C# 委托 Func 、 delegate、Action

参考

• 豆包
• https://blog.csdn.net/baihuomeng2210/article/details/101088283
• https://www.runoob.com/csharp/csharp-delegate.html
• https://learn.microsoft.com/zh-cn/dotnet/api/system.delegate?view=net-9.0#see-also
• https://www.cnblogs.com/liuhaorain/p/3911845.html
• https://blog.csdn.net/m0_65636467/article/details/127804807
• https://learn.microsoft.com/zh-cn/dotnet/api/system.func-1?view=net-9.0
• https://blog.csdn.net/hq0927/article/details/89948780
• https://segmentfault.com/a/1190000011934966
• https://www.cnblogs.com/ybqjymy/p/14281286.html

环境

软件/系统	版本	说明
Windows	windows 10 专业版 22H2 64 位操作系统, 基于 x64 的处理器
Microsoft Visual Studio	Community 2022 (64 位) - Current 版本 17.13.6
.NET	6.0

区别

委托的 Invoke 是同步调用

• delegate： 先声明再使用
• Func：内置委托，无需声明，直接使用，必须有返回值，最后一个泛型参数为返回类型
• Action： 内置委托，无需声明，直接使用，返回类型为 void

代码

1. Program.cs

   using System.Reflection.Metadata;
   using System.Xml.Linq;
   
   namespace ConsoleApp1
   {
   	public class Program
   	{
   		static void Main(string[] args)
   		{
   			Console.WriteLine("无参Action");
   			action = () => Console.WriteLine("无参Action");
   			action?.Invoke();
   			Console.WriteLine("有参Action");
   			action1 = (int parame) => Console.WriteLine("有参Action，参数为：" + parame);
   			action1?.Invoke(123);
   
   
   			Console.WriteLine("无参 Func");
   			func = () => 123;
   			Console.WriteLine(func?.Invoke());
   			Console.WriteLine("有参 Func，至多14个参数");
   			func1 = (int parame) => parame + 123;
   			Console.WriteLine(func1?.Invoke(123));
   
   
   			Console.WriteLine("无参 delegate");
   			Delegate1 delegate1 = Delegate1Method;
   			delegate1?.Invoke();
   			Console.WriteLine("有参 delegate");
   			Delegate2 delegate2 = Delegate2Method;
   			delegate2?.Invoke(456);
   			Console.WriteLine("有参 delegate，返回值");
   			Delegate3 delegate3 = Delegate3Method;
   			int result = delegate3?.Invoke(789) ?? 0;
   			Console.WriteLine("组合 delegate");
   			Delegate1 delegate4;
   			delegate4 = delegate1;
   			delegate4 += delegate1;
   			delegate4 += delegate1;
   			delegate4 += delegate1;
   			delegate4?.Invoke();
   
   
   
   
   		}
   
   		public static Action action;
   		public static Action<int> action1;
   
   		public static Func<int>? func;
   		public static Func<int, int>? func1;
   		public delegate void Delegate1();
   		public delegate void Delegate2(int parame);
   		public delegate int Delegate3(int parame);
   		//
   		static void Delegate1Method()
   		{
   			Console.WriteLine("无参委托");
   		}
   		static void Delegate2Method(int parame)
   		{
   			Console.WriteLine("有参委托，参数为：" + parame);
   		}
   		static int Delegate3Method(int parame)
   		{
   			Console.WriteLine("有参委托，参数为：" + parame);
   			return parame + 123;
   		}
   
   
   
   	}
   }