Memory Cache in web api

Question

I was looking for Caching in my web api where i can use output of one api method(that changes once in 12hrs) for subsequesnt calls and then i found this solution on SO,but i am having a difficulty in understanding and using the below code

private IEnumerable<TEntity> GetFromCache<TEntity>(string key, Func<IEnumerable<TEntity>> valueFactory) where TEntity : class 
{
    ObjectCache cache = MemoryCache.Default;
    var newValue = new Lazy<IEnumerable<TEntity>>(valueFactory);            
    CacheItemPolicy policy = new CacheItemPolicy { AbsoluteExpiration = DateTimeOffset.Now.AddMinutes(30) };
    //The line below returns existing item or adds the new value if it doesn't exist
    var value = cache.AddOrGetExisting(key, newValue, policy) as Lazy<IEnumerable<TEntity>>;
    return (value ?? newValue).Value; // Lazy<T> handles the locking itself
}

I am not sure how to call and use this method in below context? I have a method Get

  public IEnumerable<Employee> Get()
    {
        return repository.GetEmployees().OrderBy(c => c.EmpId);
    }

and i want to cache the output of Get and use it in my other methods GetEmployeeById() or Search()

        public Movie GetEmployeeById(int EmpId)
        {
           //Search Employee in Cached Get
        }

        public IEnumerable<Employee> GetEmployeeBySearchString(string searchstr)
        {
          //Search in Cached Get
        }

marc_s · Accepted Answer · 2024-07-16 16:13:22Z

11

I updated your method to return classes instead of IEnumerable:

private TEntity GetFromCache<TEntity>(string key, Func<TEntity> valueFactory) where TEntity : class 
{
    ObjectCache cache = MemoryCache.Default;
    // the lazy class provides lazy initializtion which will evaluate the valueFactory expression only if the item does not exist in cache
    var newValue = new Lazy<TEntity>(valueFactory);            
    CacheItemPolicy policy = new CacheItemPolicy 
                                 {
                                     AbsoluteExpiration = DateTimeOffset.Now.AddMinutes(30) 
                                 };

    // The line below returns existing item or adds the new value if it doesn't exist
    var value = cache.AddOrGetExisting(key, newValue, policy) as Lazy<TEntity>;

    return (value ?? newValue).Value; // Lazy<T> handles the locking itself
}

Then you can use this method like this:

public Movie GetMovieById(int movieId)
{
    var cacheKey = "movie" + movieId;

    var movie = GetFromCache<Movie>(cacheKey, () => {       
        // load movie from DB
        return context.Movies.First(x => x.Id == movieId); 
    });

    return movie;
}

and to search movies

[ActionName("Search")]
public IEnumerable<Movie> GetMovieBySearchParameter(string searchstr)
{
     var cacheKey = "movies" + searchstr;
     var movies = GetFromCache<IEnumerable<Movie>>(cacheKey, () => {               
          return repository.GetMovies().OrderBy(c => c.MovieId).ToList(); 
     });

     return movies;
}

edited Jul 16, 2024 at 16:13

marc_s

760k186 gold badges1.4k silver badges1.5k bronze badges

answered Oct 27, 2014 at 8:22

Marian Ban

8,1881 gold badge35 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Marian Ban Over a year ago

@little it is done inside of the GetFromCache method

Marian Ban Over a year ago

@little you should call your repository inside of the valueFactory function (it will be executed only if the object is not in the cache). Look at my answer i'm not calling a repository but directly the context so just replace the context with repository.

Marian Ban Over a year ago

@little i updated the GetMovieBySearchParameter method in my example and now it is using a repository.

Marian Ban Over a year ago

@F11, hi, what do you want to ask?

Marian Ban Over a year ago

@F11 yes, send me a link to chat.

Collectives™ on Stack Overflow

Memory Cache in web api

1 Answer 1

5 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related