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Views returned based on variable and existence

I have an asp.net-mvc website I am working on. The site is meant to as a basis for multiple clients all with their own unique business requirements. For any given controller method, I may or may not have a customized view for the client based on their ClientId.
Right now how I am handling this is through a ResourceSelectorObject like so:
public class ClientResourceSelector
{
public ClientResourceSelector(int clientId)
{
this.ClientId = clientId;
}
public int ClientId { get; set; }
public readonly List<ViewProfile> ViewProfiles = new List<ViewProfile>()
{
new ViewProfile { ClientId = 8, Controller = "Contact", Action = "NewContact", View = "C008/NewContact" }
};
public string ViewName(string controller, string action)
{
var Profile = ViewProfiles.FirstOrDefault(X => X.Controller.Equals(controller) && X.Action.Equals(action) && X.ClientId == ClientId);
if (Profile == null) return string.Empty;
return Profile.View;
}
}
Then in the code, I use that object in this manner:
// GET: Contact/NewContact
public ActionResult NewContact()
{
var selector = new ClientResourceSelector(ClientId);
string alternate_view = selector.ViewName("Contact", "NewContact");
if (String.IsNullOrEmpty(alternate_view))
return View(NewContactViewModel.Instance(ClientId));
else
return View(alternate_view, NewContactViewModel.Instance(ClientId));
}
The problem, and this is definitely the programming equivalent of "First World Problems," but I would like to still be able to just call View(viewModel) and have it select the appropriate view to display programmatically without my having to remember to register each view in the selector.
Obviously, I would then want to override the View() method in the abstract controller that all of my controllers are inheriting from. But I am unsure of how that code would look. Any suggestions would be helpful.

Here is how I've created ones in the past. Most of the Tenant systems I've built use some type of route/request parameter (could easily be updated to use DNS or wahtever, you have a lot of options) to determine the specific Tenant. I use an action filter that executes before any controller (or routing) to populate the route data (useful for Tenant specific routes as well).
public class TenantActionFilterAttribute : ActionFilterAttribute
{
internal const string _Tenant = "tenant";
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
// Do this how ever you want, right now I'm using querystring
// Could be changed to use DNS name or whatever
var tenant = filterContext.HttpContext.Request.QueryString[_Tenant] as string;
if (tenant != null)
{
filterContext.RouteData.Values[Tenant] = tenant;
}
}
}
Either globally register the action filter:
RegisterGlobalFilters(GlobalFilters.Filters);
(Or using a Dependency Injection Framework)
Then a custom ViewEngine:
public class TenantViewEngine : RazorViewEngine
{
private string GetPrefix(ControllerContext controllerContext)
{
var result = string.Empty;
var tenant = controllerContext.RouteData.Values[TenantActionFilterAttribute.Tenant] as string;
if (!string.IsNullOrEmpty(tenant))
{
result = "Tenants/" + tenant + "/";
}
return result;
}
protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
{
var prefix = GetPrefix(controllerContext);
if (partialPath.StartsWith("~/"))
{
partialPath = partialPath.Insert(2, prefix);
}
else if (partialPath.StartsWith("~") || partialPath.StartsWith("/"))
{
partialPath = partialPath.Insert(1, prefix);
}
else if (string.IsNullOrEmpty(partialPath))
{
partialPath = prefix + partialPath;
}
return base.CreatePartialView(controllerContext, partialPath);
}
protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
{
var prefix = GetPrefix(controllerContext);
if (viewPath.StartsWith("~/"))
{
viewPath = viewPath.Insert(2, prefix);
}
else if (viewPath.StartsWith("~") || viewPath.StartsWith("/"))
{
viewPath = viewPath.Insert(1, prefix);
}
else if (!string.IsNullOrEmpty(viewPath))
{
viewPath = prefix + viewPath;
}
if (masterPath.StartsWith("~/"))
{
masterPath = masterPath.Insert(2, prefix);
}
else if (masterPath.StartsWith("~") || masterPath.StartsWith("/"))
{
masterPath = masterPath.Insert(1, prefix);
}
else if (!string.IsNullOrEmpty(masterPath))
{
masterPath = prefix + masterPath;
}
return base.CreateView(controllerContext, viewPath, masterPath);
}
}
I can't exactly remember how this works, but the search paths change from the default to something very close to:
"~/Tenants/<TenantName>/Areas/{3}/Views/{1}/{0}.cshtml",
"~/Areas/{3}/Views/{1}/{0}.cshtml",
"~/Tenants/<TenantName>//Views/{1}/{0}.cshtml",
"~/Views/{1}/{0}.cshtml",
"~/Tenants/<TenantName>//Views/Shared/{0}.cshtml",
"~/Views/Shared/{0}.cshtml",
Where 1:Controller, 2:View/Action, 3:AreaName

