FileInfo.Decrypt Method

Definition

Namespace:

System.IO

Assemblies:

netstandard.dll, System.Runtime.dll

Source:

FileInfo.cs

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

C#

[System.Runtime.Versioning.SupportedOSPlatform("windows")]
public void Decrypt();

Attributes

SupportedOSPlatformAttribute

Exceptions

DriveNotFoundException

An invalid drive was specified.

FileNotFoundException

The file described by the current FileInfo object could not be found.

IOException

An I/O error occurred while opening the file.

NotSupportedException

The file system is not NTFS.

PlatformNotSupportedException

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

UnauthorizedAccessException

The file described by the current FileInfo object is read-only.

-or-

This operation is not supported on the current platform.

-or-

The caller does not have the required permission.

Examples

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

C#

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

namespace FileSystemExample
{
    class FileExample
    {
        public static void Main()
        {
            try
            {
                string FileName = @"c:\MyTest.txt";

                Console.WriteLine("Encrypt " + FileName);

                // Encrypt the file.
                AddEncryption(FileName);

                Console.WriteLine("Decrypt " + FileName);

                // Decrypt the file.
                RemoveEncryption(FileName);

                Console.WriteLine("Done");
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
        }

        public static void AddEncryption(string FileName)
        {
            // Create a new FileInfo object.
            FileInfo fInfo = new FileInfo(FileName);
            if (!fInfo.Exists)
            {
                //Create the file.
                fInfo.Create();
            }
            // Add encryption.
            fInfo.Encrypt();
        }

        public static void RemoveEncryption(string FileName)
        {
            // Create a new FileInfo object.
            FileInfo fInfo = new FileInfo(FileName);
            if (!fInfo.Exists)
            {
                //Create the file.
                fInfo.Create();
            }
            // Remove encryption.
            fInfo.Decrypt();
        }
    }
}

//This code produces output similar to the following;
//results may vary based on the computer/file structure/etc.:
//
//Encrypt c:\MyTest.txt
//Decrypt c:\MyTest.txt
//Done

Remarks

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.

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.

Applies to