Add DifferenceBetweenAsAndIs

Author: YSGStudyHards

DotNetGuidePractice/HelloDotNetGuide/CSharp语法/DifferenceBetweenAsAndIs.cs

@@ -0,0 +1,91 @@
+namespace HelloDotNetGuide.CSharp语法
+{
+    public class DifferenceBetweenAsAndIs
+    {
+        public static void IsOperator()
+        {
+            #region 检查对象是否是某个特定类型
+
+            string title = "Hello DotNetGuide";
+
+            if (title is string)
+            {
+                Console.WriteLine("是 string 类型");
+            }
+            else
+            {
+                Console.WriteLine("不是 string 类型");
+            }
+
+            if (title is not null)
+            {
+                Console.WriteLine("不为 null");
+            }
+            else
+            {
+                Console.WriteLine("为 null");
+            }
+
+            #endregion
+
+            #region 模式匹配
+
+            object obj = "追逐时光者";
+
+            if (obj is string str)
+            {
+                Console.WriteLine($" {str}");
+            }
+            else
+            {
+                Console.WriteLine("不是指定类型");
+            }
+
+            #endregion
+
+            #region 列表模式
+
+            int[] empty = [];
+            int[] one = [1];
+            int[] odd = [1, 3, 5];
+            int[] even = [2, 4, 6];
+            int[] fib = [1, 1, 2, 3, 5];
+
+            Console.WriteLine(odd is [1, _, 2, ..]);   // false
+            Console.WriteLine(fib is [1, _, 2, ..]);   // true
+            Console.WriteLine(fib is [_, 1, 2, 3, ..]);     // true
+            Console.WriteLine(fib is [.., 1, 2, 3, _]);     // true
+            Console.WriteLine(even is [2, _, 6]);     // true
+            Console.WriteLine(even is [2, .., 6]);    // true
+            Console.WriteLine(odd is [.., 3, 5]); // true
+            Console.WriteLine(even is [.., 3, 5]); // false
+            Console.WriteLine(fib is [.., 3, 5]); // true
+
+            #endregion
+        }
+
+        public static void AsOperator()
+        {
+            object title = "Hello DotNetGuide";
+            string str = title as string;
+            if (str != null)
+            {
+                Console.WriteLine("是 string 类型: " + str);
+            }
+            else
+            {
+                Console.WriteLine("不是 string 类型");
+            }
+
+            int? num = title as int?;
+            if (num.HasValue)
+            {
+                Console.WriteLine("是 int 类型: " + num.Value);
+            }
+            else
+            {
+                Console.WriteLine("不是 int 类型");
+            }
+        }
+    }
+}