Instance, SingleInstance, MultiInstance

Instance.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace EifelMono
{
    public class Instance<T>
    {
        public Instance()
        {
        }
        public Instance(CreateDelegate onCreateInstance)
            : this()
        {
            OnCreateInstance = onCreateInstance;
        }
        public delegate T CreateDelegate();
        public CreateDelegate OnCreateInstance = null;

        public bool AllwaysCreateNewInstance = false;
        protected T m_Value = default(T);
        public bool IsValueCreated
        {
            get
            {
                return m_Value != null;
            }
        }

        protected T CreateInstance()
        {
            try
            {
                return OnCreateInstance != null ? OnCreateInstance() : Activator.CreateInstance<T>();
            }
            catch (Exception ex)
            {
                Log.HandleException(ex);
                return default(T);
            }
        }

        public T Value
        {
            get
            {
                if (AllwaysCreateNewInstance)
                    m_Value = CreateInstance();
                else
                    if (!IsValueCreated)
                        m_Value = CreateInstance();
                return m_Value;
            }
        }

    }

    public class SingleInstance<T> : Instance<T>
    {
        public SingleInstance()
            : base()
        {
            AllwaysCreateNewInstance = false;
        }
        public SingleInstance(CreateDelegate onCreateInstance)
            : base(onCreateInstance)
        {
            AllwaysCreateNewInstance = false;
        }
    }
    public class MultiInstance<T> : Instance<T>
    {
        public MultiInstance()
            : base()
        {
            AllwaysCreateNewInstance = true;
        }
        public MultiInstance(CreateDelegate onCreateInstance)
            : base(onCreateInstance)
        {
            AllwaysCreateNewInstance = true;
        }
    }
}