Convert.FromBase64String(String) 方法

参考

定义

命名空间:: System

程序集:: System.Runtime.Extensions.dll

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

将指定的字符串（它将二进制数据编码为 Base64 数字）转换为等效的 8 位无符号整数数组。

public:
 static cli::array <System::Byte> ^ FromBase64String(System::String ^ s);

public static byte[] FromBase64String (string s);

static member FromBase64String : string -> byte[]

Public Shared Function FromBase64String (s As String) As Byte()

参数

s: String

要转换的字符串。

Byte[]

与 s 等效的 8 位无符号整数数组。

例外

ArgumentNullException

s 上声明的默认值为 null。

FormatException

s 的长度（忽略空格）不是 0 或 4 的倍数。

或 -

s 的格式无效。 s 包含非 base 64 字符、两个以上的填充字符或者在填充字符中包含非空格字符。

示例

以下示例使用 ToBase64String(Byte[]) 此方法将字节数组转换为 UUencoded (base-64) 字符串，然后调用 FromBase64String(String) 该方法来还原原始字节数组。

using System;

public class Example
{
   public static void Main()
   {
       // Define a byte array.
       byte[] bytes = { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 };
       Console.WriteLine("The byte array: ");
       Console.WriteLine("   {0}\n", BitConverter.ToString(bytes));

       // Convert the array to a base 64 string.
       string s = Convert.ToBase64String(bytes);
       Console.WriteLine("The base 64 string:\n   {0}\n", s);

       // Restore the byte array.
       byte[] newBytes = Convert.FromBase64String(s);
       Console.WriteLine("The restored byte array: ");
       Console.WriteLine("   {0}\n", BitConverter.ToString(newBytes));
   }
}
// The example displays the following output:
//     The byte array:
//        02-04-06-08-0A-0C-0E-10-12-14
//
//     The base 64 string:
//        AgQGCAoMDhASFA==
//
//     The restored byte array:
//        02-04-06-08-0A-0C-0E-10-12-14

open System

// Define a byte array.
let bytes = [| 2uy; 4uy; 6uy; 8uy; 10uy; 12uy; 14uy; 16uy; 18uy; 20uy |]
printfn $"The byte array:\n   {BitConverter.ToString bytes}\n"

// Convert the array to a base 64 string.
let s = Convert.ToBase64String bytes
printfn $"The base 64 string:\n   {s}\n"

// Restore the byte array.
let newBytes = Convert.FromBase64String s
printfn $"The restored byte array:\n   {BitConverter.ToString newBytes}\n"

// The example displays the following output:
//     The byte array:
//        02-04-06-08-0A-0C-0E-10-12-14
//
//     The base 64 string:
//        AgQGCAoMDhASFA==
//
//     The restored byte array:
//        02-04-06-08-0A-0C-0E-10-12-14

Module Example
   Public Sub Main()
       ' Define a byte array.
       Dim bytes As Byte() = { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 }
       Console.WriteLine("The byte array: ")
       Console.WriteLine("   {0}", BitConverter.ToString(bytes))
       Console.WriteLine()
       
       ' Convert the array to a base 64 string.
       Dim s As String = Convert.ToBase64String(bytes)
       Console.WriteLine("The base 64 string:{1}   {0}{1}", 
                         s, vbCrLf)
       
       ' Restore the byte array.
       Dim newBytes As Byte() = Convert.FromBase64String(s)
       Console.WriteLine("The restored byte array: ")
       Console.WriteLine("   {0}", BitConverter.ToString(newBytes))
       Console.WriteLine()
   End Sub
End Module
' The example displays the following output:
'     The byte array:
'        02-04-06-08-0A-0C-0E-10-12-14
'     
'     The base 64 string:
'        AgQGCAoMDhASFA==
'     
'     The restored byte array:
'        02-04-06-08-0A-0C-0E-10-12-14

