Convert.FromBase64String-Methode
Konvertiert die angegebene String, die Binärdaten als Base-64-Ziffern codiert, in ein entsprechendes Array von 8-Bit-Ganzzahlen ohne Vorzeichen.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared Function FromBase64String ( _
s As String _
) As Byte()
'Usage
Dim s As String
Dim returnValue As Byte()
returnValue = Convert.FromBase64String(s)
public static byte[] FromBase64String (
string s
)
public:
static array<unsigned char>^ FromBase64String (
String^ s
)
public static byte[] FromBase64String (
String s
)
public static function FromBase64String (
s : String
) : byte[]
Parameter
- s
Ein String.
Rückgabewert
Ein Array von 8-Bit-Ganzzahlen ohne Vorzeichen, das s entspricht.
Ausnahmen
| Ausnahmetyp | Bedingung |
|---|---|
s ist NULL (Nothing in Visual Basic). |
|
Die Länge von s ist ohne Leerraumzeichen nicht 0 (null) und kein Vielfaches von 4. – oder – Das Format von s ist ungültig. s enthält ein Nicht-Base-64-Zeichen, mehr als zwei Füllzeichen oder ein Füllzeichen, das kein Leerraumzeichen ist. |
Hinweise
s besteht aus Base-64-Ziffern, Leerraumzeichen und nachfolgenden Füllzeichen. Die Base-64-Ziffern sind in von 0 (null) aufsteigender Reihenfolge die Großbuchstaben 'A' bis 'Z', die Kleinbuchstaben 'a' bis 'z', die Ziffern '0' bis '9' und die Zeichen '+' und '/'.
Zu den Leerraumzeichen (mit Unicode-Namen und hexadezimalem Codepunkt) zählen die folgenden: Tabstoppzeichen (CHARACTER TABULATION, U+0009), Zeilenumbruch (LINE FEED, U+000A), Wagenrücklauf (CARRIAGE RETURN, U+000D) und Leerzeichen (SPACE, U+0020). In s kann eine beliebige Anzahl von Leerraumzeichen enthalten sein, da diese ignoriert werden.
Das wertfreie Zeichen '=' wird für nachfolgende Füllzeichen verwendet. Das Ende von s kann aus keinem, einem oder zwei Füllzeichen bestehen.
Beispiel
Im folgenden Codebeispiel wird die Verwendung der FromBase64String-Methode zum Decodieren von UUencode-Daten (Base-64) und zum Speichern dieser Daten als binäre Ausgabe veranschaulicht.
Public Sub DecodeWithString()
Dim inFile As System.IO.StreamReader
Dim base64String As String
Try
Dim base64CharArray() As Char
inFile = New System.IO.StreamReader(inputFileName, _
System.Text.Encoding.ASCII)
base64CharArray = New Char(inFile.BaseStream.Length) {}
inFile.Read(base64CharArray, 0, inFile.BaseStream.Length)
base64String = New String(base64CharArray, _
0, _
base64CharArray.Length - 1)
Catch exp As System.Exception
' Error creating stream or reading from it.
System.Console.WriteLine("{0}", exp.Message)
Return
End Try
' Convert the Base64 UUEncoded input into binary output.
Dim binaryData() As Byte
Try
binaryData = System.Convert.FromBase64String(base64String)
Catch exp As System.ArgumentNullException
System.Console.WriteLine("Base 64 string is null.")
Return
Catch exp As System.FormatException
System.Console.WriteLine("Base 64 length is not 4 or is " + _
"not an even multiple of 4.")
Return
End Try
'Write out the decoded data.
Dim outFile As System.IO.FileStream
Try
outFile = New System.IO.FileStream(outputFileName, _
System.IO.FileMode.Create, _
System.IO.FileAccess.Write)
outFile.Write(binaryData, 0, binaryData.Length - 1)
outFile.Close()
Catch exp As System.Exception
' Error creating stream or writing to it.
