添加Lesson15

2025-10-20 11:12:14 +08:00
parent b4d3ced472
commit b1d4959956
5 changed files with 179 additions and 0 deletions
@@ -61,6 +61,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Lesson14_匿名函数", "Le
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Lesson14_匿名函数练习", "Lesson14_匿名函数练习\Lesson14_匿名函数练习.csproj", "{9030BA7A-FDFA-4F88-869E-918589104831}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Lesson15_lambda表达式", "Lesson15_lambad表达式\Lesson15_lambda表达式.csproj", "{50810F24-0145-43C6-AE3E-1D99D0583AB8}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Lesson15_lambda表达式练习", "Lesson15_lambad表达式练习\Lesson15_lambda表达式练习.csproj", "{E0931580-D76C-4434-B059-149AEED828ED}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -183,6 +187,14 @@ Global
 		{9030BA7A-FDFA-4F88-869E-918589104831}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{9030BA7A-FDFA-4F88-869E-918589104831}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{9030BA7A-FDFA-4F88-869E-918589104831}.Release|Any CPU.Build.0 = Release|Any CPU
+		{50810F24-0145-43C6-AE3E-1D99D0583AB8}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{50810F24-0145-43C6-AE3E-1D99D0583AB8}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{50810F24-0145-43C6-AE3E-1D99D0583AB8}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{50810F24-0145-43C6-AE3E-1D99D0583AB8}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E0931580-D76C-4434-B059-149AEED828ED}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E0931580-D76C-4434-B059-149AEED828ED}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E0931580-D76C-4434-B059-149AEED828ED}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E0931580-D76C-4434-B059-149AEED828ED}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>
@@ -0,0 +1,97 @@
+namespace Lesson15_lambda表达式
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            #region 知识点一 什么时lambda表达式
+            //可以将lambda表达式理解为 匿名函数的简写
+            //它除了写法不同外
+            //使用上和匿名函数是一样的
+            //都是配合委托类型使用的
+            #endregion
+
+            #region 知识点二 lambda表达式的语法
+            //匿名函数
+            //delegate(参数列表){函数体};
+
+            //lambda表达式
+            //(参数列表)=>{函数体};
+            #endregion
+
+            #region 知识点三 使用
+            //1.无参无返回值的lambda表达式
+            Action a = () =>
+            {
+                Console.WriteLine("无参无返回的lambda表达式函数");
+            };
+            a();
+
+            //2.有参无返回值的lambda表达式
+            Action<int> a2 = (int i1) =>
+            {
+                Console.WriteLine($"有参无返回的lambda表达式 参数i1:{i1}");
+            };
+            a2(100);
+
+            //3.有参的lambda表达式，甚至参数类型都可以省略 参数类型和委托或事件容器一致
+            Action<int> a3 = (i1) =>
+            {
+                Console.WriteLine($"有参无返回的lambda表达式 参数i1:{i1}");
+            };
+            a3(200);
+
+            //4.有返回值的lambda表达式
+            Func<int, int, int> f = (i1, i2) =>
+            {
+                Console.WriteLine($"有返回的lambda，将返回{i1}与{i2}相加");
+                return i1 + i2;
+            };
+            Console.WriteLine(f(10, 20));
+            #endregion
+
+            Test t = new Test();
+            t.Dosomething();
+        }
+    }
+    #region 知识点四 闭包
+    //内层的函数可以引用包含在它外层的变量
+    //即使外层函数已经执行完毕
+    //注意：
+    //该变量提供的值并不是变量创建时的值，而是在父函数范围内最后一次被修改的值
+    #endregion
+
+    class Test
+    {
+        public event Action action;
+        public Test()
+        {
+            int value = 10;
+            //这里就是一个闭包的例子
+            //因为 当构造函数执行完毕后 value变量的生命周期应该结束了
+            //但是由于action引用了value变量
+            //所以value变量的生命周期被延长了
+            action = () =>
+            {
+                Console.WriteLine($"闭包value的值为:{value}");
+            };
+            for (int i = 0; i < 10; i++)
+            {
+                int index = i;//解决闭包问题的常用方法
+                //每次都是新创建的index变量，所以可以保存当时的值
+                //但是i是在循环里的，所以每次循环都是同一个i变量，所以最终闭包引用的i变量的值就是循环结束时的值10
+                action += () =>
+                {
+                    Console.WriteLine($"闭包循环i的值为:{i}");
+                    Console.WriteLine($"闭包循环index的值为:{index}");
+                };
+
+            }
+        }
+
+        public void Dosomething()
+        {
+            action();
+        }
+    }
+}
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>
@@ -0,0 +1,50 @@
+namespace Lesson15_lambda表达式练习
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            a1()();
+            a2()();
+        }
+        
+        public static Action a1()
+        {
+            Action action = null;
+            for (int i = 1; i <= 10; i++)
+            {
+                int index = i;
+                action += delegate()
+                {
+                    Console.WriteLine(index);
+                };
+            }
+            return action;
+        }
+        public static Action a2()
+        {
+            Action action = null;
+            for (int i = 1; i <= 10; i++)
+            {
+                int index = i;
+                action += () => Show(index);
+            }
+            return action;
+        }
+        public static Action a3()
+        {
+            Action action = null;
+            for (int i = 1; i <= 10; i++)
+            {
+                int index = i;
+                action += () => Show(index);
+            }
+            return action;
+        }
+        static void Show(int x)
+        {
+            Console.WriteLine(x);
+        }
+    }
+
+}