Typeahead.js for MVC 5 Models

Ive just imlemented typeahead functionality using thw Typeahead.js for MVC 5 Models wrapper
http://timdwilson.github.io/typeahead-mvc-model/
it all works ok but i just cant figure out how to set the limit on the number of items displayed in the suggestion drop down. the javascript would be this
$('#scrollable-dropdown-menu .typeahead').typeahead(null, {
name: 'countries',
limit: 10, -----> limit set here
source: countries
});
but I cant see how the mvc models wrapper implements this, there are three overloads and one of the has 'AdditionalViewdata' maybe this is whats needed ? There is no documentation that I can find and no one else seems to have done this (it looks like it defaults to 5 in the dropdown) My backend mechanism IS returning more than 5 results, its just not being reflected in the html
#Html.AutocompleteFor(model => model.Organisation.Org, model => model.Organisation.ORGID, "Autocomplete", "Organisation", false, new { htmlAttributes = new { #class = "form-control" } })
can anyone help ?

The key is to use the linq "Take"
This works: 1) Create an action in your controller and set the RouteConfig to start this action
public class HomeController : Controller
{
public ActionResult Index20()
{
MyViewModel m = new MyViewModel();
return View(m);
}
Create a view without any type of master page
Add this view model:
public class MyViewModel
{
public string SourceCaseNumber { get; set; }
}
Go to Manage Nuget Packages or PM Console and add to MVC 5 project - Typeahead.js for MVC 5 Models by Tim Wilson
Change the namespace for the added HtmlHelpers.cs to System.Web.Mvc.Html and rebuild
Add this class:
public class CasesNorm
{
public string SCN { get; set; }
}
Add these methods to your controller:
private List<Autocomplete> _AutocompleteSourceCaseNumber(string query)
{
List<Autocomplete> sourceCaseNumbers = new List<Autocomplete>();
try
{
//You will goto your Database for CasesNorm, but if will doit shorthand here
//var results = db.CasesNorms.Where(p => p.SourceCaseNumber.Contains(query)).
// GroupBy(item => new { SCN = item.SourceCaseNumber }).
// Select(group => new { SCN = group.Key.SCN }).
// OrderBy(item => item.SCN).
// Take(10).ToList(); //take 10 is important
CasesNorm c1 = new CasesNorm { SCN = "11111111"};
CasesNorm c2 = new CasesNorm { SCN = "22222222"};
IList<CasesNorm> aList = new List<CasesNorm>();
aList.Add(c1);
aList.Add(c2);
var results = aList;
foreach (var r in results)
{
// create objects
Autocomplete sourceCaseNumber = new Autocomplete();
sourceCaseNumber.Name = string.Format("{0}", r.SCN);
sourceCaseNumber.Id = Int32.Parse(r.SCN);
sourceCaseNumbers.Add(sourceCaseNumber);
}
}
catch (EntityCommandExecutionException eceex)
{
if (eceex.InnerException != null)
{
throw eceex.InnerException;
}
throw;
}
catch
{
throw;
}
return sourceCaseNumbers;
}
public ActionResult AutocompleteSourceCaseNumber(string query)
{
return Json(_AutocompleteSourceCaseNumber(query), JsonRequestBehavior.AllowGet);
}
throw;
}
catch
{
throw;
}
return sourceCaseNumbers;
}
public ActionResult AutocompleteSourceCaseNumber(string query)
{
return Json(_AutocompleteSourceCaseNumber(query), JsonRequestBehavior.AllowGet);
}
credit goes to http://timdwilson.github.io/typeahead-mvc-model/

How do I implement a custom RazorViewEngine to find views in non-standard locations?