System.Console.WriteLine("{0}", exp.Message)
End Try
End Sub
public void DecodeWithString() {
System.IO.StreamReader inFile;
string base64String;
try {
char[] base64CharArray;
inFile = new System.IO.StreamReader(inputFileName,
System.Text.Encoding.ASCII);
base64CharArray = new char[inFile.BaseStream.Length];
inFile.Read(base64CharArray, 0, (int)inFile.BaseStream.Length);
base64String = new string(base64CharArray);
}
catch (System.Exception exp) {
// Error creating stream or reading from it.
System.Console.WriteLine("{0}", exp.Message);
return;
}
// Convert the Base64 UUEncoded input into binary output.
byte[] binaryData;
try {
binaryData =
System.Convert.FromBase64String(base64String);
}
catch (System.ArgumentNullException) {
System.Console.WriteLine("Base 64 string is null.");
return;
}
catch (System.FormatException) {
System.Console.WriteLine("Base 64 string length is not " +
"4 or is not an even multiple of 4." );
return;
}
// Write out the decoded data.
System.IO.FileStream outFile;
try {
outFile = new System.IO.FileStream(outputFileName,
System.IO.FileMode.Create,
System.IO.FileAccess.Write);
outFile.Write(binaryData, 0, binaryData.Length);
outFile.Close();
}
catch (System.Exception exp) {
// Error creating stream or writing to it.
System.Console.WriteLine("{0}", exp.Message);
}
}
public:
void DecodeWithString()
{
StreamReader^ inFile;
String^ base64String;
try
{
array<Char>^base64CharArray;
inFile = gcnew StreamReader( inputFileName,
Text::Encoding::ASCII );
base64CharArray = gcnew array<Char>((int)(inFile->BaseStream->Length));
inFile->Read( base64CharArray, 0, (int)inFile->BaseStream->Length );
base64String = gcnew String( base64CharArray );
}
catch ( Exception^ exp )
{
// Error creating stream or reading from it.
Console::WriteLine( "{0}", exp->Message );
return;
}
// Convert the Base64 UUEncoded input into binary output.
array<Byte>^binaryData;
try
{
binaryData = Convert::FromBase64String( base64String );
}
catch ( ArgumentNullException^ )
{
Console::WriteLine( "Base 64 String^ is null." );
return;
}
catch ( FormatException^ )
{
Console::WriteLine( "Base 64 String^ length is not " +
"4 or is not an even multiple of 4." );
return;
}
// Write out the decoded data.
FileStream^ outFile;
try
{
outFile = gcnew FileStream( outputFileName,
FileMode::Create,
FileAccess::Write );
outFile->Write( binaryData, 0, binaryData->Length );
outFile->Close();
}
catch ( Exception^ exp )
{
// Error creating stream or writing to it.
Console::WriteLine( "{0}", exp->Message );
}
}
public void DecodeWithString()
{
System.IO.StreamReader inFile;
String base64String;
try {
char base64CharArray[];
inFile = new System.IO.StreamReader(inputFileName,
System.Text.Encoding.get_ASCII());
base64CharArray = new char[
(int)inFile.get_BaseStream().get_Length()];
inFile.Read(base64CharArray,0,
(int)(inFile.get_BaseStream().get_Length()));
base64String = new String(base64CharArray);
}
catch (System.Exception exp) {
// Error creating stream or reading from it.
System.Console.WriteLine("{0}", exp.get_Message());
return;
}
// Convert the Base64 UUEncoded input into binary output.
ubyte binaryData[];
try {
binaryData = System.Convert.FromBase64String(base64String);
}
catch (System.ArgumentNullException exp) {
System.Console.WriteLine("Base 64 string is null.");
return;
}
catch (System.FormatException exp) {
System.Console.WriteLine(("Base 64 string length is not "
+ "4 or is not an even multiple of 4."));
return;
}
// Write out the decoded data.
System.IO.FileStream outFile;
try {
outFile = new System.IO.FileStream(outputFileName,
System.IO.FileMode.Create, System.IO.FileAccess.Write);
outFile.Write(binaryData, 0, binaryData.length);
outFile.Close();
}
catch (System.Exception exp) {
// Error creating stream or writing to it.