下面是一个更复杂的示例，用于创建 32 位整数的 20 元素数组。然后，该方法使用 BitConverter.GetBytes(Int32) 该方法将每个元素转换为字节数组，该数组通过调用 Array.Copy(Array, Int32, Array, Int32, Int32) 该方法存储在缓冲区中的相应位置。然后将此缓冲区传递给 ToBase64String(Byte[]) 方法，以创建 UUencoded (base-64) 字符串。然后，它会调用 FromBase64String(String) 该方法来解码 UUencoded 字符串，并调用 BitConverter.ToInt32 该方法将每组四个字节 (32 位整数的大小) 转换为整数。该示例的输出显示原始数组已成功还原。

using System;

public class Example
{
   public static void Main()
   {
      // Define an array of 20 elements and display it.
      int[] arr = new int[20];
      int value = 1;
      for (int ctr = 0; ctr <= arr.GetUpperBound(0); ctr++) {
         arr[ctr] = value;
         value = value * 2 + 1;
      }
      DisplayArray(arr);

      // Convert the array of integers to a byte array.
      byte[] bytes = new byte[arr.Length * 4];
      for (int ctr = 0; ctr < arr.Length; ctr++) {
         Array.Copy(BitConverter.GetBytes(arr[ctr]), 0,
                    bytes, ctr * 4, 4);
      }

      // Encode the byte array using Base64 encoding
      String base64 = Convert.ToBase64String(bytes);
      Console.WriteLine("The encoded string: ");
      for (int ctr = 0; ctr <= base64.Length / 50; ctr++)
         Console.WriteLine(base64.Substring(ctr * 50,
                                            ctr * 50 + 50 <= base64.Length
                                               ? 50 : base64.Length - ctr * 50));
      Console.WriteLine();

      // Convert the string back to a byte array.
      byte[] newBytes = Convert.FromBase64String(base64);

      // Convert the byte array back to an integer array.
      int[] newArr = new int[newBytes.Length/4];
      for (int ctr = 0; ctr < newBytes.Length / 4; ctr ++)
         newArr[ctr] = BitConverter.ToInt32(newBytes, ctr * 4);

      DisplayArray(newArr);
   }

   private static void DisplayArray(Array arr)
   {
      Console.WriteLine("The array:");
      Console.Write("{ ");
      for (int ctr = 0; ctr < arr.GetUpperBound(0); ctr++) {
         Console.Write("{0}, ", arr.GetValue(ctr));
         if ((ctr + 1) % 10 == 0)
            Console.Write("\n  ");
      }
      Console.WriteLine("{0} {1}", arr.GetValue(arr.GetUpperBound(0)), "}");
      Console.WriteLine();
   }
}
// The example displays the following output:
// The array:
// { 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023,
//   2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575 }
//
// The encoded string:
// AQAAAAMAAAAHAAAADwAAAB8AAAA/AAAAfwAAAP8AAAD/AQAA/w
// MAAP8HAAD/DwAA/x8AAP8/AAD/fwAA//8AAP//AQD//wMA//8H
//
// The array:
// { 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023,
//   2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575 }

open System

let displayArray (arr: 'a[]) =
    printfn "The array:"
    printf "{ "
    for i = 0 to arr.GetUpperBound(0) - 1 do
        printf $"{arr[i]}, "
        if (i + 1) % 10 = 0 then
            printf "\n  "
    printfn $"{arr[arr.GetUpperBound 0]} }}\n"

// Define an array of 20 elements and display it.
let arr = Array.zeroCreate<int> 20
let mutable value = 1
for i = 0 to arr.GetUpperBound 0 do
    arr[i] <- value
    value <- value * 2 + 1
displayArray arr

// Convert the array of integers to a byte array.
let bytes = Array.zeroCreate<byte> (arr.Length * 4)
for i = 0 to arr.Length - 1 do
    Array.Copy(BitConverter.GetBytes(arr[i]), 0, bytes, i * 4, 4)

// Encode the byte array using Base64 encoding
let base64 = Convert.ToBase64String bytes
printfn "The encoded string: "
printfn $"{base64}\n"

// Convert the string back to a byte array.
let newBytes = Convert.FromBase64String base64

