MemoryCache - AddOrGetExisting

A MemoryCache extension method that adds an or get existing.

public static void Main()
{
   var cache2 = new CacheTest();
   var cache3 = new CacheTest();
   var cache4 = new CacheTest();

   System.Runtime.Caching.MemoryCache cache = System.Runtime.Caching.MemoryCache.Default;

	//C# Extension Method: MemoryCache - AddOrGetExisting
   int cache1_1 = cache.AddOrGetExisting("cache1", 1);
   int cache1_2 = cache.AddOrGetExisting("cache1", 2);

   int cache2_1 = cache.AddOrGetExisting("cache2", i => cache2.Increment());
   int cache2_2 = cache.AddOrGetExisting("cache2", i => cache2.Increment());

   int cache3_1 = cache.AddOrGetExisting("cache3", i => cache3.Increment(), new CacheItemPolicy());
   int cache3_2 = cache.AddOrGetExisting("cache3", i => cache3.Increment(), new CacheItemPolicy());

   int cache4_1 = cache.AddOrGetExisting("cache4", i => cache4.Increment(), new DateTimeOffset(new DateTime(2100, 01, 01)));
   int cache4_2 = cache.AddOrGetExisting("cache4", i => cache4.Increment(), new DateTimeOffset(new DateTime(2100, 01, 01)));
	
	Console.WriteLine(cache1_1);
    Console.WriteLine(cache1_2);

    Console.WriteLine(cache2_1);
    Console.WriteLine(cache2_2);

    Console.WriteLine(cache3_1);
    Console.WriteLine(cache3_2);
	
	Console.WriteLine(cache4_1);
    Console.WriteLine(cache4_2);
}

public class CacheTest
{
    public int Cache = 0;

    public int Increment()
    {
        Cache++;
        return Cache;
    }
}

View Source

using System;
#if !NETSTANDARD
using System.Runtime.Caching;
#endif

public static partial class Extensions
{
#if !NETSTANDARD
    /// <summary>A MemoryCache extension method that adds an or get existing.</summary>
    /// <typeparam name="TValue">Type of the value.</typeparam>
    /// <param name="cache">The cache to act on.</param>
    /// <param name="key">The key.</param>
    /// <param name="value">The value.</param>
    /// <returns>A TValue.</returns>
    public static TValue AddOrGetExisting<TValue>(this MemoryCache cache, string key, TValue value)
    {
        object item = cache.AddOrGetExisting(key, value, new CacheItemPolicy()) ?? value;

        return (TValue) item;
    }

    /// <summary>A MemoryCache extension method that adds an or get existing.</summary>
    /// <typeparam name="TValue">Type of the value.</typeparam>
    /// <param name="cache">The cache to act on.</param>
    /// <param name="key">The key.</param>
    /// <param name="valueFactory">The value factory.</param>
    /// <returns>A TValue.</returns>
    public static TValue AddOrGetExisting<TValue>(this MemoryCache cache, string key, Func<string, TValue> valueFactory)
    {
        var lazy = new Lazy<TValue>(() => valueFactory(key));

        Lazy<TValue> item = (Lazy<TValue>) cache.AddOrGetExisting(key, lazy, new CacheItemPolicy()) ?? lazy;

        return item.Value;
    }

    /// <summary>A MemoryCache extension method that adds an or get existing.</summary>
    /// <typeparam name="TValue">Type of the value.</typeparam>
    /// <param name="cache">The cache to act on.</param>
    /// <param name="key">The key.</param>
    /// <param name="valueFactory">The value factory.</param>
    /// <param name="policy">The policy.</param>
    /// <param name="regionName">(Optional) name of the region.</param>
    /// <returns>A TValue.</returns>
    public static TValue AddOrGetExisting<TValue>(this MemoryCache cache, string key, Func<string, TValue> valueFactory, CacheItemPolicy policy, string regionName = null)
    {
        var lazy = new Lazy<TValue>(() => valueFactory(key));

        Lazy<TValue> item = (Lazy<TValue>) cache.AddOrGetExisting(key, lazy, policy, regionName) ?? lazy;

        return item.Value;
    }

    /// <summary>A MemoryCache extension method that adds an or get existing.</summary>
    /// <typeparam name="TValue">Type of the value.</typeparam>
    /// <param name="cache">The cache to act on.</param>
    /// <param name="key">The key.</param>
    /// <param name="valueFactory">The value factory.</param>
    /// <param name="absoluteExpiration">The policy.</param>
    /// <param name="regionName">(Optional) name of the region.</param>
    /// <returns>A TValue.</returns>
    public static TValue AddOrGetExisting<TValue>(this MemoryCache cache, string key, Func<string, TValue> valueFactory, DateTimeOffset absoluteExpiration, string regionName = null)
    {
        var lazy = new Lazy<TValue>(() => valueFactory(key));

        Lazy<TValue> item = (Lazy<TValue>) cache.AddOrGetExisting(key, lazy, absoluteExpiration, regionName) ?? lazy;

        return item.Value;
    }
#endif
}