add Programmyday form github

ExtensionMethods/ExtensionMethods.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

ExtensionMethods/Program.cs

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+using System.Text;
+
+namespace ExtensionMethods
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            string text = "Abra Kadabra";
+            Console.WriteLine(text);
+            Console.WriteLine(text.SwitchCase());
+        }
+    }
+    static class StringExtensions
+    {
+        public static string SwitchCase(this string s)
+        {
+            StringBuilder sb = new StringBuilder();
+            foreach (char c in s)
+            {
+                sb.Append(char.IsUpper(c) ? char.ToLower(c) : char.ToUpper(c));
+            }
+            return sb.ToString();
+        }
+    }
+
+}