How to use this interface?

i found this interface and i want to use it. But i dont understand how to use the Create function...

namespace Microsoft.Extensions.Caching.Memory
{
    public interface IMemoryCache : IDisposable
    {
        ICacheEntry CreateEntry(object key);
        void Remove(object key);
        bool TryGetValue(object key, out object value);
    }
}

How to store something in CreateEntry when there is only the key not the value in the function call? How to store something in the key?

So i have this:

class RedisObjectTestCache : IMemoryCache
    {
        public ICacheEntry CreateEntry(object key)
        {
            Console.WriteLine("Created key: " + key);
            return new CacheEntryTest() { };
        }

        public void Dispose()
        {
            Console.WriteLine("Dispose");
            return;
        }

        public void Remove(object key)
        {
            Console.WriteLine("Removed key: " + key);
            return;
        }

        public bool TryGetValue(object key, out object value)
        {
            Console.WriteLine("Requested key: " + key);
            value = "";
            return false;
        }
    }

and then i call it with the framework:

QueryCacheManager.Cache = new RedisObjectTestCache();

Can i somehow get the value?