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

Question

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?

Answer 1

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());
}

Answer 2

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());
    });
}

Answer 3

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.

Answer 4

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

Answer 5

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();
}

Answer 6

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;
}

Answer 7

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);
}

Answer 8

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.