Create TaskManager.cs

Author: danglinhanh

TaskManager.cs

@@ -0,0 +1,106 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text.Json;
+
+class TaskItem
+{
+    public int Id { get; set; }
+    public string Description { get; set; }
+}
+
+class TaskManager
+{
+    private const string FileName = "tasks.json";
+    private static List<TaskItem> tasks = new();
+
+    static void Main(string[] args)
+    {
+        LoadTasks();
+
+        if (args.Length == 0)
+        {
+            Console.WriteLine("Usage:");
+            Console.WriteLine("  add <description>");
+            Console.WriteLine("  list");
+            Console.WriteLine("  remove <id>");
+            return;
+        }
+
+        var command = args[0];
+
+        switch (command)
+        {
+            case "add":
+                AddTask(string.Join(" ", args[1..]));
+                break;
+            case "list":
+                ListTasks();
+                break;
+            case "remove":
+                if (args.Length < 2 || !int.TryParse(args[1], out int id))
+                {
+                    Console.WriteLine("Please provide a valid task ID.");
+                }
+                else
+                {
+                    RemoveTask(id);
+                }
+                break;
+            default:
+                Console.WriteLine("Unknown command.");
+                break;
+        }
+
+        SaveTasks();
+    }
+
+    static void LoadTasks()
+    {
+        if (File.Exists(FileName))
+        {
+            string json = File.ReadAllText(FileName);
+            tasks = JsonSerializer.Deserialize<List<TaskItem>>(json) ?? new();
+        }
+    }
+
+    static void SaveTasks()
+    {
+        string json = JsonSerializer.Serialize(tasks, new JsonSerializerOptions { WriteIndented = true });
+        File.WriteAllText(FileName, json);
+    }
+
+    static void AddTask(string description)
+    {
+        int nextId = tasks.Count == 0 ? 1 : tasks[^1].Id + 1;
+        tasks.Add(new TaskItem { Id = nextId, Description = description });
+        Console.WriteLine($"Added task #{nextId}: {description}");
+    }
+
+    static void ListTasks()
+    {
+        if (tasks.Count == 0)
+        {
+            Console.WriteLine("No tasks found.");
+            return;
+        }
+
+        foreach (var task in tasks)
+        {
+            Console.WriteLine($"[{task.Id}] {task.Description}");
+        }
+    }
+
+    static void RemoveTask(int id)
+    {
+        var task = tasks.Find(t => t.Id == id);
+        if (task == null)
+        {
+            Console.WriteLine("Task not found.");
+            return;
+        }
+
+        tasks.Remove(task);
+        Console.WriteLine($"Removed task #{id}");
+    }
+}