.First().Brand);
// We know this item has a null Brand,
Assert.Equal(string.Empty, model[21].Brand); but the ViewModel converted it.
}
You could write a custom HTML helper:
public static string MyHelper<V>(this HtmlHelper helper, V value, string css)
{
if (value == null)
return "";
return String.Format("<span class='{0}'>{1}</span>", value, css);
}
Then in your view:
#Html.MyHelper(Model.Brand, "brand");
#Html.MyHelper(Model.Family, "family");
#Html.MyHelper(Model.Type, "type");
I've been trying to find a good way to handle the Models of our Asp.net MVC websites when having common properties for all the pages. These properties are to be displayed in the Layout (Master Page). I'm using a "BaseModel" class that holds those properties and my Layout use this BaseModel as its model.
Every other model inherits from that BaseModel and each has specific properties relative to the view it represents. As you might have guessed, my Models are actually View Models even if that's not quite relevant here.
I have tried different ways to initialize the BaseModel values
By "hand" in every view
Having a base controller that has an Initialize virtual method to do it (so specific controller can implement specific common behavior for exemple)
Having a base controlelr that override OnActionExecuting to call the Initialize method
Using a helper class to do it outside of the controller
Using a Model Factory
But none of those really appeal to me:
Seems obvious to me, but DRY is one reason enough to justify that (actually I never tried that solution at all, I'm just putting it to be able to loop on that point in the last point).
I don't like that one because it means that whenever a new Controller is added, you need to know that it has to inherit from the BaseController and that you need to call the Initialize method, not to mention that if your controller has overriden the base one, to call the base anyway to maintain the values.
see next point
and 3. are a variation on the same topic but that doesn't really help with the issues of the second solution.
My favorite so far, but now I have to pass a few more variables to set those values. I like it for the inversion of dependence. But then if I want to provide values from the session, I need to pass them explicitly for exemple, then I'm back to square one as I have to provide them by hand (being references or through an interface of any kind)
Of course, (almost) all of those solutions work, but I'm looking for a better way to do it.
While typing this question, I found maybe a new path, the builder pattern that might also do, but implementations can become quickly a burden too, as we can have dozens of views and controllers.
I'll gladly take any serious recommandation/hint/advice/patterns/suggestion !
Update
Thanks to #EBarr I came up with another solution, using an ActionFilterAttribute (not production code, did it in 5 minutes):
public class ModelAttribute : ActionFilterAttribute
{
public Type ModelType { get; private set; }
public ModelAttribute(string typeName) : this(Type.GetType(typeName)) { }
public ModelAttribute(Type modelType)
{
if(modelType == null) { throw new ArgumentNullException("modelType"); }
ModelType = modelType;
if (!typeof(BaseModel).IsAssignableFrom(ModelType))
{
throw new ArgumentException("model type should inherit BaseModel");
}
}
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
var model = ModelFactory.GetModel(ModelType);
var foo = filterContext.RequestContext.HttpContext.Session["foo"] as Foo;
model.Foo = foo;
model.Bar = somevalue;
filterContext.Controller.TempData["model"] = model;
}
}
Calling it is then really simple:
[Model(typeof(HomeModel))]
public ActionResult Index()
{
var homeModel = TempData["model"] as HomeModel;
// Add View Specific stuff
return View(homeModel);
}
And it gives me the best of every world. The only drawback is to find a proper way to passe the model back to the action.
Here it's done using the TempData object, but I also consider updating the model that one can find in the ActionParameters.
I'm still taking any serious recommandation/hint/advice/patterns/suggestion for that, or the previous points.
I went through almost exactly the same process as I dove into MVC. And you're right, none of the solutions feel that great.
In the end I used a series of base models. For various reasons I had a few different types of base models, but the logic should apply to a single base type. The majority of my view models then inherited from one of the bases. Then, depending on need/timing i fill the base portion of the model in ActionExecuting or OnActionExecuted.
