How to cache data in a MVC application

I have read lots of information about page caching and partial page caching in a MVC application. However, I would like to know how you would cache data.

In my scenario I will be using LINQ to Entities (entity framework). On the first call to GetNames (or whatever the method is) I want to grab the data from the database. I want to save the results in cache and on the second call to use the cached version if it exists.

Can anyone show an example of how this would work, where this should be implemented (model?) and if it would work.

I have seen this done in traditional ASP.NET apps , typically for very static data.

Here's a nice and simple cache helper class/service I use:

using System.Runtime.Caching;  

public class InMemoryCache: ICacheService
{
    public T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class
    {
        T item = MemoryCache.Default.Get(cacheKey) as T;
        if (item == null)
        {
            item = getItemCallback();
            MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(10));
        }
        return item;
    }
}

interface ICacheService
{
    T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class;
}

###Usage:

cacheProvider.GetOrSet("cache key", (delegate method if cache is empty));

Cache provider will check if there's anything by the name of "cache id" in the cache, and if there's not, it will call a delegate method to fetch data and store it in cache.

###Example:

var products=cacheService.GetOrSet("catalog.products", ()=>productRepository.GetAll())

Reference the System.Web dll in your model and use System.Web.Caching.Cache

    public string[] GetNames()
    {
      string[] names = Cache["names"] as string[];
      if(names == null) //not in cache
      {
        names = DB.GetNames();
        Cache["names"] = names;
      }
      return names;
    }

A bit simplified but I guess that would work. This is not MVC specific and I have always used this method for caching data.

I'm referring to TT's post and suggest the following approach:

Reference the System.Web dll in your model and use System.Web.Caching.Cache

public string[] GetNames()
{ 
    var noms = Cache["names"];
    if(noms == null) 
    {    
        noms = DB.GetNames();
        Cache["names"] = noms; 
    }

    return ((string[])noms);
}

You should not return a value re-read from the cache, since you'll never know if at that specific moment it is still in the cache. Even if you inserted it in the statement before, it might already be gone or has never been added to the cache - you just don't know.

So you add the data read from the database and return it directly, not re-reading from the cache.

For .NET 4.5+ framework

add reference: System.Runtime.Caching

add using statement: using System.Runtime.Caching;

public string[] GetNames()
{ 
    var noms = System.Runtime.Caching.MemoryCache.Default["names"];
    if(noms == null) 
    {    
        noms = DB.GetNames();
        System.Runtime.Caching.MemoryCache.Default["names"] = noms; 
    }

    return ((string[])noms);
}

> In the .NET Framework 3.5 and earlier versions, ASP.NET provided an in-memory cache implementation in the System.Web.Caching namespace. In previous versions of the .NET Framework, caching was available only in the System.Web namespace and therefore required a dependency on ASP.NET classes. In the .NET Framework 4, the System.Runtime.Caching namespace contains APIs that are designed for both Web and non-Web applications.

More info:

• https://msdn.microsoft.com/en-us/library/dd997357(v=vs.110).aspx

• https://docs.microsoft.com/en-us/dotnet/framework/performance/caching-in-net-framework-applications

Steve Smith did two great blog posts which demonstrate how to use his CachedRepository pattern in ASP.NET MVC. It uses the repository pattern effectively and allows you to get caching without having to change your existing code.

http://ardalis.com/Introducing-the-CachedRepository-Pattern

http://ardalis.com/building-a-cachedrepository-via-strategy-pattern

In these two posts he shows you how to set up this pattern and also explains why it is useful. By using this pattern you get caching without your existing code seeing any of the caching logic. Essentially you use the cached repository as if it were any other repository.

I have used it in this way and it works for me. https://msdn.microsoft.com/en-us/library/system.web.caching.cache.add(v=vs.110).aspx parameters info for system.web.caching.cache.add.

public string GetInfo()
{
     string name = string.Empty;
     if(System.Web.HttpContext.Current.Cache["KeyName"] == null)
     {
         name = GetNameMethod();
         System.Web.HttpContext.Current.Cache.Add("KeyName", name, null, DateTime.Noew.AddMinutes(5), Cache.NoSlidingExpiration, CacheitemPriority.AboveNormal, null);
     }
     else
     {
         name = System.Web.HttpContext.Current.Cache["KeyName"] as string;
     }

      return name;
         
}

AppFabric Caching is distributed and an in-memory caching technic that stores data in key-value pairs using physical memory across multiple servers. AppFabric provides performance and scalability improvements for .NET Framework applications. Concepts and Architecture

Extending @Hrvoje Hudo's answer...

