How to invalidate Web API cache from another Controller(ASP.NET Web API CacheOutput Library)

I have used ASP.NET Web API CacheOutput Library for my asp.net project for web API and it working fine, but have another controller from where I have a POST method and I would like to invalidate my cache from that controller.

[AutoInvalidateCacheOutput]
public class EmployeeApiController : ApiController
{ 
    [CacheOutput(ClientTimeSpan = 100, ServerTimeSpan = 100)]
    public IEnumerable<DropDown> GetData()
    {
        //Code here
    }
}


public class EmployeesController : BaseController
{
    [HttpPost]
    public ActionResult CreateEmployee (EmployeeEntity empInfo)
    {
        //Code Here
    }
}

I would like to invalidate Employees Cache when there is add\update in employee controller.

It is little tricky, but you can get it in this way:

1. On your WebApiConfig:

// Registering the IApiOutputCache.    
var cacheConfig = config.CacheOutputConfiguration();
cacheConfig.RegisterCacheOutputProvider(() => new MemoryCacheDefault());

We will need of it to get the IApiOutputCache from GlobalConfiguration.Configuration.Properties, if we let the default properties' setup happen the property with the IApiOutputCache won't exists on MVC BaseController request.

2. Create a WebApiCacheHelper class:

using System;
using System.Linq.Expressions;
using System.Web.Http;
using WebApi.OutputCache.Core.Cache;
using WebApi.OutputCache.V2;

namespace MideaCarrier.Bss.WebApi.Controllers
{
    public static class WebApiCacheHelper
    {
        public static void InvalidateCache<T, U>(Expression<Func<T, U>> expression)
        {
            var config = GlobalConfiguration.Configuration;

            // Gets the cache key.
            var outputConfig = config.CacheOutputConfiguration();
            var cacheKey = outputConfig.MakeBaseCachekey(expression);

            // Remove from cache.
            var cache = (config.Properties[typeof(IApiOutputCache)] as Func<IApiOutputCache>)();
            cache.RemoveStartsWith(cacheKey);
        }
    }
}

3. Then, call it from your EmployeesController.CreateEmployee action:

public class EmployeesController : BaseController
{
    [HttpPost]
    public ActionResult CreateEmployee (EmployeeEntity empInfo)
    {
        // your action code Here.
        WebApiCacheHelper.InvalidateCache((EmployeeApiController t) => t.GetData());
    }
}