A snippet of my code that should make the process clear:
if (filterContext.ActionParameters.ContainsKey("model")) {
var tempModel = (System.Object)filterContext.ActionParameters["model"];
if (typeof(BaseModel_SuperLight).IsAssignableFrom(tempModel.GetType())) {
//do stuff required by light weight model
}
if (typeof(BaseModel_RegularWeight).IsAssignableFrom(tempModel.GetType())) {
//do more costly stuff for regular weight model here
}
}
In the end my pattern didn't feel too satisfying. It was, however, practical, flexible and easy to implement varying levels of inheritance. I was also able to inject pre or post controller execution, which mattered a lot in my case. Hope this helps.
The idea that gave me #EBarr to use an action filter was actually working but felt wrong in the end, because there was no clean way to retrieve the model without passing through a viewbag, or the httpcontext items, or something alike. Also, it made mandatory to decorate every action with its model. It also made the postback more difficult to handle. I still believe that this solution has merits and might be useful in some specific scenarios.
So I was back to square one and started looking more into that topic. I came to the following. First the problem has two aspects
Initializing the data for the views
Rendering the data
While looking for more idea, I realized that I was not looking at the problem from the right perspective. I was looking at it from a "Controller" POV, whereas the final client for the model is the view. I was also reminded that the Layout/Master page is not a view and should not have a model associated with it. That insight put me on what feels the right path for me. Because it meant that every "dynamic" part of the Layout should be handled outside of it. Of course, sections seems the perfect fit for that, because of their flexibility.
On the test solution I made, I had (only) 4 different sections, some mandatory, some not. The problem with sections, is that you need to add them on every page, which can quickly be a pain to update/modify. To solve that, I tried this:
public interface IViewModel
{
KeyValuePair<string, PartialViewData>[] Sections { get; }
}
public class PartialViewData
{
public string PartialViewName { get; set; }
public object PartialViewModel { get; set; }
public ViewDataDictionary ViewData { get; set; }
}
For exemple, my model for the view is this:
public class HomeViewModel : IViewModel
{
public Article[] Articles { get; set; } // Article is just a dummy class
public string QuickContactMessage { get; set; } // just here to try things
public HomeViewModel() { Articles = new Article[0]; }
private Dictionary<string, PartialViewData> _Sections = new Dictionary<string, PartialViewData>();
public KeyValuePair<string, PartialViewData>[] Sections
{
get { return _Sections.ToArray(); }
set { _Sections = value.ToDictionary(item => item.Key, item => item.Value); }
}
}
This get initialized in the action:
public ActionResult Index()
{
var hvm = ModelFactory.Get<HomeViewModel>(); // Does not much, basicaly a new HomeViewModel();
hvm.Sections = LayoutHelper.GetCommonSections().ToArray(); // more on this just after
hvm.Articles = ArticlesProvider.GetArticles(); // ArticlesProvider could support DI
return View(hvm);
}
LayoutHelper is a property on the controller (which could be DI'ed if needed):
public class DefaultLayoutHelper
{
private Controller Controller;
public DefaultLayoutHelper(Controller controller) { Controller = controller; }
public Dictionary<string, PartialViewData> GetCommonSections(QuickContactModel quickContactModel = null)
{
var sections = new Dictionary<string, PartialViewData>();
// those calls were made in methods in the solution, I removed it to reduce the length of the answer
sections.Add("header",
Controller.UserLoggedIn() // simple extension that check if there is a user logged in
? new PartialViewData { PartialViewName = "HeaderLoggedIn", PartialViewModel = new HeaderLoggedInViewModel { Username = "Bishop" } }
: new PartialViewData { PartialViewName = "HeaderNotLoggedIn", PartialViewModel = new HeaderLoggedOutViewModel() });
sections.Add("quotes", new PartialViewData { PartialViewName = "Quotes" });
sections.Add("quickcontact", new PartialViewData { PartialViewName = "QuickContactForm", PartialViewModel = model ?? new QuickContactModel() });
return sections;
}
}
And in the views (.cshtml):
#section quotes { #{ Html.RenderPartial(Model.Sections.FirstOrDefault(s => s.Key == "quotes").Value); } }
#section login { #{ Html.RenderPartial(Model.Sections.FirstOrDefault(s => s.Key == "header").Value); } }
#section footer { #{ Html.RenderPartial(Model.Sections.FirstOrDefault(s => s.Key == "footer").Value); } }
The actual solution has more code, I tried to simplify to just get the idea here. It's still a bit raw and need polishing/error handling, but with that I can define in my action, what the sections will be, what model they will use and so on. It can be easily tested and setting up DI should not be an issue.
