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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, 

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.



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

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, 1.1, 1.0