添加Lesson8

2025-10-14 16:07:14 +08:00
parent 3c4123d514
commit c86de4e6be
7 changed files with 240 additions and 0 deletions
@@ -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 +1,89 @@
+using System.Collections.Generic;
+namespace Lesson8_Dictionary
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            #region 知识点一 Dictionary本质
+            //可以将Dictionary理解为 拥有泛型的Hashtable
+            //他也是极于剑的哈希代码组织起来的 键/值对
+            //键值对类型从Hashtable的object变为了可以自己指定的泛型
+            #endregion
+
+            #region 知识点二 声明
+            Dictionary<int, string> dictionary = new Dictionary<int, string>();
+            #endregion
+
+            #region 知识点三 增删查改
+            #region 增
+            //注意：不能出现相同键
+            dictionary.Add(1, "111");
+            dictionary.Add(2, "222");
+            dictionary.Add(3, "333");
+            #endregion
+
+            #region 删
+            //1.只能通过键去删除
+            // 删除不存在的键 无反应
+            dictionary.Remove(1);
+            dictionary.Remove(4);
+            //2.清空
+            dictionary.Clear();
+            #endregion
+
+            #region 查
+            //1.通过键查看值
+            //注意：找不到直接报错，而不是像hashtable一样无反应
+            dictionary.Add(1, "111");
+            dictionary.Add(2, "222");
+            dictionary.Add(3, "333");
+            Console.WriteLine(dictionary[2]);//"222"
+            //Console.WriteLine(dictionary[4]);//不会像hashtable一样无反应而是直接报错
+            //2.查看是否存在
+            // 根据键检测
+            if (dictionary.ContainsKey(1) )
+            {
+                Console.WriteLine("存在键为1的键值对");
+            }
+            // 根据值检测
+            if (dictionary.ContainsValue("111"))
+            {
+                Console.WriteLine("存在值为111的键值对");
+            }
+            #endregion
+
+            #region 改
+            Console.WriteLine(dictionary[1]);
+            dictionary[1] = "999";
+            Console.WriteLine(dictionary[1]);
+            #endregion
+            #endregion
+
+            #region 知识点四 遍历啊
+            Console.WriteLine("---------------------------");
+            //长度
+            Console.WriteLine(dictionary.Count);
+            //1.遍历所有键
+            Console.WriteLine("---------------------------");
+            foreach (int item in dictionary.Keys)
+            {
+                Console.WriteLine(item);
+                Console.WriteLine(dictionary[item]);
+            }
+            //2.遍历所有值
+            Console.WriteLine("---------------------------");
+            foreach (string item in dictionary.Values)
+            {
+                Console.WriteLine(item);
+            }
+            //3.键值对一起遍历
+            Console.WriteLine("---------------------------");
+            foreach (KeyValuePair<int, string> pair in dictionary)
+            {
+                Console.WriteLine($"键：{pair.Key}  值:{pair.Value}");
+            }
+            #endregion
+        }
+    }
+}