I'm looking at implementing a custom RazorViewEngine. Basically I have two sites with effectively the same code base. The differences being that they look different. I want to override the standard view engine to make MVC look in two separate locations for it's views, layouts, etc. one for company A and another for Company B. Company A will contain the master views and company B's view will override these masters. So I want the View Engine to look in location B for a view, layout, master or partial if it finds it then return it, if it doesn't find it I want it to default to company A's views as the default. Obviously company A will only look in it's own folder.
Ok to the crux of the question:
I've found this site: http://www.aspnetwiki.com/mvc-3-razor:extending-the-view-engine
First question, is this the best way to achieve this?
Second do I need to override the CreatePartial, CreateView, FindPartial and FindView methods?
Update
Ok I've figured out the second question myself, the Methods I want to override are CreateView and CreatePartialView as at this point it's built the view string and I can fiddle with it.

Ok in the end I opted for an approach detailed here: http://weblogs.asp.net/imranbaloch/archive/2011/06/27/view-engine-with-dynamic-view-location.aspx
thanks to #Adriano for the answers and pointers but in the end I think this approach fits my needs better. The approach below allows me to keep the standard functionality but to create a new higher priority view location to be searched.
public class Travel2ViewEngine : RazorViewEngine
{
protected BrandNameEnum BrandName;
private string[] _newAreaViewLocations = new string[] {
"~/Areas/{2}/%1Views/{1}/{0}.cshtml",
"~/Areas/{2}/%1Views/{1}/{0}.vbhtml",
"~/Areas/{2}/%1Views//Shared/{0}.cshtml",
"~/Areas/{2}/%1Views//Shared/{0}.vbhtml"
};
private string[] _newAreaMasterLocations = new string[] {
"~/Areas/{2}/%1Views/{1}/{0}.cshtml",
"~/Areas/{2}/%1Views/{1}/{0}.vbhtml",
"~/Areas/{2}/%1Views/Shared/{0}.cshtml",
"~/Areas/{2}/%1Views/Shared/{0}.vbhtml"
};
private string[] _newAreaPartialViewLocations = new string[] {
"~/Areas/{2}/%1Views/{1}/{0}.cshtml",
"~/Areas/{2}/%1Views/{1}/{0}.vbhtml",
"~/Areas/{2}/%1Views/Shared/{0}.cshtml",
"~/Areas/{2}/%1Views/Shared/{0}.vbhtml"
};
private string[] _newViewLocations = new string[] {
"~/%1Views/{1}/{0}.cshtml",
"~/%1Views/{1}/{0}.vbhtml",
"~/%1Views/Shared/{0}.cshtml",
"~/%1Views/Shared/{0}.vbhtml"
};
private string[] _newMasterLocations = new string[] {
"~/%1Views/{1}/{0}.cshtml",
"~/%1Views/{1}/{0}.vbhtml",
"~/%1Views/Shared/{0}.cshtml",
"~/%1Views/Shared/{0}.vbhtml"
};
private string[] _newPartialViewLocations = new string[] {
"~/%1Views/{1}/{0}.cshtml",
"~/%1Views/{1}/{0}.vbhtml",
"~/%1Views/Shared/{0}.cshtml",
"~/%1Views/Shared/{0}.vbhtml"
};
public Travel2ViewEngine()
: base()
{
Enum.TryParse<BrandNameEnum>(Travel2.WebUI.Properties.Settings.Default.BrandName, out BrandName);
AreaViewLocationFormats = AppendLocationFormats(_newAreaViewLocations, AreaViewLocationFormats);
AreaMasterLocationFormats = AppendLocationFormats(_newAreaMasterLocations, AreaMasterLocationFormats);
AreaPartialViewLocationFormats = AppendLocationFormats(_newAreaPartialViewLocations, AreaPartialViewLocationFormats);
ViewLocationFormats = AppendLocationFormats(_newViewLocations, ViewLocationFormats);
MasterLocationFormats = AppendLocationFormats(_newMasterLocations, MasterLocationFormats);
PartialViewLocationFormats = AppendLocationFormats(_newPartialViewLocations, PartialViewLocationFormats);
}
private string[] AppendLocationFormats(string[] newLocations, string[] defaultLocations)
{
List<string> viewLocations = new List<string>();
viewLocations.AddRange(newLocations);
viewLocations.AddRange(defaultLocations);
return viewLocations.ToArray();
}
protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
{
return base.CreateView(controllerContext, viewPath.Replace("%1", BrandName.ToString()), masterPath);
}
protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
{
return base.CreatePartialView(controllerContext, partialPath.Replace("%1", BrandName.ToString()));
}
protected override bool FileExists(ControllerContext controllerContext, string virtualPath)
{
return base.FileExists(controllerContext, virtualPath.Replace("%1", BrandName.ToString()));
}
}
then register in Gloabal.asax
protected void Application_Start(object sender, EventArgs e)
{
RegisterRoutes(RouteTable.Routes);
//Register our customer view engine to control T2 and TBag views and over ridding
ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(new Travel2ViewEngine());
}

