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📜 WAYPOINT LESSON

Path, File, Directory

⭐ beginner⏳ 12 min read📍 Lesson 54 of 85

Path manipulates names, File/Directory manipulate reality — and combining them badly is a classic bug.

Three static classes

  • Path — string surgery on file names: Combine, GetFileName, GetExtension. It touches no disk.
  • File — one-shot operations: WriteAllText, ReadAllText, AppendAllText, Exists, Delete.
  • Directory — folders: CreateDirectory, GetFiles, Exists.
string path = Path.Combine("/tmp", "cj", "notes.txt");
Directory.CreateDirectory(Path.GetDirectoryName(path));   // /tmp/cj
File.WriteAllText(path, "hello\n");
string again = File.ReadAllText(path);

The rules that prevent bugs

Path.Combine("a", "/b") — an absolute second argument replaces the first; that's defined behavior, not a bug, but it surprises people. And File.WriteAllText overwrites without asking: a save-one-line bug can destroy yesterday's data. Check File.Exists when history matters, and prefer AppendAllText for logs.