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FromBase64Transform Class

Converts a CryptoStream from base 64.


Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)

public class FromBase64Transform : ICryptoTransform, 

The FromBase64Transform type exposes the following members.

Public methodFromBase64Transform()Initializes a new instance of the FromBase64Transform class.
Public methodFromBase64Transform(FromBase64TransformMode)Initializes a new instance of the FromBase64Transform class with the specified transformation mode.

Public propertyCanReuseTransformGets a value indicating whether the current transform can be reused.
Public propertyCanTransformMultipleBlocksGets a value that indicates whether multiple blocks can be transformed.
Public propertyInputBlockSizeGets the input block size.
Public propertyOutputBlockSizeGets the output block size.

Public methodClearReleases all resources used by the FromBase64Transform.
Public methodDispose()Releases all resources used by the current instance of the FromBase64Transform class.
Protected methodDispose(Boolean)Releases the unmanaged resources used by the FromBase64Transform and optionally releases the managed resources.
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeReleases the unmanaged resources used by the FromBase64Transform. (Overrides Object.Finalize().)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodTransformBlockConverts the specified region of the input byte array from base 64 and copies the result to the specified region of the output byte array.
Public methodTransformFinalBlockConverts the specified region of the specified byte array from base 64.

Base 64 Content-Transfer-Encoding represents arbitrary bit sequences in a form that is not human readable.

The following example decrypts a base 64-encoded file to an output text file.

using System;
using System.IO;
using System.Security.Cryptography;

class Members
    static void Main(string[] args)
        string appPath = (System.IO.Directory.GetCurrentDirectory() );
        appPath = appPath + "..\\\\..\\\\..\\";
        // Insert your file names into this method call.
        EncodeFromFile(appPath + "program.cs", appPath + "code.enc");
        DecodeFromFile(appPath + "code.enc", appPath + "roundtrip.txt");


    // Read in the specified source file and write out an encoded target file.
    private static void EncodeFromFile(string sourceFile, string targetFile) 
        // Verify members.cs exists at the specified directory.
        if (!File.Exists(sourceFile))
            Console.Write("Unable to locate source file located at ");
            Console.WriteLine(sourceFile + ".");
            Console.Write("Please correct the path and run the ");
            Console.WriteLine("sample again.");

        // Retrieve the input and output file streams.
        using (FileStream inputFileStream =
            new FileStream(sourceFile, FileMode.Open, FileAccess.Read))
            using (FileStream outputFileStream =
                new FileStream(targetFile, FileMode.Create, FileAccess.Write))

                // Create a new ToBase64Transform object to convert to base 64.
                ToBase64Transform base64Transform = new ToBase64Transform();

                // Create a new byte array with the size of the output block size.
                byte[] outputBytes = new byte[base64Transform.OutputBlockSize];

                // Retrieve the file contents into a byte array.
                byte[] inputBytes = new byte[inputFileStream.Length];
                inputFileStream.Read(inputBytes, 0, inputBytes.Length);

                // Verify that multiple blocks can not be transformed.
                if (!base64Transform.CanTransformMultipleBlocks)
                    // Initializie the offset size.
                    int inputOffset = 0;

                    // Iterate through inputBytes transforming by blockSize.
                    int inputBlockSize = base64Transform.InputBlockSize;

                    while (inputBytes.Length - inputOffset > inputBlockSize)
                            inputBytes.Length - inputOffset,

                        inputOffset += base64Transform.InputBlockSize;

                    // Transform the final block of data.
                    outputBytes = base64Transform.TransformFinalBlock(
                        inputBytes.Length - inputOffset);

                    outputFileStream.Write(outputBytes, 0, outputBytes.Length);
                    Console.WriteLine("Created encoded file at " + targetFile);

                // Determine if the current transform can be reused.
                if (!base64Transform.CanReuseTransform)
                    // Free up any used resources.


        public static void DecodeFromFile(string inFileName, string outFileName)
            using (FromBase64Transform myTransform = new FromBase64Transform(FromBase64TransformMode.IgnoreWhiteSpaces))

                byte[] myOutputBytes = new byte[myTransform.OutputBlockSize];

                //Open the input and output files.
                using (FileStream myInputFile = new FileStream(inFileName, FileMode.Open, FileAccess.Read))
                    using (FileStream myOutputFile = new FileStream(outFileName, FileMode.Create, FileAccess.Write))

                        //Retrieve the file contents into a byte array. 
                        byte[] myInputBytes = new byte[myInputFile.Length];
                        myInputFile.Read(myInputBytes, 0, myInputBytes.Length);

                        //Transform the data in chunks the size of InputBlockSize. 
                        int i = 0;
                        while (myInputBytes.Length - i > 4/*myTransform.InputBlockSize*/)
                            int bytesWritten = myTransform.TransformBlock(myInputBytes, i, 4/*myTransform.InputBlockSize*/, myOutputBytes, 0);
                            i += 4/*myTransform.InputBlockSize*/;
                            myOutputFile.Write(myOutputBytes, 0, bytesWritten);

                        //Transform the final block of data.
                        myOutputBytes = myTransform.TransformFinalBlock(myInputBytes, i, myInputBytes.Length - i);
                        myOutputFile.Write(myOutputBytes, 0, myOutputBytes.Length);

                        //Free up any used resources.


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.