Path.Combine() / Path.GetFileName()

// Joins paths together. Automatically inserts the OS path separator.
Path.Combine(string path1, string path2)
Path.Combine(params string[] paths)

// Gets the filename (including extension) from a path.
Path.GetFileName(string path)

// Gets the filename without the extension from a path.
Path.GetFileNameWithoutExtension(string path)

// Gets the extension from a path (includes the leading dot).
Path.GetExtension(string path)

// Gets the directory portion from a path.
Path.GetDirectoryName(string path)

using System;
using System.IO;

// Join paths using Path.Combine().
string folder = @"C:\Users\akiba\documents";
string fileName = "report.txt";
string fullPath = Path.Combine(folder, fileName);
Console.WriteLine(fullPath); // C:\Users\akiba\documents\report.txt

// You can also join three or more paths.
string savePath = Path.Combine(@"C:\data", "2024", "01", "log.csv");
Console.WriteLine(savePath); // C:\data\2024\01\log.csv

// Extract the filename using Path.GetFileName().
string path = @"C:\Users\akiba\documents\report.txt";
Console.WriteLine(Path.GetFileName(path));                    // report.txt
Console.WriteLine(Path.GetFileNameWithoutExtension(path));    // report
Console.WriteLine(Path.GetExtension(path));                   // .txt
Console.WriteLine(Path.GetDirectoryName(path));               // C:\Users\akiba\documents

Path.Combine() is a safer way to join paths than concatenating strings directly. It automatically handles duplicate or missing separators, so the same code works on Windows, Linux, and Mac.

Manually concatenating paths with strings (e.g., path1 + "\\" + path2) is error-prone due to OS differences and separator mistakes, so always use Path.Combine() instead.

For reading and writing files, see File.ReadAllText() / File.WriteAllText().