How do you get the file size in C#?

Question

I need a way to get the size of a file using C#, and not the size on disk. How is this possible?

Currently I have this loop

foreach (FileInfo file in downloadedMessageInfo.GetFiles())
{
    //file.Length (will this work)
}

Will this return the size or the size on disk?

Wahhabi

Related, but for VB.NET: Determining file size in VB.NET, – Eastbound

Answer 1

FileInfo.Length will return the length of file, in bytes (not size on disk), so this is what you are looking for, I think.

Gilding

Also: social.msdn.microsoft.com/Forums/en-US/Vsexpressvcs/thread/… this is a discussion about how to get "the other value", which is size on disk. – Unlimber

There is no method "FileInfo.Length"! Remember that you specified call of STATIC METHOD. Real answer is new FileInfo(path).Length what can be heavy for mass operation. – Harim

FWIW @Harim - Yes and No. FileInfo.Length is how the doc refers to the property, even though it is not static. The answer is relative to the code in question. Consider how one typically does a "mass operation" - via the directory info: ... new DirectoryInfo(...).GetFiles(); A collection of FileInfos is created for you. Getting Length of all those files is lightweight. – Honeysweet

@ToolmakerSteve: MS docs is well-known rubbish, don't refer it as a "normal way". Newbies will be confused when they see call to static method and obviously it doesn't exist. GetFiles() is only one of ways to get list of files. Names could be autogenerated (like "pic15.jpg", "pic16.jpg"...) - then you need to call FileInfo every time. In any case OS keeps cache of directories and getting length MUST NOT be heavy operation as "create object" - length can be obtained directly by call like FileInfo.GetLength(string fileName). It's WAY more convenient and suits to many casual tasks. – Harim

@Viincent - "Names could be autogenerated (like "pic15.jpg", "pic16.jpg"...) - then you need to call FileInfo every time. " That's almost never necessary, for a "mass operation". Extract the directory path of all the file paths, into a HashSet. I'd love to know about a static method that gives Length of file. What environment are you in, that has FileInfo.GetLength? Neither Google nor Intellisense is giving me a hit for any static member, on either File or FileInfo, that gives file length. – Honeysweet

Answer 2

If you have already a file path as input, this is the code you need:

long length = new System.IO.FileInfo(path).Length;

Artful

Surround it with try/catch block and check all possible exceptions as described here: SecurityException, UnauthorizedAccessException, PathTooLongException, NotSupportedException and - dependend on your use case - ArgumentNullException and ArgumentException – Googins

Answer 3

FileInfo.Length will do the trick (per MSDN it "[g]ets the size, in bytes, of the current file.") There is a nice page on MSDN on common I/O tasks.

Alderman

Answer 4

MSDN FileInfo.Length says that it is "the size of the current file in bytes."

My typical Google search for something like this is: msdn FileInfo

Polyphyletic

Answer 5

The FileInfo class' Length property returns the size of the file (not the size on disk). If you want a formatted file size (i.e. 15 KB) rather than a long byte value you can use CSharpLib, a package I've made that adds more functionality to the FileInfo class. Here's an example:

using CSharpLib;
FileInfo info = new FileInfo("sample.txt");
Console.WriteLine(info.FormatBytes());  // Output: 15 MB

Creeper

Answer 6

It returns the file contents length

Marx

Answer 7

Size on disk might be different, if you move the file to another filesystem (FAT16, NTFS, EXT3, etc)

As other answerers have said, this will give you the size in bytes, not the size on disk.

Marotta

Answer 8

long l = new System.IO.FileInfo(path).Length;
string l_ = Formatter(l); // Example: "67 Mb"

//

public string Formatter(long input)
    {
        string output;
        switch (input.ToString().Length)
        {
            case > 12:
                output = input / 1000000000000 + " Tb";
                break;
            case > 9:
                output = input / 1000000000 + " Gb";
                break;
            case > 6:
                output = input / 1000000 + " Mb";
                break;
            case > 3:
                output = input / 1000 + " Kb";
                break;
            default:
                output = input + " b";
                break;
        }
        return output;
    }

Uniformity

Answer 9

Thanks to JLRishe's answer. Here is my edited code for your convenience.

public static class QuickImgSize
{
    //https://mcmap.net/q/81994/-does-net-provide-an-easy-way-convert-bytes-to-kb-mb-gb-etc
    private static string[] S_SIZE_SUFFIXES =
               { "bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };
    private static string SizeSuffix(long value, int decimalPlaces = 2)
    {
        if (decimalPlaces < 0) { throw new ArgumentOutOfRangeException("decimalPlaces"); }
        if (value < 0) { return "-" + SizeSuffix(-value, decimalPlaces); }
        if (value == 0) { return string.Format("{0:n" + decimalPlaces + "} bytes", 0); }

        // mag is 0 for bytes, 1 for KB, 2, for MB, etc.
        int mag = (int)Math.Log(value, 1024);

        // 1L << (mag * 10) == 2 ^ (10 * mag) 
        // [i.e. the number of bytes in the unit corresponding to mag]
        decimal adjustedSize = (decimal)value / (1L << (mag * 10));

        // make adjustment when the value is large enough that
        // it would round up to 1000 or more
        if (Math.Round(adjustedSize, decimalPlaces) >= 1000)
        {
            mag += 1;
            adjustedSize /= 1024;
        }

        return string.Format("{0:n" + decimalPlaces + "} {1}",
            adjustedSize,
            S_SIZE_SUFFIXES[mag]);
    }

    public static string GetFileSize(string szPath)
    {
        var fileInfo = new FileInfo(szPath);
        return SizeSuffix(fileInfo.Length);
    }
}

Usage:

Console.WriteLine(QuickImgSize.GetFileSize(@"C:\Program Files (x86)\Mozilla Firefox\firefox.exe"));

Mariel

Would you explain your "edit"? – Trincomalee