System.Console.WriteLine("{0}", exp.get_Message());
}
} //DecodeWithString
Im folgenden Codebeispiel werden die ToBase64String-Methode und die FromBase64String-Methode dargestellt. Die Eingabe wird in Gruppen von jeweils 3 Bytes (24 Bits) unterteilt. Folglich besteht jede Gruppe aus vier 6-Bit-Zahlen, wobei jede Zahl im Bereich von 0 (null) bis 63 liegt. In diesem Beispiel gibt es 85 3-Byte-Gruppen mit einem Rest von einem Byte. Die erste Gruppe besteht aus den Hexadezimalwerten 00, 01 und 02, die vier 6-Bit-Werte gleich den Dezimalwerten 0, 0, 4 und 2 ergeben. Diese vier Werte entsprechen den Base-64-Ziffern "A", "A", "E" und "C" am Anfang der Ausgabe.
Wenn eine Aufteilung in 3-Byte-Gruppen ohne Rest nicht möglich ist, werden die verbleibenden Bytes mit Nullen zu einer vollständigen Gruppe aufgefüllt. In diesem Beispiel ist der Hexadezimalwert des letzten Bytes FF. Die ersten 6 Bits sind gleich dem Dezimalwert 63, der der Base-64-Ziffer "/" am Ende der Ausgabe entspricht, und die nächsten 2 Bits sind mit Nullen aufgefüllt, sodass sie den Dezimalwert 48 ergeben, der der Base-64-Ziffer "w" entspricht. Die letzten zwei 6-Bit-Werte werden aufgefüllt und entsprechen dem wertfreien Füllzeichen "=".
' This example demonstrates the Convert.ToBase64String() and
' Convert.FromBase64String() methods
Imports System
Class Sample
Public Shared Sub Main()
Dim inArray(255) As Byte
Dim outArray(255) As Byte
Dim s2 As String
Dim s3 As String
Dim step1 As String = "1) The input is a byte array (inArray) of arbitrary data."
Dim step2 As String = "2) Convert a subarray of the input data array to a base 64 string."
Dim step3 As String = "3) Convert the entire input data array to a base 64 string."
Dim step4 As String = "4) The two methods in steps 2 and 3 produce the same result?: {0}"
Dim step5 As String = "5) Convert the base 64 string to an output byte array (outArray)."
Dim step6 As String = "6) The input and output arrays, inArray and outArray, are equal?: {0}"
Dim x As Integer
Dim nl As String = Environment.NewLine
Dim ruler1a As String = " 1 2 3 4"
Dim ruler2a As String = "1234567890123456789012345678901234567890"
Dim ruler3a As String = "----+----+----+----+----+----+----+----+"
Dim ruler1b As String = " 5 6 7 "
Dim ruler2b As String = "123456789012345678901234567890123456"
Dim ruler3b As String = "----+----+----+----+----+----+----+-"
Dim ruler As String = [String].Concat(ruler1a, ruler1b, nl, ruler2a, ruler2b, nl, ruler3a, ruler3b, nl)
' 1) Display an arbitrary array of input data (inArray). The data could be
' derived from user input, a file, an algorithm, etc.
Console.WriteLine(step1)
Console.WriteLine()
For x = 0 To inArray.Length - 1
inArray(x) = CByte(x)
Console.Write("{0:X2} ", inArray(x))
If (x + 1) Mod 20 = 0 Then
Console.WriteLine()
End If
Next x
Console.Write("{0}{0}", nl)
' 2) Convert a subarray of the input data to a base64 string. In this case,
' the subarray is the entire input data array. New lines (CRLF) are inserted.
Console.WriteLine(step2)
s2 = Convert.ToBase64String(inArray, 0, inArray.Length, _
Base64FormattingOptions.InsertLineBreaks)
Console.WriteLine("{0}{1}{2}{3}", nl, ruler, s2, nl)
' 3) Convert the input data to a base64 string. In this case, the entire
' input data array is converted by default. New lines (CRLF) are inserted.
