Use CacheProfile attribute with output caching in asp.net mvc November 22, 2009

I’ve recently been setting up some caching on a new Asp.Net MVC site by using the OutputCache attribute on my controllers:

//cache this for an hour
 [OutputCache(Duration=60 * 60, VaryByParam="")]

This works really well except that it means hard codeding the cache time into my app so if I want to change it I need to recompile and deploy my code which is obviously far from ideal. So I changed my code to load the value from the web.config and ran into this error:

‘An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type’

Not very helpful.

But fortunately there is a better way of doing all this using cache profiles, I just set up a cache profile in my web.config:

<system.web>
<caching>
<outputCacheSettings>
<outputCacheProfiles>
<add name="HomePage" duration="3600" varyByParam="None" location="ServerAndClient"/>
</outputCacheProfiles>
</outputCacheSettings>

</caching>

</system.web>

And then reference this in my attribute:

 [OutputCache( CacheProfile="HomePage")]

And bingo, we’re sucking diesel as a friend of mine says!

Create an Asp.Net MVC HtmlHelper for use in unit tests November 17, 2009

Here’s a utility factory class to create an HtmlHelper instance so that you can unit test extension methods written on it. It will take a controller and a model for methods which rely on those. I adapted it from this post, and changed it to work with Asp.Net version 1.0 and to accept a model.

class HtmlHelperFactory
 {
 public static HtmlHelper CreateInstance(RouteData route, Controller controller)
 {
 return CreateInstance(route, controller, null);
 }
 public static HtmlHelper CreateInstance(RouteData route, Controller controller, object model)
 {
 HttpContextBase httpContext = new HttpContextDummy();

 var cc = new ControllerContext(httpContext, route, controller);
 var vd = new ViewDataDictionary(model);
 ViewContext vc = new ViewContext(cc, new ViewDummy(), vd, new TempDataDictionary());
 return new HtmlHelper(vc, new ViewDataContainerDummy(vd), new RouteCollection());
 }

 // Dummy classes needed to be able to create HtmlHelper

 private class HttpRequestDummy : HttpRequestBase
 {
 public override string ApplicationPath
 {
 get { return ""; }
 }

 public override string AppRelativeCurrentExecutionFilePath
 {
 // Any shorter string here gives exception:
 // index larger than length of string
 get { return "~/"; }
 }

 public override string PathInfo
 {
 get { return ""; }
 }
 }

 private class HttpResponseDummy : HttpResponseBase
 {
 public override string ApplyAppPathModifier(string virtualPath)
 {
 return virtualPath;
 }
 }

 private class HttpContextDummy : HttpContextBase
 {
 public override HttpRequestBase Request
 {
 get { return new HttpRequestDummy(); }
 }

 public override HttpResponseBase Response
 {
 get { return new HttpResponseDummy(); }
 }
 }

 private class ViewDummy : IView
 {
 public void Render(ViewContext viewContext, System.IO.TextWriter writer)
 {
 throw new NotImplementedException();
 }
 }

 private class ViewDataContainerDummy : IViewDataContainer
 {
 public ViewDataContainerDummy()
 {
 }

 public ViewDataContainerDummy(ViewDataDictionary dataDictionary)
 {
 _data = dataDictionary;
 }

 private ViewDataDictionary _data;
 public ViewDataDictionary ViewData
 {
 get { return _data; }
 set { _data = value; }
 }
 }
 }

 

Access RouteData for the current Route from a library class in asp.net mvc October 7, 2009

Sometimes it’s useful to be able to access the current RouteData from outside a controller, for instance in a library class. In webforms you could always do

HttpContext.Current

but in Asp.Net MVC it’s a bit less obvious how you get access to this data.

I’ve found the following code works:

RouteTable.Routes.GetRouteData(new HttpContextWrapper(HttpContext.Current));

Whether there is an easier way or not I don’t know, but this will do me for now…

Enumeration model binder for asp.net mvc August 8, 2009

We were recently working on an asp.net MVC app and I noticed that in a lot of places actions were taking strings as parameters and then converting them to enum values with the action. The reason for doing this rather than just typing the parameter as the enum type was because they were optional and so when the value didn’t exist an error was thrown:

screenshot of error page

Because enums are not nullable types they can’t be used as optional parameters.

What was needed then was a way to provide a default parameter for when the parameter didn’t exist in the url. To do this I wrote a custom model binder and it solved the problem pretty well.

Here is the code for the binder

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace EnumTest.Helpers
{
public class EnumBinder<T> : IModelBinder
{
private T DefaultValue { get; set; }
public EnumBinder(T defaultValue)
{
DefaultValue = defaultValue;
}

#region IModelBinder Members
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
return bindingContext.ValueProvider[bindingContext.ModelName] == null
? DefaultValue
: GetEnumValue(DefaultValue, bindingContext.ValueProvider[bindingContext.ModelName].AttemptedValue);
}

#endregion

public static T GetEnumValue<T>(T defaultValue, string value)
{
T enumType = defaultValue;

if ((!String.IsNullOrEmpty(value)) && (Contains(typeof(T), value)))
enumType = (T)Enum.Parse(typeof(T), value, true);

return enumType;
}
public static bool Contains(Type enumType, string value)
{
return Enum.GetNames(enumType).Contains(value, StringComparer.OrdinalIgnoreCase);
}
}
}

And to use it in your project you just register it in your Global.asax, specifying the type of your enum and the default value you want when there is no value available in the input.

protected void Application_Start()
        {
            RegisterRoutes(RouteTable.Routes);
            ModelBinders.Binders.Add(typeof(TestEnum), new EnumBinder<TestEnum>(TestEnum.rupert));
        }