Add AgeCalculator sample app

core/console-apps/AgeCalculator/AgeCalculator.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+  </PropertyGroup>
+
+</Project>

core/console-apps/AgeCalculator/Program.cs

@@ -0,0 +1,35 @@
+using System;
+
+namespace AgeCalculator
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine("=== Age Calculator ===");
+
+            Console.Write("Enter your date of birth (yyyy-mm-dd): ");
+            string input = Console.ReadLine();
+
+            if (DateTime.TryParse(input, out DateTime dob))
+            {
+                DateTime today = DateTime.Today;
+                int age = today.Year - dob.Year;
+                if (dob > today.AddYears(-age)) age--;
+
+                Console.WriteLine($"You are {age} years old.");
+
+                DateTime nextBirthday = dob.AddYears(age + 1);
+                int daysUntil = (nextBirthday - today).Days;
+                Console.WriteLine($"Your next birthday is in {daysUntil} days.");
+            }
+            else
+            {
+                Console.WriteLine("Invalid date format. Please use yyyy-mm-dd.");
+            }
+
+            Console.WriteLine("Press any key to exit...");
+            Console.ReadKey();
+        }
+    }
+}

core/console-apps/AgeCalculator/README.md

@@ -0,0 +1,20 @@
+# Age Calculator Sample
+
+This is a beginner-friendly .NET 8 console app that calculates a user's age and days until their next birthday based on their date of birth input.
+
+## Key Features
+
+- Reads user input for date of birth
+- Calculates current age
+- Displays days until next birthday
+- Includes basic error handling for invalid input
+
+## Build and Run
+
+To build and run the sample, type the following command:
+
+`dotnet run`
+
+`dotnet run` builds the sample and runs the output assembly. It implicitly calls `dotnet restore` on .NET Core 2.0 and later versions. If you're using a .NET Core 1.x SDK, you first have to call `dotnet restore` yourself.
+
+**Note:** Starting with .NET Core 2.0 SDK, you don't have to run [`dotnet restore`](https://docs.microsoft.com/dotnet/core/tools/dotnet-restore) because it's run implicitly by all commands that require a restore to occur, such as `dotnet new`, `dotnet build` and `dotnet run`. It's still a valid command in certain scenarios where doing an explicit restore makes sense, such as [continuous integration builds in Azure DevOps Services](https://docs.microsoft.com/azure/devops/build-release/apps/aspnet/build-aspnet-core) or in build systems that need to explicitly control the time at which the restore occurs.