// Convert the byte array back to an integer array.
let newArr = Array.zeroCreate<int> (newBytes.Length / 4)
for i = 0 to newBytes.Length / 4 - 1 do
    newArr[i] <- BitConverter.ToInt32(newBytes, i * 4)

displayArray newArr

// The example displays the following output:
// The array:
// { 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023,
//   2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575 }
//
// The encoded string:
// AQAAAAMAAAAHAAAADwAAAB8AAAA/AAAAfwAAAP8AAAD/AQAA/wMAAP8HAAD/DwAA/x8AAP8/AAD/fwAA//8AAP//AQD//wMA//8HAP//DwA=
//
// The array:
// { 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023,
//   2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575 }

Module Example
   Public Sub Main()
      ' Define an array of 20 elements and display it.
      Dim arr(19) As Integer 
      Dim value As Integer = 1
      For ctr As Integer = 0 To arr.GetUpperBound(0)
         arr(ctr) = value
         value = value * 2 + 1
      Next
      DisplayArray(arr)

      ' Convert the array of integers to a byte array.
      Dim bytes(arr.Length * 4 - 1) As Byte 
      For ctr As Integer = 0 To arr.Length - 1
         Array.Copy(BitConverter.GetBytes(arr(ctr)), 0, 
                    bytes, ctr * 4, 4)
      Next
         
      ' Encode the byte array using Base64 encoding
      Dim base64 As String = Convert.ToBase64String(bytes)
      Console.WriteLine("The encoded string: ")
      For ctr As Integer = 0 To base64.Length \ 50 - 1 
         Console.WriteLine(base64.Substring(ctr * 50, 
                                            If(ctr * 50 + 50 <= base64.Length, 
                                               50, base64.Length - ctr * 50)))
      Next
      Console.WriteLine()
      
      ' Convert the string back to a byte array.
      Dim newBytes() As Byte = Convert.FromBase64String(base64)

      ' Convert the byte array back to an integer array.
      Dim newArr(newBytes.Length\4 - 1) As Integer
      For ctr As Integer = 0 To newBytes.Length \ 4 - 1
         newArr(ctr) = BitConverter.ToInt32(newBytes, ctr * 4)
      Next   
      DisplayArray(newArr)
   End Sub

   Private Sub DisplayArray(arr As Array)
      Console.WriteLine("The array:")
      Console.Write("{ ")
      For ctr As Integer = 0 To arr.GetUpperBound(0) - 1
         Console.Write("{0}, ", arr.GetValue(ctr))
         If (ctr + 1) Mod 10 = 0 Then Console.Write("{0}  ", vbCrLf)
      Next
      Console.WriteLine("{0} {1}", arr.GetValue(arr.GetUpperBound(0)), "}")
      Console.WriteLine()
   End Sub
End Module
' The example displays the following output:
'     The array:
'     { 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023,
'       2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575 }
'     
'     The encoded string:
'     AQAAAAMAAAAHAAAADwAAAB8AAAA/AAAAfwAAAP8AAAD/AQAA/w
'     MAAP8HAAD/DwAA/x8AAP8/AAD/fwAA//8AAP//AQD//wMA//8H
'     
'     The array:
'     { 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023,
'       2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575 }

注解

s 由 base-64 数字、空格字符和尾随填充字符组成。从零开始的基数 64 位数字是大写字符“A”到“Z”，小写字符“a”到“z”，数字“0”到“9”，符号“+”和“/”。

空格字符及其 Unicode 名称和十六进制代码位是制表符 (字符制表符、U+0009) 、换行符 (行源、U+000A) 、回车 (回车、U+000D) 和空白 (空格、U+0020) 。任意数量的空白字符可以出现在其中 s ，因为所有空白字符将被忽略。

无值字符“=”用于尾随填充。结尾 s 可以包含零个、一个或两个填充字符。

重要

该方法 FromBase64String 旨在处理包含要解码的所有数据的单个字符串。若要从流解码 base-64 字符数据，请使用 System.Security.Cryptography.FromBase64Transform 该类。

适用于

通过

Convert.FromBase64String(String) 方法

定义

参数

返回

例外

示例

注解

适用于

另请参阅

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