Yes that's the way but you do not need to override that methods. RazorViewEngine inherits from VirtualPathProviderViewEngine so you can use its properties to set the location of your views.
For an example read Creating your first MVC ViewEngine and How to set a Default Route (To an Area) in MVC.

Here's my answer:
Add this to your global.ascx
ViewEngines.Engines.Clear();
var customEngine = new RazorViewEngine();
customEngine.PartialViewLocationFormats = new string[]
{
"~/Views/{1}/{0}.cshtml",
"~/Views/Shared/{0}.cshtml",
"~/Views/Partial/{0}.cshtml",
"~/Views/Partial/{1}/{0}.cshtml"
};
customEngine.ViewLocationFormats = new string[]
{
"~/Views/{1}/{0}.cshtml",
"~/Views/Shared/{0}.cshtml",
"~/Views/Controller/{1}/{0}.cshtml"
};
customEngine.MasterLocationFormats = new string[]
{
"~/Views/Shared/{0}.cshtml",
"~/Views/Layout/{0}.cshtml"
};
ViewEngines.Engines.Add(customEngine);
those are the folders where razor checks your views.
Let me know if this works.

Using the Razor view engine in a different way

I thought it would be interesting if I could use the new MVC Razor View engine as a mail merge technology. It can still be part of an MVC website and does not have to be stand-alone console app.
Example:
string myTemplate = "Hello #Name, How are you today?";
ViewModel.Name = "Billy Boy";
string output = RazorViewEngineRender( myTemplate, ViewModel );
Then the string output = "Hello Billy Boy, How are you today?"
The main thing is I want the template to be driven from a string rather than a view or partialview.
Does anyone know if this is possible ?
UPDATE:
Ben and Matt made a project on codeplex: http://razorengine.codeplex.com/