Code:

using System;
using System.Runtime.Caching;

public class InMemoryCache : ICacheService
{
    public TValue Get<TValue>(string cacheKey, int durationInMinutes, Func<TValue> getItemCallback) where TValue : class
    {
        TValue item = MemoryCache.Default.Get(cacheKey) as TValue;
        if (item == null)
        {
            item = getItemCallback();
            MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(durationInMinutes));
        }
        return item;
    }

    public TValue Get<TValue, TId>(string cacheKeyFormat, TId id, int durationInMinutes, Func<TId, TValue> getItemCallback) where TValue : class
    {
        string cacheKey = string.Format(cacheKeyFormat, id);
        TValue item = MemoryCache.Default.Get(cacheKey) as TValue;
        if (item == null)
        {
            item = getItemCallback(id);
            MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(durationInMinutes));
        }
        return item;
    }
}

interface ICacheService
{
    TValue Get<TValue>(string cacheKey, Func<TValue> getItemCallback) where TValue : class;
    TValue Get<TValue, TId>(string cacheKeyFormat, TId id, Func<TId, TValue> getItemCallback) where TValue : class;
}

Examples

Single item caching (when each item is cached based on its ID because caching the entire catalog for the item type would be too intensive).

Product product = cache.Get("product_{0}", productId, 10, productData.getProductById);

Caching all of something

IEnumerable<Categories> categories = cache.Get("categories", 20, categoryData.getCategories);

Why TId

The second helper is especially nice because most data keys are not composite. Additional methods could be added if you use composite keys often. In this way you avoid doing all sorts of string concatenation or string.Formats to get the key to pass to the cache helper. It also makes passing the data access method easier because you don't have to pass the ID into the wrapper method... the whole thing becomes very terse and consistant for the majority of use cases.

Here's an improvement to Hrvoje Hudo's answer. This implementation has a couple of key improvements:

• Cache keys are created automatically based on the function to update data and the object passed in that specifies dependencies
• Pass in time span for any cache duration
• Uses a lock for thread safety

Note that this has a dependency on Newtonsoft.Json to serialize the dependsOn object, but that can be easily swapped out for any other serialization method.

ICache.cs

public interface ICache
{
    T GetOrSet<T>(Func<T> getItemCallback, object dependsOn, TimeSpan duration) where T : class;
}

InMemoryCache.cs

using System;
using System.Reflection;
using System.Runtime.Caching;
using Newtonsoft.Json;

public class InMemoryCache : ICache
{
    private static readonly object CacheLockObject = new object();

    public T GetOrSet<T>(Func<T> getItemCallback, object dependsOn, TimeSpan duration) where T : class
    {
        string cacheKey = GetCacheKey(getItemCallback, dependsOn);
        T item = MemoryCache.Default.Get(cacheKey) as T;
        if (item == null)
        {
            lock (CacheLockObject)
            {
                item = getItemCallback();
                MemoryCache.Default.Add(cacheKey, item, DateTime.Now.Add(duration));
            }
        }
        return item;
    }

    private string GetCacheKey<T>(Func<T> itemCallback, object dependsOn) where T: class
    {
        var serializedDependants = JsonConvert.SerializeObject(dependsOn);
        var methodType = itemCallback.GetType();
        return methodType.FullName + serializedDependants;
    }
}

