Setting HTTP cache control headers in Web API

Question

As suggested in the comments, you can create an ActionFilterAttribute. Here's a simple one that only handles the MaxAge property:

public class CacheControlAttribute : System.Web.Http.Filters.ActionFilterAttribute
{
    public int MaxAge { get; set; }

    public CacheControlAttribute()
    {
        MaxAge = 3600;
    }

    public override void OnActionExecuted(HttpActionExecutedContext context)
    {
        if (context.Response != null)
            context.Response.Headers.CacheControl = new CacheControlHeaderValue()
            {
                Public = true,
                MaxAge = TimeSpan.FromSeconds(MaxAge)
            };

        base.OnActionExecuted(context);
    }
}

Then you can apply it to your methods:

 [CacheControl(MaxAge = 60)]
 public string GetFoo(int id)
 {
    // ...
 }

The cache control header can be set like this.

public HttpResponseMessage GetFoo(int id)
{
    var foo = _FooRepository.GetFoo(id);
    var response = Request.CreateResponse(HttpStatusCode.OK, foo);
    response.Headers.CacheControl = new CacheControlHeaderValue()
        {
            Public = true,
            MaxAge = new TimeSpan(1, 0, 0, 0)
        };
    return response;
}

In case anyone lands here looking for an answer specifically to ASP.NET Core, you can now do what @Jacob suggested without writing your own filter. Core already includes this:

[ResponseCache(VaryByHeader = "User-Agent", Duration = 1800)]
public async Task<JsonResult> GetData()
{
}

https://docs.microsoft.com/en-us/aspnet/core/performance/caching/response

Like this answer suggesting filters, consider the "extended" version -- http://www.strathweb.com/2012/05/output-caching-in-asp-net-web-api/

It used to be available as a NuGet package Strathweb.CacheOutput.WebApi2, but doesn't seem to be hosted anymore, and is instead on GitHub -- https://github.com/filipw/AspNetWebApi-OutputCache