I was working on a small MVC project where we were dealing with Inherited controllers (SomeController was inherited by SomeMoreSpecificController) and we decided that it’d be nice to have a similar hierarchy of sharing and inheritance at the View level.
Unfortunately, out of the box, ASP.net MVC looks in two default locations for your views and partials by convention. The first is /Views/ControllerName/ViewName.aspx, the second is /Views/Shared/ViewName.aspx. We wanted to allow SomeController to have it’s own set of more generic views, that could later be overridden in special cases by the views provided by SomeMoreSpecificController.
In order to do this in ASP.net MVC, you need to override the default view engine to change the location that the runtime looks for your views.
“Here’s one I made earlier”.
Using this ViewEngine, if you call an action method on SomeMoreSpecificController it’ll first check /Views/SomeMoreSpecificController/…, then /Views/SomeController/… (the base class), then finally /Views/Shared, allowing you a little more control over the organisation of your views.
using System.Collections.Generic;
using System.Web.Mvc;
using System;
using System.Globalization;
using System.Linq;
namespace MyMvc.Mvc
{
public class InheranceViewEngine : WebFormViewEngine
{
private const string CacheKeyFormat = ":ViewCacheEntry:{0}:{1}:{2}:{3}:";
private const string CacheKeyPrefixMaster = "Master";
private const string CacheKeyPrefixView = "View";
private static readonly List<string> EmptyLocations= new List<string>();
public InheranceViewEngine()
{
ViewLocationFormats = new[]
{
"~/Views/{1}/{0}.aspx", "~/Views/{1}/{0}.ascx", "~/Views/Shared/{0}.aspx",
"~/Views/Shared/{0}.ascx"
};
}
public override ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
if (String.IsNullOrEmpty(viewName))
{
throw new ArgumentException("viewName");
}
List<string> viewLocationsSearched;
List<string> masterLocationsSearched;
string controllerName = controllerContext.RouteData.GetRequiredString("controller");
string viewPath = GetPath(controllerContext, ViewLocationFormats, viewName, controllerName, CacheKeyPrefixView, useCache, out viewLocationsSearched);
string masterPath = GetPath(controllerContext, MasterLocationFormats, masterName, controllerName, CacheKeyPrefixMaster, useCache, out masterLocationsSearched);
if (String.IsNullOrEmpty(viewPath) || (String.IsNullOrEmpty(masterPath) && !String.IsNullOrEmpty(masterName)))
{
return new ViewEngineResult(viewLocationsSearched.Union(masterLocationsSearched));
}
return new ViewEngineResult(CreateView(controllerContext, viewPath, masterPath), this);
}
public override ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache)
{
List<string> strArray;
if (controllerContext == null) { throw new ArgumentNullException("controllerContext"); }
if (string.IsNullOrEmpty(partialViewName)) { throw new ArgumentException("Partial View Name is null or empty.", "partialViewName"); }
string requiredString = controllerContext.RouteData.GetRequiredString("controller");
string str2 = GetPath(controllerContext, PartialViewLocationFormats, partialViewName, requiredString, "Partial", useCache, out strArray);
if (string.IsNullOrEmpty(str2))
{
return new ViewEngineResult(strArray);
}
return new ViewEngineResult(CreatePartialView(controllerContext, str2), this);
}
private string GetPath(ControllerContext controllerContext, string[] locations, string name, string controllerName, string cacheKeyPrefix, bool useCache, out List<string> searchedLocations)
{
searchedLocations = EmptyLocations;
if (String.IsNullOrEmpty(name))
{
return String.Empty;
}
if (locations == null || locations.Length == 0)
{
throw new InvalidOperationException();
}
bool nameRepresentsPath = IsSpecificPath(name);
string cacheKey = CreateCacheKey(cacheKeyPrefix, name, (nameRepresentsPath) ? String.Empty : controllerName);
if (useCache)
{
string result = ViewLocationCache.GetViewLocation(controllerContext.HttpContext, cacheKey);
if (result != null)
{
return result;
}
}
if (nameRepresentsPath)
{
return GetPathFromSpecificName(controllerContext, name, cacheKey, ref searchedLocations);
}
return GetPathFromGeneralName(controllerContext, locations, name, controllerName, cacheKey, ref searchedLocations);
}
private string GetPathFromGeneralName(ControllerContext controllerContext, string[] locations, string name, string controllerName, string cacheKey, ref List<string> searchedLocations)
{
string result = String.Empty;
searchedLocations = new List<string>();
for (int i = 0; i < locations.Length; i++)
{
string virtualPath = String.Format(CultureInfo.InvariantCulture, locations[i], name, controllerName);
if (FileExists(controllerContext, virtualPath))
{
searchedLocations = EmptyLocations;
result = virtualPath;
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
return result;
}
searchedLocations.Add(virtualPath);
}
return GetPathFromGeneralNameOfBaseTypes(controllerContext.Controller.GetType(), locations, name, controllerContext, cacheKey, result, ref searchedLocations);
}
private string GetPathFromGeneralNameOfBaseTypes(Type descendantType, string[] locations, string name, ControllerContext controllerContext, string cacheKey, string result, ref List<string> searchedLocations)
{
Type baseControllerType = descendantType;
if (baseControllerType == null
|| !baseControllerType.Name.Contains("Controller")
|| baseControllerType.Name == "Controller")
{
return result;
}
for (int i = 0;i < locations.Length;i++)
{
string baseControllerName = baseControllerType.Name.Replace("Controller", "");
string virtualPath = String.Format(CultureInfo.InvariantCulture, locations[i], name, baseControllerName);
if (!string.IsNullOrEmpty(virtualPath) &&
FileExists(controllerContext, virtualPath))
{
searchedLocations = EmptyLocations;
result = virtualPath;
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
return result;
}
searchedLocations.Add(virtualPath);
}
return GetPathFromGeneralNameOfBaseTypes(baseControllerType.BaseType, locations, name, controllerContext,
cacheKey, result, ref searchedLocations);
}
private string CreateCacheKey(string prefix, string name, string controllerName)
{
return String.Format(CultureInfo.InvariantCulture, CacheKeyFormat,
GetType().AssemblyQualifiedName, prefix, name, controllerName);
}
private string GetPathFromSpecificName(ControllerContext controllerContext, string name, string cacheKey, ref List<string> searchedLocations)
{
string result = name;
if (!FileExists(controllerContext, name))
{
result = String.Empty;
searchedLocations = new List<string>{ name };
}
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
return result;
}
private static bool IsSpecificPath(string name)
{
char c = name[0];
return (c == ‘~’ || c == ‘/’);
}
}
}