I still have to duplicate the #section lines in every view, which seems a bit painful (especialy because we can't put the sections in a partial view).
I'm looking into the templated razor delegates to see if that could not replace the sections.
There is a field in our database which really ought to be a boolean, but for some reason the original developers made it a CHAR which will either be set to "1" or "0".
[Column("CHARGEABLE")]
[StringLength(1)]
private string Chargeable { get; set; }
I want my model to represent this field as a boolean so I figured I could add a property to my model to wrap it:
[NotMapped]
public bool ChargeableTrue
{
get
{
return Chargeable == "1" ? true : false;
}
set
{
Chargeable = value ? "1" : "0";
}
}
Now on my View I just display the EditorFor ( ChargeableTrue ), but when I click save it doesn't actually update it.
I think what is happening is that when the model is being updated, it's still attempting to get the value of 'Chargeable' from the View, even though I haven't displayed it there. And since there is no input field, it just gets null and ends up saving that to the database.
if (ModelState.IsValid)
{
db.Entry(call).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
What is one expected to do in this situation?
Based on KMan's answer, here's the extended version just in case you're not familiar with creating view models.
The idea is that your domain object is not really what you want to be updating exactly from your views. Instead, you create a go-between that can also include view-specific items (like a list of objects to populate a drop-down).
public class MyViewModel {
public bool Chargeable { get; set; }
}
Now you can do this:
#* In view *#
Html.EditorFor(m => m.Chargeable)
// In controller
public ActionResult Save(MyViewModel model) {
if (ModelState.IsValid) {
var domainObject = new MyObject() {
Chargeable = model.Chargeable ? "1" : "0"
};
// the rest of your code using domainObject
}
}
I'd consider just creating an overload of your domain object's constructor that accepts your view model to keep the mapping in one place. I typically use a tool like AutoMapper to map objects or manual extension methods.
A view model typically contains a sub-set of your domain object's properties, but can contain all of them or more properties like lists, visbility states, etc. They come in incredibly useful and I've never done a MVC project where I haven't used them.
Use a view model and make your mapping on the controller.
My current problem is that I have a partial view that I want to determine what model is being used by it.
I have had to deal with a few strange scenarios for my project so I will try to outline it here, maybe someone can offer a better way to do this.
I am designing something like the Google iGoogle page. A main page with multiple widgets that are able to move around or be configured as needed. The current system loads the actual widget's data asynchronously view a POST to a controller within my application. That controller will either render a partial view to HTML that can be returned (and then loaded into the page view JQUERY) or just straight HTML/JavaScript that is stored in a database.
This was working fine for me, I had a model for the widgets that holds a dictionary of options that are described via the database, and then used by the partial view. The problem came when I wanted to pass data to a partial view. The best solution I could come up with was having the controller determine which model the partial view in question uses, have some function that will fill the model, and then pass it, along with the partial view, to the function that will render it to HTML within the controller.
I realize this is an odd scenario for MVC (the layers are blending...) and any advice on fundamental design, or implementation of this would be greatly appreciated.
I am currently using MVC3/Razor. Feel free to ask any other questions.
I prototyped a possible solution to this, because it seemed like a fun problem. I hope it's useful to you.
