FileInfo Length

FileInfo has a Length property. It returns the size of a file in bytes. We use FileInfo and the Length property to measure file sizes.

To get all FileInfos from a directory, we can use the GetFileSystemInfos method. This can make some file-handling code clearer.

Example

FileInfo is useful if your program modifies files, and you want to see how many bytes have been added or removed. The Length often can be safely cast to an int.

using System;
using System.IO;

const string fileName = @"C:\programs\file.txt";

// Part 1: create new FileInfo get Length.
FileInfo info = new FileInfo(fileName);
long length = info.Length;

// Part 2: print length in bytes.
Console.WriteLine("LENGTH IN BYTES: {0}", length);
LENGTH IN BYTES: 60

GetFileSystemInfos

We can get an array of FileSystemInfo and then get each individual FileInfo. We use the GetFileSystemInfos method.

using System;
using System.IO;

class Program
{
    static int GetDirectorySize(string path)
    {
        // Part 1: get info.
        DirectoryInfo directoryInfo = new DirectoryInfo(path);
        FileSystemInfo[] array = directoryInfo.GetFileSystemInfos();

        // Part 2: sum all FileInfo Lengths.
        int sum = 0;
        for (int i = 0; i < array.Length; i++)
        {
            FileInfo fileInfo = array[i] as FileInfo;
            if (fileInfo != null)
            {
                sum += (int)fileInfo.Length;
            }
        }
        return sum;
    }

    public static void Main()
    {
        Console.WriteLine("SIZE: {0}", GetDirectorySize(@"C:\programs\"));
    }
}
SIZE: 96035

Exceptions

It is common to have to handle exceptions when files are being used. They may be missing, corrupted or not accessible because of security issues.

We retrieved the length of files using the FileInfo class and its Length property. This uses a long value and does not require you to read and process the entire file.