todo_json.cs in C#

A task list that survives restarts: JSON in, JSON out.

// todo_json: a tiny task list persisted as JSON in the temp directory
using System.Text.Json;

var path = Path.Combine(Path.GetTempPath(), "todo.json");
var opts = new JsonSerializerOptions { WriteIndented = true };

var items = File.Exists(path)
    ? JsonSerializer.Deserialize<List<Item>>(File.ReadAllText(path), opts)
    : new List<Item>();

items.Add(new Item("write the report", false));
items.Add(new Item("ship the release", false));
items[0] = items[0] with { Done = true };

File.WriteAllText(path, JsonSerializer.Serialize(items, opts));

var reloaded = JsonSerializer.Deserialize<List<Item>>(
    File.ReadAllText(path), opts);
foreach (var item in reloaded)
{
    var mark = item.Done ? "x" : " ";
    Console.WriteLine($"[{mark}] {item.Title}");
}
Console.WriteLine($"{reloaded.Count(i => !i.Done)} open");
File.Delete(path);

record Item(string Title, bool Done);

How it works

1. The file loads if present; a fresh list stands in if not.
2. with marks an item done without mutating the record.
3. Round-tripping through disk proves the persistence works.

Keywords and builtins used here

• Item
• bool
• false
• foreach
• in
• new
• record
• string
• true
• using
• var
• with

The run, in numbers

Lines

27

Characters to type

860

Tokens

199

Three-star pace

90 tpm

At the three-star pace of 90 tokens a minute, this run takes about 133 seconds.

Type this snippet

Step 2 of 2 in Encore, step 17 of 17 in The .NET library.

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