Check if a folder exists in .NET with C# / VB

At least when your program launches, check if directories you need exist; in the case of network folders, they may exist but be either unavailable, or not properly reconnected to. The methods and members used in this tutorial belong to the System.IO namespace, needed at the top: using System.IO;
Tip: you can also check if a file exists, and optionally create it.
In VB, you don't need to worry about escaping file paths; in C#, either escape every single backslash you encounter ("\"), or use the "@" symbol to declare a string literal: string folder = "C:\\Projects\\Notes"; // escaped path // Or, the easier way: string folder = @"C:\Projects\Notes"; // string literal
Save time with special (system) folders by using and combining environment variables: string folder = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) + "\\MyFolder";
To check if the directory exists, use this boolean construct: if( Directory.Exists( folder ) ) // Folder exists - write useful code here... else MessageBox.Show("This folder doesn't exist!");
Note: you can of course directly pass the path as argument; we didn't here to keep things simple.
You can now get a list of file by extension by passing a filter ("*.txt") to the GetFiles() method. To check how many files a folder contains, retrieve the size of the returned array: int numberOfTextFiles = Directory.GetFiles( folder, "*.txt" ).Length;

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