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File.Decrypt Method

Decrypts a file that was encrypted by the current account using the Encrypt method.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)

public static void Decrypt(
	string path


Type: System.String

A path that describes a file to decrypt.


The path parameter is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.


The path parameter is null.


An invalid drive was specified.


The file described by the path parameter could not be found.


An I/O error occurred while opening the file. For example, the encrypted file is already open.


This operation is not supported on the current platform.


The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.


The current operating system is not Microsoft Windows NT or later.


The file system is not NTFS.


The path parameter specified a file that is read-only.


This operation is not supported on the current platform.


The path parameter specified a directory.


The caller does not have the required permission.

The Decrypt method allows you to decrypt a file that was encrypted using the Encrypt method. The Decrypt method can decrypt only files that were encrypted using the current user account.

The Decrypt method requires exclusive access to the file being decrypted, and will raise an exception if another process is using the file. If the file is not encrypted, Decrypt will return a nonzero value, which indicates success.

Both the Encrypt method and the Decrypt method use the cryptographic service provider (CSP) installed on the computer and the file encryption keys of the process calling the method.

The current file system must be formatted as NTFS and the current operating system must be Microsoft Windows NT or later.

The following code example uses the Encrypt method and the Decrypt method to encrypt and then decrypt a file.

using System;
using System.IO;
using System.Security.AccessControl;

namespace FileSystemExample
    class FileExample
        public static void Main()
                string FileName = "test.xml";

                Console.WriteLine("Encrypt " + FileName);

                // Encrypt the file.

                Console.WriteLine("Decrypt " + FileName);

                // Decrypt the file.

            catch (Exception e)


        // Encrypt a file. 
        public static void AddEncryption(string FileName)



        // Decrypt a file. 
        public static void RemoveEncryption(string FileName)

  • FileIOPermission 

    for permission to read and write to the file described by the path parameter. Associated enumerations: Read, Write

    Security action: Demand.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0