bradwilson · January 23, 2014 20:53 · Jan 23, 2014
diff --git a/Cacheability.cs b/Cacheability.cs
@@ -0,0 +1,6 @@
+public enum Cacheability
+{
+    NoCache,
+    Private,
+    Public,
+}
diff --git a/CachedResult.cs b/CachedResult.cs
@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Web.Http;
+
+public class CachedResult<T> : IHttpActionResult
+    where T : IHttpActionResult
+{
+    public CachedResult(
+        T innerResult,
+        Cacheability cacheability,
+        string eTag,
+        DateTimeOffset? expires,
+        DateTimeOffset? lastModified,
+        TimeSpan? maxAge,
+        bool? noStore)
+    {
+        Cacheability = cacheability;
+        ETag = eTag;
+        Expires = expires;
+        InnerResult = innerResult;
+        LastModified = lastModified;
+        MaxAge = maxAge;
+        NoStore = noStore;
+    }
+
+    public Cacheability Cacheability { get; private set; }
+    public string ETag { get; private set; }
+    public DateTimeOffset? Expires { get; private set; }
+    public T InnerResult { get; private set; }
+    public DateTimeOffset? LastModified { get; private set; }
+    public TimeSpan? MaxAge { get; private set; }
+    public bool? NoStore { get; private set; }
+
+    public async Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
+    {
+        var response = await InnerResult.ExecuteAsync(cancellationToken);
+        if (!response.Headers.Date.HasValue)
+            response.Headers.Date = DateTimeOffset.UtcNow;
+
+        response.Headers.CacheControl = new CacheControlHeaderValue
+        {
+            NoCache = Cacheability == Cacheability.NoCache,
+            Private = Cacheability == Cacheability.Private,
+            Public = Cacheability == Cacheability.Public
+        };
+
+        if (response.Headers.CacheControl.NoCache)
+        {
+            response.Headers.Pragma.TryParseAdd("no-cache");
+            response.Content.Headers.Expires = response.Headers.Date;
+            return response;  // None of the other headers are valid
+        }
+
+        response.Content.Headers.Expires = Expires;
+        response.Content.Headers.LastModified = LastModified;
+        response.Headers.CacheControl.MaxAge = MaxAge;
+
+        if (!String.IsNullOrWhiteSpace(ETag))
+            response.Headers.ETag = new EntityTagHeaderValue(String.Format("\"{0}\"", ETag));
+
+        if (NoStore.HasValue)
+            response.Headers.CacheControl.NoStore = NoStore.Value;
+
+        return response;
+    }
+}
diff --git a/HttpActionResultExtensions.cs b/HttpActionResultExtensions.cs
@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Web.Http;
+
+public static class HttpActionResultExtensions
+{
+    public static CachedResult<T> Cached<T>(
+        this T actionResult,
+        Cacheability cacheability = Cacheability.Private,
+        string eTag = null,
+        DateTimeOffset? expires = null,
+        DateTimeOffset? lastModified = null,
+        TimeSpan? maxAge = null,
+        bool? noStore = null) where T : IHttpActionResult
+    {
+        return new CachedResult<T>(actionResult, cacheability, eTag, expires, lastModified, maxAge, noStore);
+    }
+}
diff --git a/SampleController.cs b/SampleController.cs
@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Web.Http;
+
+public SampleController : ApiController
+{
+    public IHttpActionResult GetExample(string name)
+    {
+        return Ok("Hello, " + name).Cached(Cacheability.Public, maxAge: TimeSpan.FromMinutes(15));
+    }
+}