FileInfo

This type gets information about a file. It retrieves information about a specific file or directory from the file system.

Type details

The FileInfo type provides many methods and properties. These help us detect the status of a file. We can get Length or dates.

Attributes

Every file on the Windows File system stores a set of attributes. You can detect its visibility, whether it is a directory, and if it is read-only.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Get Attributes for file.
        FileInfo info = new FileInfo("C:\\file.txt");
        FileAttributes attributes = info.Attributes;
        Console.WriteLine(attributes);

        // Get Attributes for directory.
        info = new FileInfo("C:\\");
        attributes = info.Attributes;
        Console.WriteLine(attributes);
    }
}
Archive
Hidden, System, Directory

Values, FileAttributes

There are many different flags on the FileAttributes enum. Some of them, such as ReadOnly, can be retrieved in other ways. This is true for many .NET methods.

FileAttributes.Archive
FileAttributes.Compressed
FileAttributes.Device
FileAttributes.Directory
FileAttributes.Encrypted
FileAttributes.Hidden
FileAttributes.Normal
FileAttributes.NotContentIndexed
FileAttributes.Offline
FileAttributes.ReadOnly
FileAttributes.ReparsePoint
FileAttributes.SparseFile
FileAttributes.System
FileAttributes.Temporary

Times

The Windows file system keeps track of a file's creation time, its last access, and its last write time. We can get this information with the FileInfo type.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        FileInfo info = new FileInfo("C:\\file.txt");

        DateTime time = info.CreationTime;
        Console.WriteLine(time);

        time = info.LastAccessTime;
        Console.WriteLine(time);

        time = info.LastWriteTime;
        Console.WriteLine(time);
    }
}
7/17/2010 9:48:48 AM
7/17/2010 9:48:48 AM
8/18/2010 4:48:27 PM

Directory

Every file on the file system is stored in a containing directory. You can quickly access this DirectoryInfo with the Directory property.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Get file info.
        FileInfo info = new FileInfo("C:\\file.txt");

        // Access parent directory.
        DirectoryInfo dir = info.Directory;
        Console.WriteLine(dir.Name);

        // Get directory name.
        string name = info.DirectoryName;
        Console.WriteLine(name);
    }
}
C:\
C:\

Exists

You can create a FileInfo for a file that does not exist. To see if the file does not exist, you can test the result of the Exists property. It is true or false.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Get file info.
        FileInfo info = new FileInfo("C:\\does-not-exist.txt");
        bool exists = info.Exists;
        Console.WriteLine(exists);
    }
}
False

Name, extension

Typically, you should use the Path type to get file name parts such as the name or extension. But the FileInfo type provides ways to get some of these parts as well.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Get file info.
        FileInfo info = new FileInfo("C:\\file.txt");

        string name = info.Name;
        string fullName = info.FullName;
        string extension = info.Extension; // Has period

        Console.WriteLine(name);
        Console.WriteLine(fullName);
        Console.WriteLine(extension);
    }
}
file.txt
C:\file.txt
.txt

Length

How many bytes are in a file? The Length property on the FileInfo type provides a way to effectively determine this. It returns a figure in bytes.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        FileInfo info = new FileInfo("C:\\a");
        long value = info.Length;
        Console.WriteLine(value);
    }
}
5320683

MoveTo

You can use the FileInfo type to rename (move) a file. This should reduce copying in the file system over creating a duplicate file and deleting the original.

using System.IO;

class Program
{
    static void Main()
    {
        // Write the specified file with some text.
        File.WriteAllText("C:\\test1.txt", "A");

        // Create a FileInfo instance for the specified path.
        // ... Then move the specified file to a new file path.
        FileInfo info = new FileInfo("C:\\test1.txt");
        info.MoveTo("C:\\test2.txt");
    }
}
1. One file is created.
2. The file is renamed to a new name.

Text

If your FileInfo points to a text file, it is a good idea to use the AppendText, CreateText, and OpenText methods to acquire a StreamWriter or StreamReader instance.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // This file will have a new line at the end.
        FileInfo info = new FileInfo("C:\\file.txt");
        using (StreamWriter writer = info.AppendText())
        {
            writer.WriteLine("Line");
        }

        // This file will have the word New in it.
        info = new FileInfo("C:\\new.txt");
        using (StreamWriter writer = info.CreateText())
        {
            writer.WriteLine("New");
        }

        // Get a StreamReader with OpenText.
        using (StreamReader reader = info.OpenText())
        {
            Console.WriteLine(reader.ReadToEnd());
        }
    }
}
New

Security

The FileInfo type provides a way to retrieve and store security information on the file system. This is most important for multi-user servers that have restricted information.

GetAccessControl
SetAccessControl

GetLifetimeService
InitializeLifetimeService

Encrypt

The Encrypt and Decrypt methods are not available on all Windows computers. If you choose to use them, you can wrap them in exception-handling.

Unhandled Exception: System.IO.IOException: The request is not supported.

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.File.Encrypt(String path)
   at System.IO.FileInfo.Encrypt()
   at Program.Main() in C:\...Program.cs:line 10

ReadOnly, IsReadOnly

If you are trying to determine if a file is read-only, you can use the IsReadOnly method instead of the FileAttributes.ReadOnly constant.

FileStream

Sometimes, we deal with a non-text file and want to use types such as BinaryReader or BinaryWriter on a file. This is possible with a FileStream.

A summary

By providing these properties and methods, the FileInfo type makes it easy to get information from the file system about a file.