Models
First, the models. I decided to create two 'widgets', one for news, and one for a clock.
public class NewsModel
{
public string[] Headlines { get; set; }
public NewsModel(params string[] headlines)
{
Headlines = headlines;
}
}
public class ClockModel
{
public DateTime Now { get; set; }
public ClockModel(DateTime now)
{
Now = now;
}
}
Controller
My controller doesn't know anything about the views. What it does is returns a single model, but that model has the ability to dynamically fetch the right model as required by the view.
public ActionResult Show(string widgetName)
{
var selector = new ModelSelector();
selector.WhenRendering<ClockModel>(() => new ClockModel(DateTime.Now));
selector.WhenRendering<NewsModel>(() => new NewsModel("Headline 1", "Headline 2", "Headline 3"));
return PartialView(widgetName, selector);
}
Delegates are used so that the correct model is only created/fetched if it is actually used.
ModelSelector
The ModelSelector that the controller uses is pretty simple - it just keeps a bag of delegates to create each model type:
public class ModelSelector
{
private readonly Dictionary<Type, Func<object>> modelLookup = new Dictionary<Type, Func<object>>();
public void WhenRendering<T>(Func<object> getter)
{
modelLookup.Add(typeof(T), getter);
}
public object GetModel(Type modelType)
{
if (!modelLookup.ContainsKey(modelType))
{
throw new KeyNotFoundException(string.Format("A provider for the model type '{0}' was not provided", modelType.FullName));
}
return modelLookup[modelType]();
}
}
The Views - Simple solution
Now, the easiest way to implement a view would be:
#model MvcApplication2.ModelSelector
#using MvcApplication2.Models
#{
var clock = (ClockModel) Model.GetModel(typeof (ClockModel));
}
<h2>The time is: #clock.Now</h2>
You could end here and use this approach.
The Views - Better solution
That's pretty ugly. I wanted my views to look like this:
#model MvcApplication2.Models.ClockModel
<h2>Clock</h2>
#Model.Now
And
#model MvcApplication2.Models.NewsModel
<h2>News Widget</h2>
#foreach (var headline in Model.Headlines)
{
<h3>#headline</h3>
}
To make this work, I had to create a custom view engine.
Custom view engine
When a Razor view is compiled, it inherits a ViewPage<T>, where T is the #model. So we can use reflection to figure out what type the view wanted, and select it.
public class ModelSelectorEnabledRazorViewEngine : RazorViewEngine
{
protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
{
var result = base.CreateView(controllerContext, viewPath, masterPath);
if (result == null)
return null;
return new CustomRazorView((RazorView) result);
}
protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
{
var result = base.CreatePartialView(controllerContext, partialPath);
if (result == null)
return null;
return new CustomRazorView((RazorView)result);
}
public class CustomRazorView : IView
{
private readonly RazorView view;
public CustomRazorView(RazorView view)
{
this.view = view;
}
public void Render(ViewContext viewContext, TextWriter writer)
{
var modelSelector = viewContext.ViewData.Model as ModelSelector;
if (modelSelector == null)
{
// This is not a widget, so fall back to stock-standard MVC/Razor rendering
view.Render(viewContext, writer);
return;
}
// We need to work out what #model is on the view, so that we can pass the correct model to it.
// We can do this by using reflection over the compiled views, since Razor views implement a
// ViewPage<T>, where T is the #model value.