Console.WriteLine(step3)
s3 = Convert.ToBase64String(inArray, Base64FormattingOptions.InsertLineBreaks)
' 4) Test whether the methods in steps 2 and 3 produce the same result.
Console.WriteLine(step4, s2.Equals(s3))
' 5) Convert the base 64 string to an output array (outArray).
Console.WriteLine(step5)
outArray = Convert.FromBase64String(s2)
' 6) Is outArray equal to inArray?
Console.WriteLine(step6, ArraysAreEqual(inArray, outArray))
End Sub 'Main
Public Shared Function ArraysAreEqual(a1() As Byte, a2() As Byte) As Boolean
If a1.Length <> a2.Length Then
Return False
End If
Dim i As Integer
For i = 0 To a1.Length - 1
If a1(i) <> a2(i) Then
Return False
End If
Next i
Return True
End Function 'ArraysAreEqual
End Class 'Sample
'
'This example produces the following results:
'
'1) The input is a byte array (inArray) of arbitrary data.
'
'00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13
'14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27
'28 29 2A 2B 2C 2D 2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B
'3C 3D 3E 3F 40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
'50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F 60 61 62 63
'64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72 73 74 75 76 77
'78 79 7A 7B 7C 7D 7E 7F 80 81 82 83 84 85 86 87 88 89 8A 8B
'8C 8D 8E 8F 90 91 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F
'A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF B0 B1 B2 B3
'B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF C0 C1 C2 C3 C4 C5 C6 C7
'C8 C9 CA CB CC CD CE CF D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 DA DB
'DC DD DE DF E0 E1 E2 E3 E4 E5 E6 E7 E8 E9 EA EB EC ED EE EF
'F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FB FC FD FE FF
'
'2) Convert a subarray of the input data array to a base 64 string.
'
' 1 2 3 4 5 6 7
'1234567890123456789012345678901234567890123456789012345678901234567890123456
'----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+-
'AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8gISIjJCUmJygpKissLS4vMDEyMzQ1Njc4
'OTo7PD0+P0BBQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWltcXV5fYGFiY2RlZmdoaWprbG1ub3Bx
'cnN0dXZ3eHl6e3x9fn+AgYKDhIWGh4iJiouMjY6PkJGSk5SVlpeYmZqbnJ2en6ChoqOkpaanqKmq
'q6ytrq+wsbKztLW2t7i5uru8vb6/wMHCw8TFxsfIycrLzM3Oz9DR0tPU1dbX2Nna29zd3t/g4eLj
'5OXm5+jp6uvs7e7v8PHy8/T19vf4+fr7/P3+/w==
'
'3) Convert the entire input data array to a base 64 string.
'4) The two methods in steps 2 and 3 produce the same result?: True
'5) Convert the base 64 string to an output byte array (outArray).
'6) The input and output arrays, inArray and outArray, are equal?: True
'
// This example demonstrates the Convert.ToBase64String() and
// Convert.FromBase64String() methods
using System;
class Sample
{
public static void Main()
{
byte[] inArray = new byte[256];
byte[] outArray = new byte[256];
string s2;
string s3;
string step1 = "1) The input is a byte array (inArray) of arbitrary data.";
string step2 = "2) Convert a subarray of the input data array to a base 64 string.";
string step3 = "3) Convert the entire input data array to a base 64 string.";
string step4 = "4) The two methods in steps 2 and 3 produce the same result?: {0}";
string step5 = "5) Convert the base 64 string to an output byte array (outArray).";
string step6 = "6) The input and output arrays, inArray and outArray, are equal?: {0}";
int x;
string nl = Environment.NewLine;
string ruler1a = " 1 2 3 4";
string ruler2a = "1234567890123456789012345678901234567890";
string ruler3a = "----+----+----+----+----+----+----+----+";
string ruler1b = " 5 6 7 ";
string ruler2b = "123456789012345678901234567890123456";
string ruler3b = "----+----+----+----+----+----+----+-";
string ruler = String.Concat(ruler1a, ruler1b, nl,
ruler2a, ruler2b, nl,
ruler3a, ruler3b, nl);
// 1) Display an arbitrary array of input data (inArray). The data could be
// derived from user input, a file, an algorithm, etc.