Warning
This is some ugly ugly code that was hacked together without testing it other than getting it to work properly.
VirtualPathProvider
Since we're not dealing with actual views on the server we have to add our own path provider to tell MVC where to get our dynamically generated templates. There should be more tests like checking the strings Dictionary to see if the view has been added.
public class StringPathProvider : VirtualPathProvider {
public StringPathProvider()
: base() {
}
public override CacheDependency GetCacheDependency(string virtualPath, IEnumerable virtualPathDependencies, DateTime utcStart) {
return null;
}
public override bool FileExists(string virtualPath) {
if (virtualPath.StartsWith("/stringviews") || virtualPath.StartsWith("~/stringviews"))
return true;
return base.FileExists(virtualPath);
}
public override VirtualFile GetFile(string virtualPath) {
if (virtualPath.StartsWith("/stringviews") || virtualPath.StartsWith("~/stringviews"))
return new StringVirtualFile(virtualPath);
return base.GetFile(virtualPath);
}
public class StringVirtualFile : System.Web.Hosting.VirtualFile {
string path;
public StringVirtualFile(string path)
: base(path) {
//deal with this later
this.path = path;
}
public override System.IO.Stream Open() {
return new System.IO.MemoryStream(System.Text.ASCIIEncoding.ASCII.GetBytes(RazorViewEngineRender.strings[System.IO.Path.GetFileName(path)]));
}
}
}
Render Class
This class takes your template as a constructor parameter and adds it to a static Dictionary that is then read by the VirtualPathProvider above. You then call Render and you can optionally pass in a model. This will add the fully qualified model type to the #inherits and prepend that to the file contents.
public class RazorViewEngineRender {
internal static Dictionary<string, string> strings { get; set; }
string guid;
static RazorViewEngineRender() {
strings = new Dictionary<string, string>();
}
public RazorViewEngineRender(string Template) {
guid = Guid.NewGuid().ToString() + ".cshtml";
strings.Add(guid, Template);
}
public string Render() {
return Render(null);
}
public string Render(object ViewModel) {
//Register model type
if (ViewModel == null) {
strings[guid] = "#inherits System.Web.Mvc.WebViewPage\r\n" + strings[guid];
} else {
strings[guid] = "#inherits System.Web.Mvc.WebViewPage<" + ViewModel.GetType().FullName + ">\r\n" + strings[guid];
}
CshtmlView view = new CshtmlView("/stringviews/" + guid);
System.Text.StringBuilder sb = new System.Text.StringBuilder();
System.IO.TextWriter tw = new System.IO.StringWriter(sb);
ControllerContext controller = new ControllerContext();
ViewDataDictionary ViewData = new ViewDataDictionary();
ViewData.Model = ViewModel;
view.Render(new ViewContext(controller, view, ViewData, new TempDataDictionary(), tw), tw);
//view.ExecutePageHierarchy();
strings.Remove(guid);
return sb.ToString();
}
}
Global.asax
In your global.asax file you'll have to add the following to the Application_Start
System.Web.Hosting.HostingEnvironment.RegisterVirtualPathProvider(new Controllers.StringPathProvider());
Calling the code
string Template = "Hello, #Model.Name";
Models.User user = new Models.User() { Name = "Billy Boy" };
RazorViewEngineRender view = new RazorViewEngineRender(Template);
string Results = view.Render(user); //pass in your model
Notes
This only works with typed Models. I attempted to pass in a new { Name = "Billy Boy" } and it's throwing errors. I'm not sure why and didn't really look too deeply into it.
This was fun, thanks for asking this question.

Razor was designed with standalone operation in mind. There isn't much documentation about that mode yet (since it's all still under development) but have a look at this blog post by Andrew Nurse: http://vibrantcode.com/blog/2010/7/22/using-the-razor-parser-outside-of-aspnet.html

Can I specify a custom location to "search for views" in ASP.NET MVC?

I have the following layout for my mvc project:
/Controllers
/Demo
/Demo/DemoArea1Controller
/Demo/DemoArea2Controller
etc...
/Views
/Demo
/Demo/DemoArea1/Index.aspx
/Demo/DemoArea2/Index.aspx
However, when I have this for DemoArea1Controller:
public class DemoArea1Controller : Controller
{
public ActionResult Index()
{
return View();
}
}
I get the "The view 'index' or its master could not be found" error, with the usual search locations.
How can I specify that controllers in the "Demo" namespace search in the "Demo" view subfolder?

You can easily extend the WebFormViewEngine to specify all the locations you want to look in:
public class CustomViewEngine : WebFormViewEngine
{
public CustomViewEngine()
{
var viewLocations = new[] {
"~/Views/{1}/{0}.aspx",
"~/Views/{1}/{0}.ascx",
"~/Views/Shared/{0}.aspx",
"~/Views/Shared/{0}.ascx",
"~/AnotherPath/Views/{0}.ascx"
// etc
};
this.PartialViewLocationFormats = viewLocations;
this.ViewLocationFormats = viewLocations;
}
}
Make sure you remember to register the view engine by modifying the Application_Start method in your Global.asax.cs
protected void Application_Start()
{
ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(new CustomViewEngine());
}

Now in MVC 6 you can implement IViewLocationExpander interface without messing around with view engines:
public class MyViewLocationExpander : IViewLocationExpander
{
public void PopulateValues(ViewLocationExpanderContext context) {}
public IEnumerable<string> ExpandViewLocations(ViewLocationExpanderContext context, IEnumerable<string> viewLocations)
{
return new[]
{
"/AnotherPath/Views/{1}/{0}.cshtml",
"/AnotherPath/Views/Shared/{0}.cshtml"
}; // add `.Union(viewLocations)` to add default locations
}
}
where {0} is target view name, {1} - controller name and {2} - area name.
You can return your own list of locations, merge it with default viewLocations (.Union(viewLocations)) or just change them (viewLocations.Select(path => "/AnotherPath" + path)).
To register your custom view location expander in MVC, add next lines to ConfigureServices method in Startup.cs file:
public void ConfigureServices(IServiceCollection services)
{
services.Configure<RazorViewEngineOptions>(options =>
{
options.ViewLocationExpanders.Add(new MyViewLocationExpander());
});
}

