委托到Lambda的进化: ()=> {} 这个lambda表达式就是一个无参数的委托及具体方法的组合体。

1.原始的委托 (.net 1.0)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
 
namespace WindowsFormsAppLINQ
{
    public partial class Form1 : Form
    {
        public delegate void MyDelegate();
        public Form1()
        {
            InitializeComponent();
 
            MyDelegate myDelegate = new MyDelegate(DoSomething);
 
            myDelegate();
 
        }
 
        public void DoSomething()
        {
            MessageBox.Show("Hello");
        }
    }
}

2.Action预定义委托, 节省了委托的定义.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsAppLINQ
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
 
            Action myDelegate = new Action(DoSomething);
 
            myDelegate();
        }
 
        public void DoSomething()
        {
            MessageBox.Show("Hello");
        }
    }
}

3.Lambda表达式, 再省掉方法定义.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsAppLINQ
{
    public partial class Form3 : Form
    {
        public Form3()
        {
            InitializeComponent();
 
            Action myDelegate = new Action(() => { MessageBox.Show("Hello"); });
 
            myDelegate();
        }
    }
}

4.一对小括号, 直接执行.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsAppLINQ
{
    public partial class Form4 : Form
    {
        public Form4()
        {
            InitializeComponent();
 
            new Action(() => { MessageBox.Show("Hello"); })();
        }
    }
}

总结，()=> {} 这个lambda表达式就是一个无参数的委托及具体方法的组合体，这是一个常规的套路，可以直接记住。