Converting string to byte array in C

Question

I m converting something from VB into C   Having a problem with the syntax of this statement   if   searchResult Properties  user   Count  gt  0         profile User   System Text Encoding UTF8 GetString searchResult Properties  user   0        I then see the following errors      Argument 1  cannot convert from  object  to  byte         The best overloaded method match for    System Text Encoding GetString byte     has some invalid arguments   I tried to fix the code based on this post  but still no success  string User   Encoding UTF8 GetString  user   0     Any suggestions

User · Answer

You could use MemoryMarshal API to perform very fast and efficient conversion. String will implicitly be cast to ReadOnlySpan<byte>, as MemoryMarshal.Cast accepts either Span<byte> or ReadOnlySpan<byte> as an input parameter.

public static class StringExtensions
{
    public static byte[] ToByteArray(this string s) => s.ToByteSpan().ToArray(); //  heap allocation, use only when you cannot operate on spans
    public static ReadOnlySpan<byte> ToByteSpan(this string s) => MemoryMarshal.Cast<char, byte>(s);
}

Following benchmark shows the difference:

Input: "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s,"

|                       Method |       Mean |     Error |    StdDev |  Gen 0 | Gen 1 | Gen 2 | Allocated |
|----------------------------- |-----------:|----------:|----------:|-------:|------:|------:|----------:|
| UsingEncodingUnicodeGetBytes | 160.042 ns | 3.2864 ns | 6.4099 ns | 0.0780 |     - |     - |     328 B |
| UsingMemoryMarshalAndToArray |  31.977 ns | 0.7177 ns | 1.5753 ns | 0.0781 |     - |     - |     328 B |
|           UsingMemoryMarshal |   1.027 ns | 0.0565 ns | 0.1630 ns |      - |     - |     - |         - |

User · Answer

var result   System Text Encoding Unicode GetBytes text

User · Answer

static byte   GetBytes string str         byte   bytes   new byte str Length   sizeof char         System Buffer BlockCopy str ToCharArray    0  bytes  0  bytes Length        return bytes     static string GetString byte   bytes         char   chars   new char bytes Length   sizeof char         System Buffer BlockCopy bytes  0  chars  0  bytes Length        return new string chars

User · Answer

The following approach will work only if the chars are 1 byte   Default unicode will not work since it is 2 bytes   public static byte   ToByteArray string value                    char   charArr   value ToCharArray        byte   bytes   new byte charArr Length       for  int i   0  i  lt  charArr Length  i                  byte current   Convert ToByte charArr i            bytes i    current             return bytes      Keeping it simple

User · Answer

use this   byte   myByte  System Text ASCIIEncoding Default GetBytes myString

User · Answer

Also you can use an Extension Method to add a method to the string type as below   static class Helper      public static byte   ToByteArray this string str             return System Text Encoding ASCII GetBytes str            And use it like below   string foo    bla bla   byte   result   foo ToByteArray

User · Answer

A refinement to JustinStolle s edit  Eran Yogev s use of BlockCopy    The proposed solution is indeed faster than using Encoding  Problem is that it doesn t work for encoding byte arrays of uneven length  As given  it raises an out-of-bound exception  Increasing the length by 1 leaves a trailing byte when decoding from string   For me  the need came when I wanted to encode from DataTable to JSON  I was looking for a way to encode binary fields into strings and decode from string back to byte     I therefore created two classes - one that wraps the above solution  when encoding from strings it s fine  because the lengths are always even   and another that handles byte   encoding   I solved the uneven length problem by adding a single character that tells me if the original length of the binary array was odd   1   or even   0    As follows   public static class StringEncoder       static byte   EncodeToBytes string str                byte   bytes   new byte str Length   sizeof char            System Buffer BlockCopy str ToCharArray    0  bytes  0  bytes Length           return bytes            static string DecodeToString byte   bytes                char   chars   new char bytes Length   sizeof char            System Buffer BlockCopy bytes  0  chars  0  bytes Length           return new string chars            public static class BytesEncoder       public static string EncodeToString byte   bytes                bool even    bytes Length   2    0           char   chars   new char 1   bytes Length   sizeof char     even   0   1            chars 0     even    0     1            System Buffer BlockCopy bytes  0  chars  2  bytes Length            return new string chars             public static byte   DecodeToBytes string str                bool even   str 0      0           byte   bytes   new byte  str Length - 1    sizeof char     even   0   -1            char   chars   str ToCharArray            System Buffer BlockCopy chars  2  bytes  0  bytes Length            return bytes

User · Answer

This work for me  after that I could convert put my picture in a bytea field in my database   using  MemoryStream s   new MemoryStream DirEntry Properties  thumbnailphoto   Value as byte           return s ToArray

User · Answer

If the result of   searchResult Properties    user      0     is a string   if     searchResult Properties    user    Count  gt  0           profile User   System Text Encoding UTF8 GetString   searchResult Properties    user      0   ToCharArray    Select   character   gt    byte   character   ToArray            The key point being that converting a string to a byte    can be done using LINQ    ToCharArray    Select   character   gt    byte   character   ToArray        And the inverse    Select   character   gt    char   character   ToArray