There's actually a lot easier method than hardcoding the paths into your constructor. Below is an example of extending the Razor engine to add new paths. One thing I'm not entirely sure about is whether the paths you add here will be cached:
public class ExtendedRazorViewEngine : RazorViewEngine
{
public void AddViewLocationFormat(string paths)
{
List<string> existingPaths = new List<string>(ViewLocationFormats);
existingPaths.Add(paths);
ViewLocationFormats = existingPaths.ToArray();
}
public void AddPartialViewLocationFormat(string paths)
{
List<string> existingPaths = new List<string>(PartialViewLocationFormats);
existingPaths.Add(paths);
PartialViewLocationFormats = existingPaths.ToArray();
}
}
And your Global.asax.cs
protected void Application_Start()
{
ViewEngines.Engines.Clear();
ExtendedRazorViewEngine engine = new ExtendedRazorViewEngine();
engine.AddViewLocationFormat("~/MyThemes/{1}/{0}.cshtml");
engine.AddViewLocationFormat("~/MyThemes/{1}/{0}.vbhtml");
// Add a shared location too, as the lines above are controller specific
engine.AddPartialViewLocationFormat("~/MyThemes/{0}.cshtml");
engine.AddPartialViewLocationFormat("~/MyThemes/{0}.vbhtml");
ViewEngines.Engines.Add(engine);
AreaRegistration.RegisterAllAreas();
RegisterRoutes(RouteTable.Routes);
}
One thing to note: your custom location will need the ViewStart.cshtml file in its root.

If you want just add new paths, you can add to the default view engines and spare some lines of code:
ViewEngines.Engines.Clear();
var razorEngine = new RazorViewEngine();
razorEngine.MasterLocationFormats = razorEngine.MasterLocationFormats
.Concat(new[] {
"~/custom/path/{0}.cshtml"
}).ToArray();
razorEngine.PartialViewLocationFormats = razorEngine.PartialViewLocationFormats
.Concat(new[] {
"~/custom/path/{1}/{0}.cshtml", // {1} = controller name
"~/custom/path/Shared/{0}.cshtml"
}).ToArray();
ViewEngines.Engines.Add(razorEngine);
The same applies to WebFormEngine

Instead of subclassing the RazorViewEngine, or replacing it outright, you can just alter existing RazorViewEngine's PartialViewLocationFormats property. This code goes in Application_Start:
System.Web.Mvc.RazorViewEngine rve = (RazorViewEngine)ViewEngines.Engines
.Where(e=>e.GetType()==typeof(RazorViewEngine))
.FirstOrDefault();
string[] additionalPartialViewLocations = new[] {
"~/Views/[YourCustomPathHere]"
};
if(rve!=null)
{
rve.PartialViewLocationFormats = rve.PartialViewLocationFormats
.Union( additionalPartialViewLocations )
.ToArray();
}