Usage:

var order = _cache.GetOrSet(
    () => _session.Set<Order>().SingleOrDefault(o => o.Id == orderId)
    , new { id = orderId }
    , new TimeSpan(0, 10, 0)
);

public sealed class CacheManager
{
	private static volatile CacheManager instance;
	private static object syncRoot = new Object();
	private ObjectCache cache = null;
	private CacheItemPolicy defaultCacheItemPolicy = null;

	private CacheEntryRemovedCallback callback = null;
	private bool allowCache = true;

	private CacheManager()
	{
		cache = MemoryCache.Default;
		callback = new CacheEntryRemovedCallback(this.CachedItemRemovedCallback);

		defaultCacheItemPolicy = new CacheItemPolicy();
		defaultCacheItemPolicy.AbsoluteExpiration = DateTime.Now.AddHours(1.0);
		defaultCacheItemPolicy.RemovedCallback = callback;
		allowCache = StringUtils.Str2Bool(ConfigurationManager.AppSettings["AllowCache"]); ;
	}
	public static CacheManager Instance
	{
		get
		{
			if (instance == null)
			{
				lock (syncRoot)
				{
					if (instance == null)
					{
						instance = new CacheManager();
					}
				}
			}

			return instance;
		}
	}

	public IEnumerable GetCache(String Key)
	{
		if (Key == null || !allowCache)
		{
			return null;
		}

		try
		{
			String Key_ = Key;
            if (cache.Contains(Key_))
			{
                return (IEnumerable)cache.Get(Key_);
			}
			else
			{
				return null;
			}
		}
		catch (Exception)
		{
			return null;
		}
	}

	public void ClearCache(string key)
	{
		AddCache(key, null);
	}

	public bool AddCache(String Key, IEnumerable data, CacheItemPolicy cacheItemPolicy = null)
	{
		if (!allowCache) return true;
		try
		{
			if (Key == null)
			{
				return false;
			}

			if (cacheItemPolicy == null)
			{
				cacheItemPolicy = defaultCacheItemPolicy;
			}

			String Key_ = Key;

            lock (Key_)
			{
                return cache.Add(Key_, data, cacheItemPolicy);
			}
		}
		catch (Exception)
		{
			return false;
		}
	}

	private void CachedItemRemovedCallback(CacheEntryRemovedArguments arguments)
	{
		String strLog = String.Concat("Reason: ", arguments.RemovedReason.ToString(), " | Key-Name: ", arguments.CacheItem.Key, " | Value-Object: ", arguments.CacheItem.Value.ToString());
		LogManager.Instance.Info(strLog);
	}
}

I use two classes. First one the cache core object:

public class Cacher<TValue>
    where TValue : class
{
    #region Properties
    private Func<TValue> _init;
    public string Key { get; private set; }
    public TValue Value
    {
        get
        {
            var item = HttpRuntime.Cache.Get(Key) as TValue;
            if (item == null)
            {
                item = _init();
                HttpContext.Current.Cache.Insert(Key, item);
            }
            return item;
        }
    }
    #endregion

    #region Constructor
    public Cacher(string key, Func<TValue> init)
    {
        Key = key;
        _init = init;
    }
    #endregion

    #region Methods
    public void Refresh()
    {
        HttpRuntime.Cache.Remove(Key);
    }
    #endregion
}

Second one is list of cache objects:

public static class Caches
{
    static Caches()
    {
        Languages = new Cacher<IEnumerable<Language>>("Languages", () =>
                                                          {
                                                              using (var context = new WordsContext())
                                                              {
                                                                  return context.Languages.ToList();
                                                              }
                                                          });
    }
    public static Cacher<IEnumerable<Language>> Languages { get; private set; }
}

I will say implementing Singleton on this persisting data issue can be a solution for this matter in case you find previous solutions much complicated

 public class GPDataDictionary
{
    private Dictionary<string, object> configDictionary = new Dictionary<string, object>();

    /// <summary>
    /// Configuration values dictionary
    /// </summary>
    public Dictionary<string, object> ConfigDictionary
    {
        get { return configDictionary; }
    }

    private static GPDataDictionary instance;
    public static GPDataDictionary Instance
    {
        get
        {
            if (instance == null)
            {
                instance = new GPDataDictionary();
            }
            return instance;
        }
    }

    // private constructor
    private GPDataDictionary() { }

}  // singleton

HttpContext.Current.Cache.Insert("subjectlist", subjectlist);

You can also try and use the caching built into ASP MVC:

Add the following attribute to the controller method you'd like to cache:

[OutputCache(Duration=10)]

In this case the ActionResult of this will be cached for 10 seconds.

More on this here