var compiledViewType = BuildManager.GetCompiledType(view.ViewPath);
var baseType = compiledViewType.BaseType;
if (baseType == null || !baseType.IsGenericType)
{
throw new Exception(string.Format("When the view '{0}' was compiled, the resulting type was '{1}', with base type '{2}'. I expected a base type with a single generic argument; I don't know how to handle this type.", view.ViewPath, compiledViewType, baseType));
}
// This will be the value of #model
var modelType = baseType.GetGenericArguments()[0];
if (modelType == typeof(object))
{
// When no #model is set, the result is a ViewPage<object>
throw new Exception(string.Format("The view '{0}' needs to include the #model directive to specify the model type. Did you forget to include an #model line?", view.ViewPath));
}
var model = modelSelector.GetModel(modelType);
// Switch the current model from the ModelSelector to the value of #model
viewContext.ViewData.Model = model;
view.Render(viewContext, writer);
}
}
}
The view engine is registered by putting this in Global.asax.cs:
ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(new ModelSelectorEnabledRazorViewEngine());
Rendering
My home view includes the following lines to test it all out:
#Html.Action("Show", "Widget", new { widgetName = "Clock" })
#Html.Action("Show", "Widget", new { widgetName = "News" })
One option would be to extend the idea of partial requests in your application. Steve Sanderson has a fantastic example of this, although the post relates to MVC 1 & 2. I think it would still help in you v3, but I haven't investigated v3 to see if the MVC team implemented their own version. In your asynch scenario, you'll need to toy with the implementation a bit, perhaps change the PartialRequest definition to accept different information as needed, but I think this might be a good start. The net result would be better isolation of concerns, allowing individual controllers to manage a particular type of partial, and in turn be better aware of the model Type you want to work with.
I'm not 100% sure that this is what you'd be looking for, but the [ChildActionOnly] attribute can be added to a method within your controller. That requires that the method can only be called from a partial view. Then you can set up your partial view for that method that basically resembles one of your widgets. Check out the MVC Music Store example here:
http://www.asp.net/mvc/tutorials/mvc-music-store-part-10
What about a dynamic view model? Layouts in MVC3 use them, and maybe you can use something similar for your purposes:
Dynamic in C# 4.0: Introducing the ExpandoObject
Fun With Method Missing and C# 4
Dynamic View Page, MVC without a View Model
I blogged about doing exactly this. Please see http://blogs.planetcloud.co.uk/mygreatdiscovery/?tag=/widget
Essentially I built out a similar widget system. The posts also cover how to handle configuration of those widgets. This makes use of the dynamic support in Mvc3 so that any model object can be passed to the view, from a single controller action.
By default all widgets have a collection of KVP properties (I believe this is what the OP has). So for a simple widget we get access to those properties from within the view. I used for a widget that displayed some html (where the html was stored in one of those properties).
However, for more complex widgets we implement IWidgetWithDisplayModel. This tells us that before we pass the loaded widget back to the view, we need to "build" our display model.
Here's the controller action that does that. Check the posts for full details.
[HttpGet]
public ActionResult Get(string name)
{
var widget = widgetService.GetWidgetBySystemName(name, true);
if (widget == null)
return Content(string.Format("Widget [{0}] not found!", name));
if (!this.ViewExists(widget.WidgetName))
return Content(string.Format("A template for widget [{0}] was not found.", widget.WidgetName));
if (widget is IWidgetWithDisplayModel) {
(widget as IWidgetWithDisplayModel).CreateDisplayModel();
}
return PartialView(widget.WidgetName, widget);
}
I have an enum for one of the properties of my view-model. I want to display a drop-down list that contains all the values of the enum. I can get this to work with the following code.
What I'm wondering is whether there is a simple way to convert from an enum to an IEnumerable? I can do it manually as in the following example, but when I add a new enum value the code breaks. I imagine that I can do it via reflection as per this example, but but are there other ways to do this?
public enum Currencies
{
CAD, USD, EUR
}
public ViewModel
{
[Required]
public Currencies SelectedCurrency {get; set;}
public SelectList Currencies
{
List<Currencies> c = new List<Currencies>();
c.Add(Currencies.CAD);
c.Add(Currencies.USD);
c.Add(Currencies.EUR);
return new SelectList(c);
}
}
I'm using a helper that i found here to populate my SelectLists with a generic enum type, i did a little modification to add the selected value though, here's how it looks like :
public static SelectList ToSelectList<T>(this T enumeration, string selected)
{
var source = Enum.GetValues(typeof(T));
var items = new Dictionary<object, string>();
var displayAttributeType = typeof(DisplayAttribute);
foreach (var value in source)
{
FieldInfo field = value.GetType().GetField(value.ToString());
DisplayAttribute attrs = (DisplayAttribute)field.