Last I checked, this requires you to build your own ViewEngine. I don't know if they made it easier in RC1 though.
The basic approach I used before the first RC was, in my own ViewEngine, to split the namespace of the controller and look for folders which matched the parts.
EDIT:
Went back and found the code. Here's the general idea.
public override ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName)
{
string ns = controllerContext.Controller.GetType().Namespace;
string controller = controllerContext.Controller.GetType().Name.Replace("Controller", "");
//try to find the view
string rel = "~/Views/" +
(
ns == baseControllerNamespace ? "" :
ns.Substring(baseControllerNamespace.Length + 1).Replace(".", "/") + "/"
)
+ controller;
string[] pathsToSearch = new string[]{
rel+"/"+viewName+".aspx",
rel+"/"+viewName+".ascx"
};
string viewPath = null;
foreach (var path in pathsToSearch)
{
if (this.VirtualPathProvider.FileExists(path))
{
viewPath = path;
break;
}
}
if (viewPath != null)
{
string masterPath = null;
//try find the master
if (!string.IsNullOrEmpty(masterName))
{
string[] masterPathsToSearch = new string[]{
rel+"/"+masterName+".master",
"~/Views/"+ controller +"/"+ masterName+".master",
"~/Views/Shared/"+ masterName+".master"
};
foreach (var path in masterPathsToSearch)
{
if (this.VirtualPathProvider.FileExists(path))
{
masterPath = path;
break;
}
}
}
if (string.IsNullOrEmpty(masterName) || masterPath != null)
{
return new ViewEngineResult(
this.CreateView(controllerContext, viewPath, masterPath), this);
}
}
//try default implementation
var result = base.FindView(controllerContext, viewName, masterName);
if (result.View == null)
{
//add the location searched
return new ViewEngineResult(pathsToSearch);
}
return result;
}

Try something like this:
private static void RegisterViewEngines(ICollection<IViewEngine> engines)
{
engines.Add(new WebFormViewEngine
{
MasterLocationFormats = new[] {"~/App/Views/Admin/{0}.master"},
PartialViewLocationFormats = new[] {"~/App/Views/Admin//{1}/{0}.ascx"},
ViewLocationFormats = new[] {"~/App/Views/Admin//{1}/{0}.aspx"}
});
}
protected void Application_Start()
{
RegisterViewEngines(ViewEngines.Engines);
}

Note: for ASP.NET MVC 2 they have additional location paths you will need to set for views in 'Areas'.
AreaViewLocationFormats
AreaPartialViewLocationFormats
AreaMasterLocationFormats
Creating a view engine for an Area is described on Phil's blog.
Note: This is for preview release 1 so is subject to change.

Most of the answers here, clear the existing locations by calling ViewEngines.Engines.Clear() and then add them back in again... there is no need to do this.
We can simply add the new locations to the existing ones, as shown below:
// note that the base class is RazorViewEngine, NOT WebFormViewEngine
public class ExpandedViewEngine : RazorViewEngine
{
public ExpandedViewEngine()
{
var customViewSubfolders = new[]
{
// {1} is conroller name, {0} is action name
"~/Areas/AreaName/Views/Subfolder1/{1}/{0}.cshtml",
"~/Areas/AreaName/Views/Subfolder1/Shared/{0}.cshtml"
};
var customPartialViewSubfolders = new[]
{
"~/Areas/MyAreaName/Views/Subfolder1/{1}/Partials/{0}.cshtml",
"~/Areas/MyAreaName/Views/Subfolder1/Shared/Partials/{0}.cshtml"
};
ViewLocationFormats = ViewLocationFormats.Union(customViewSubfolders).ToArray();
PartialViewLocationFormats = PartialViewLocationFormats.Union(customPartialViewSubfolders).ToArray();
// use the following if you want to extend the master locations
// MasterLocationFormats = MasterLocationFormats.Union(new[] { "new master location" }).ToArray();
}
}
Now you can configure your project to use the above RazorViewEngine in Global.asax:
protected void Application_Start()
{
ViewEngines.Engines.Add(new ExpandedViewEngine());
// more configurations
}
See this tutoral for more info.

I did it this way in MVC 5. I didn't want to clear the default locations.
Helper Class:
namespace ConKit.Helpers
{
public static class AppStartHelper
{
public static void AddConKitViewLocations()
{
// get engine
RazorViewEngine engine = ViewEngines.Engines.OfType<RazorViewEngine>().FirstOrDefault();
if (engine == null)
{
return;
}
// extend view locations
engine.ViewLocationFormats =
engine.ViewLocationFormats.Concat(new string[] {
"~/Views/ConKit/{1}/{0}.cshtml",
"~/Views/ConKit/{0}.cshtml"
}).ToArray();
// extend partial view locations
engine.PartialViewLocationFormats =
engine.PartialViewLocationFormats.Concat(new string[] {
"~/Views/ConKit/{0}.cshtml"
}).ToArray();
}
}
}
And then in Application_Start:
// Add ConKit View locations
ConKit.Helpers.AppStartHelper.AddConKitViewLocations();