Calculate the Size of Directory

The DirectoryInfo class does not provide any property that returns size information. However, you can easily calculate the size of all files contained in a directory using the FileInfo.Length property.

Here's a method that uses this technique and optionally examines contained directories recursively:

using System;
using System.IO;

public class FileSystemUtil {

    public static long CalculateDirectorySize(DirectoryInfo directory,
      bool includeSubdirectories) {

        long totalSize = 0;

        // Examine all contained files.
        FileInfo[] files = directory.GetFiles();
        foreach (FileInfo file in files) {
            totalSize += file.Length;
        }

        // Examine all contained directories.
        if (includeSubdirectories) {

            DirectoryInfo[] dirs = directory.GetDirectories();
            foreach (DirectoryInfo dir in dirs) {
                totalSize += CalculateDirectorySize(dir, true);
            }
        }

        return totalSize;
    }
}

Here's a simple test application:

using System;
using System.IO;

public class CalculateDirSize {

    private static void Main(string[] args) {

        if (args.Length == 0) {

            Console.WriteLine("Please supply a directory path.");
            return;
        }

        DirectoryInfo dir = new DirectoryInfo(args[0]);
        Console.WriteLine("Total size: " + 
          FileSystemUtil.CalculateDirectorySize(dir, true).ToString() + 
          " bytes.");
        Console.ReadLine();
    }
}

Technorati : C# Directory size calculation