GetCustomAttributes(displayAttributeType, false).FirstOrDefault()
items.Add(value, attrs != null ? attrs.GetName() : value.ToString());
}
return new SelectList(items, "Key", "Value", selected);
}
The nice thing about it is that it reads the DisplayAttribute as the title rather than the enum name. (if your enums contain spaces or you need localization then it makes your life much easier)
So you will need to add the Display attirubete to your enums like this :
public enum User_Status
{
[Display(Name = "Waiting Activation")]
Pending, // User Account Is Pending. Can Login / Can't participate
[Display(Name = "Activated" )]
Active, // User Account Is Active. Can Logon
[Display(Name = "Disabled" )]
Disabled, // User Account Is Diabled. Can't Login
}
and this is how you use them in your views.
<%: Html.DropDownList("ChangeStatus" , ListExtensions.ToSelectList(Model.statusType, user.Status))%>
Model.statusType is just an enum object of type User_Status.
That's it , no more SelectLists in your ViewModels. In my example I'm refrencing an enum in my ViewModel but you can Refrence the enum type directly in your view though. I'm just doing it to make everything clean and nice.
Hope that was helpful.
Look at Enum.GetNames(typeof(Currencies))
I am very late on this one but I just found a really cool way to do this with one line of code, if you are happy to add the Unconstrained Melody NuGet package (a nice, small library from Jon Skeet).
This solution is better because:
It ensures (with generic type constraints) that the value really is an enum value (due to Unconstrained Melody)
It avoids unnecessary boxing (due to Unconstrained Melody)
It caches all the descriptions to avoid using reflection on every call (due to Unconstrained Melody)
It is less code than the other solutions!
So, here are the steps to get this working:
In Package Manager Console, "Install-Package UnconstrainedMelody"
Add a property on your model like so:
//Replace "YourEnum" with the type of your enum
public IEnumerable<SelectListItem> AllItems
{
get
{
return Enums.GetValues<YourEnum>().Select(enumValue => new SelectListItem { Value = enumValue.ToString(), Text = enumValue.GetDescription() });
}
}
Now that you have the List of SelectListItem exposed on your model, you can use the #Html.DropDownList or #Html.DropDownListFor using this property as the source.
So many good answers - I thought I'sd add my solution - I am building the SelectList in the view (and not in the Controller):
In my c#:
namespace ControlChart.Models
//My Enum
public enum FilterType {
[Display(Name = "Reportable")]
Reportable = 0,
[Display(Name = "Non-Reportable")]
NonReportable,
[Display(Name = "All")]
All };
//My model:
public class ChartModel {
[DisplayName("Filter")]
public FilterType Filter { get; set; }
}
In my cshtml:
#using System.ComponentModel.DataAnnotations
#using ControlChart.Models
#model ChartMode
#*..........*#
#Html.DropDownListFor(x => x.Filter,
from v in (ControlChart.Models.FilterType[])(Enum.GetValues(typeof(ControlChart.Models.FilterType)))
select new SelectListItem() {
Text = ((DisplayAttribute)(typeof(FilterType).GetField(v.ToString()).GetCustomAttributes(typeof(DisplayAttribute), false).First())).Name,
Value = v.ToString(),
Selected = v == Model.Filter
})
HTH
Maybe is too late, but i think it could be useful for people with the same problem.
I've found here that now with MVC 5 it's included an EnumDropDownListFor html helper that makes for no longer necesary the use of custom helpers or other workarounds.
In this particular case, just add this:
#Html.EnumDropDownListFor(x => x.SelectedCurrency)
and that's all!
You can also translate or change the displayed text via data annotations and resources files:
Add the following data annotations to your enum:
public enum Currencies
{
[Display(Name="Currencies_CAD", ResourceType=typeof(Resources.Enums)]
CAD,
[Display(Name="Currencies_USD", ResourceType=typeof(Resources.Enums)]
USD,
[Display(Name="Currencies_EUR", ResourceType=typeof(Resources.Enums)]
EUR
}
Create the corresponding resources file.