Console.WriteLine(step1);
Console.WriteLine();
for (x = 0; x < inArray.Length; x++)
{
inArray[x] = (byte)x;
Console.Write("{0:X2} ", inArray[x]);
if (((x+1)%20) == 0) Console.WriteLine();
}
Console.Write("{0}{0}", nl);
// 2) Convert a subarray of the input data to a base64 string. In this case,
// the subarray is the entire input data array. New lines (CRLF) are inserted.
Console.WriteLine(step2);
s2 = Convert.ToBase64String(inArray, 0, inArray.Length,
Base64FormattingOptions.InsertLineBreaks);
Console.WriteLine("{0}{1}{2}{3}", nl, ruler, s2, nl);
// 3) Convert the input data to a base64 string. In this case, the entire
// input data array is converted by default. New lines (CRLF) are inserted.
Console.WriteLine(step3);
s3 = Convert.ToBase64String(inArray, Base64FormattingOptions.InsertLineBreaks);
// 4) Test whether the methods in steps 2 and 3 produce the same result.
Console.WriteLine(step4, s2.Equals(s3));
// 5) Convert the base 64 string to an output array (outArray).
Console.WriteLine(step5);
outArray = Convert.FromBase64String(s2);
// 6) Is outArray equal to inArray?
Console.WriteLine(step6, ArraysAreEqual(inArray, outArray));
}
public static bool ArraysAreEqual(byte[] a1, byte[] a2)
{
if (a1.Length != a2.Length) return false;
for (int i = 0; i < a1.Length; i++)
if (a1[i] != a2[i]) return false;
return true;
}
}
/*
This example produces the following results:
1) The input is a byte array (inArray) of arbitrary data.
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13
14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27
28 29 2A 2B 2C 2D 2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B
3C 3D 3E 3F 40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F 60 61 62 63
64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72 73 74 75 76 77
78 79 7A 7B 7C 7D 7E 7F 80 81 82 83 84 85 86 87 88 89 8A 8B
8C 8D 8E 8F 90 91 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F
A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF B0 B1 B2 B3
B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF C0 C1 C2 C3 C4 C5 C6 C7
C8 C9 CA CB CC CD CE CF D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 DA DB
DC DD DE DF E0 E1 E2 E3 E4 E5 E6 E7 E8 E9 EA EB EC ED EE EF
F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FB FC FD FE FF
2) Convert a subarray of the input data array to a base 64 string.
1 2 3 4 5 6 7
1234567890123456789012345678901234567890123456789012345678901234567890123456
----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+-
AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8gISIjJCUmJygpKissLS4vMDEyMzQ1Njc4
OTo7PD0+P0BBQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWltcXV5fYGFiY2RlZmdoaWprbG1ub3Bx
cnN0dXZ3eHl6e3x9fn+AgYKDhIWGh4iJiouMjY6PkJGSk5SVlpeYmZqbnJ2en6ChoqOkpaanqKmq
q6ytrq+wsbKztLW2t7i5uru8vb6/wMHCw8TFxsfIycrLzM3Oz9DR0tPU1dbX2Nna29zd3t/g4eLj
5OXm5+jp6uvs7e7v8PHy8/T19vf4+fr7/P3+/w==
3) Convert the entire input data array to a base 64 string.
4) The two methods in steps 2 and 3 produce the same result?: True
5) Convert the base 64 string to an output byte array (outArray).
6) The input and output arrays, inArray and outArray, are equal?: True
*/
Plattformen
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Mobile für Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
.NET Compact Framework
Unterstützt in: 2.0, 1.0