User · Answer

This question has been answered sufficiently many times  but with C  7 2 and the introduction of the Span type  there is a faster way to do this in unsafe code   public static class StringSupport       private static readonly int  charSize   sizeof char        public static unsafe byte   GetBytes string str                if  str    null  throw new ArgumentNullException nameof str            if  str Length    0  return new byte 0            fixed  char  p   str                        return new Span lt byte gt  p  str Length    charSize  ToArray                         public static unsafe string GetString byte   bytes                if  bytes    null  throw new ArgumentNullException nameof bytes            if  bytes Length    charSize    0  throw new ArgumentException   Invalid  nameof bytes   length            if  bytes Length    0  return string Empty           fixed  byte  p   bytes                        return new string new Span lt char gt  p  bytes Length    charSize                        Keep in mind that the bytes represent a UTF-16 encoded string  called  Unicode  in C  land    Some quick benchmarking shows that the above methods are roughly 5x faster than their Encoding Unicode GetBytes      GetString      implementations for medium sized strings  30-50 chars   and even faster for larger strings  These methods also seem to be faster than using pointers with Marshal Copy     or Buffer MemoryCopy

User · Answer

Building off Ali s answer  I would recommend an extension method that allows you to optionally pass in the encoding you want to use   using System Text  public static class StringExtensions            lt summary gt          Creates a byte array from the string  using the          System Text Encoding Default encoding unless another is specified           lt  summary gt      public static byte   ToByteArray this string str  Encoding encoding   Encoding Default                return encoding GetBytes str             And use it like below   string foo    bla bla       default encoding byte   default   foo ToByteArray        custom encoding byte   unicode   foo ToByteArray Encoding Unicode

User · Answer

This has been answered quite a lot  but for me  the only working method is this one      public static byte   StringToByteArray string str                byte   array   Convert FromBase64String str           return array

User · Answer

Does anyone see any reason why not to do this   mystring Select Convert ToByte  ToArray

User · Answer

This what worked for me byte   bytes   Convert FromBase64String textString    And in reverse  string str   Convert ToBase64String bytes

User · Answer

If you already have a byte array then you will need to know what type of encoding was used to make it into that byte array   For example  if the byte array was created like this   byte   bytes   Encoding ASCII GetBytes someString     You will need to turn it back into a string like this   string someString   Encoding ASCII GetString bytes     If you can find in the code you inherited  the encoding used to create the byte array then you should be set

User · Answer

First of all  add the System Text namespace  using System Text    Then use this code  string input    some text    byte   array   Encoding ASCII GetBytes input     Hope to fix it

User · Answer

Encoding Default should not be used     Randall s answer uses Encoding Default  however Microsoft raises a warning against it   Different computers can use different encodings as the default  and the default encoding can change on a single computer  If you use the Default encoding to encode and decode data streamed between computers or retrieved at different times on the same computer  it may translate that data incorrectly  In addition  the encoding returned by the Default property uses best-fit fallback to map unsupported characters to characters supported by the code page  For these reasons  using the default encoding is not recommended  To ensure that encoded bytes are decoded properly  you should use a Unicode encoding  such as UTF8Encoding or UnicodeEncoding  You could also use a higher-level protocol to ensure that the same format is used for encoding and decoding   To check what the default encoding is  use Encoding Default WindowsCodePage  1250 in my case - and sadly  there is no predefined class of CP1250 encoding  but the object could be retrieved as Encoding GetEncoding 1250       UTF-8 encoding should be used instead    Encoding ASCII is 7bit  so it doesn t work either  in my case  byte   pass   Encoding ASCII GetBytes  quot   ar  e quot    Console WriteLine Encoding ASCII GetString pass        ar e  Following Microsoft s recommendation  var utf8   new UTF8Encoding    byte   pass   utf8 GetBytes  quot   ar  e quot    Console WriteLine utf8 GetString pass         ar  e  Encoding UTF8 recommended by others is an instance uf UTF-8 encoding and can be also used directly or as var utf8   Encoding UTF8 as UTF8Encoding      but it is not used always Default encoding is misleading   NET uses UTF-8 everywhere  including strings hardcoded in the source code   but Windows actually uses 2 other non-UTF8 non-standard defaults  ANSI codepage  for GUI apps before  NET  and OEM codepage  aka DOS standard   These differs from country to country  for instance  Windows Czech edition uses CP1250 and CP852  and are oftentimes hardcoded in windows API libraries  So if you just set UTF-8 to console by chcp 65001  as  NET implicitly does and pretends it is the default  and run some localized command  like ping   it works in English version  but you get tofu text in Czech Republic  Let me share my real world experience  I created WinForms application customizing git scripts for teachers  The output is obtained on the background anynchronously by a process described by Microsoft as  bold text added by me    The word  quot shell quot  in this context  UseShellExecute  refers to a graphical shell  ANSI CP   similar to the Windows shell  rather than command shells  for example  bash or sh   OEM CP  and lets users launch graphical applications or open documents  with messed output in non-US environment    So effectively GUI defaults to UTF-8  process defaults to CP1250 and console defaults to 852  So the output is in 852 interpreted as UTF-8 interpreted as CP1250  I got tofu text from which I could not deduce the original codepage due to the double conversion  I was pulling my hair for a week to figure out to explicitly set UTF-8 for process script and convert the output from CP1250 to UTF-8 in the main thread  Now it works here in the Eastern Europe  but Western Europe Windows uses 1252  ANSI CP is not determined easily as many commands like systeminfo are also localized and other methods differs from version to version  in such environment displaying national characters reliably is almost unfeasible  So until the half of 21st century  please DO NOT use any  quot Default Codepage quot  and set it explicitly  to UTF-8 if possible

[c#] Converting string to byte array in C#

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