Lazy init objects stored in the current ASP.NET-request.

RequestLazy.cs

public class RequestLazy<T>
{
    private readonly Func<T> valueFactory;

    private readonly Func<IDictionary> storeFactory;

    internal RequestLazy(Func<T> valueFactory, string storeKey, Func<IDictionary> storeFactory)
    {
        this.storeFactory = storeFactory ?? (() => (HttpContext.Current != null) ? HttpContext.Current.Items : null);
        this.valueFactory = valueFactory ?? this.GetValue;
        this.StoreKey = string.Format("RequestLazy_{0}", storeKey ?? Guid.NewGuid().ToString());
    }

    public RequestLazy(string storeKey)
        : this(null, storeKey)
    {
    }

    public RequestLazy(Func<T> valueFactory, string storeKey = null)
        : this(valueFactory, storeKey, null)
    {
    }

    public string StoreKey { get; private set; }

    public T Value
    {
        get
        {
            if (this.ContextStore == null)
            {
                return this.valueFactory();
            }

            if (!this.ContextStore.Contains(this.StoreKey))
            {
                this.ContextStore[this.StoreKey] = this.valueFactory();
            }

            return this.GetValue();
        }
        set
        {
            if (this.ContextStore == null)
            {
                return;
            }

            this.ContextStore[this.StoreKey] = value;
        }
    }

    private IDictionary ContextStore
    {
        get
        {
            return this.storeFactory();
        }
    }

    public bool IsValueCreated
    {
        get
        {
            return this.ContextStore != null && this.ContextStore.Contains(this.StoreKey);
        }
    }

    public override string ToString()
    {
        return this.IsValueCreated ? this.Value.ToString() : "(Value not created)";
    }

    private T GetValue()
    {
        var item = this.ContextStore[this.StoreKey];
        return item is T ? (T)item : default(T);
    }
}