Using .NET 4's Lazy 实现单实例
Using .NET 4's Lazy<T> type
Explanation of the following code:
- If you're using .NET 4 (or higher) then you can use the System.Lazy<T> type to make the laziness really simple.
- All you need to do is pass a delegate to the constructor that calls the Singleton constructor, which is done most easily with a lambda expression.
- It also allows you to check whether or not the instance has been created with the IsValueCreated property.
public sealed class Singleton
{
private Singleton()
{
}
private static readonly Lazy<Singleton> lazy = new Lazy<Singleton>(() => new Singleton());
public static Singleton Instance
{
get
{
return lazy.Value;
}
}
}
Example:
The final example is here:
namespace Singleton
{
class Program
{
static void Main(string[] args)
{
Calculate.Instance.ValueOne = 10.5;
Calculate.Instance.ValueTwo = 5.5;
Console.WriteLine("Addition : " + Calculate.Instance.Addition());
Console.WriteLine("Subtraction : " + Calculate.Instance.Subtraction());
Console.WriteLine("Multiplication : " + Calculate.Instance.Multiplication());
Console.WriteLine("Division : " + Calculate.Instance.Division());
Console.WriteLine("\n----------------------\n");
Calculate.Instance.ValueTwo = 10.5;
Console.WriteLine("Addition : " + Calculate.Instance.Addition());
Console.WriteLine("Subtraction : " + Calculate.Instance.Subtraction());
Console.WriteLine("Multiplication : " + Calculate.Instance.Multiplication());
Console.WriteLine("Division : " + Calculate.Instance.Division());
Console.ReadLine();
}
}
public sealed class Calculate
{
private Calculate()
{
}
private static Calculate instance = null;
public static Calculate Instance
{
get
{
if (instance == null)
{
instance = new Calculate();
}
return instance;
}
}
public double ValueOne { get; set; }
public double ValueTwo { get; set; }
public double Addition()
{
return ValueOne + ValueTwo;
}
public double Subtraction()
{
return ValueOne - ValueTwo;
}
public double Multiplication()
{
return ValueOne * ValueTwo;
}
public double Division()
{
return ValueOne / ValueTwo;
}
}
}