Converting string to byte array in C#

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.

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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!

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Encoding.Default should not be used...

Some answers use 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 [i.e. the encoding is totally screwed up, so you can't reencode it back] 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/UTF-16LE encoding should be used instead...

Encoding.ASCII in the most scoring answer is 7bit, so it doesn't work either, in my case:

byte[] pass = Encoding.ASCII.GetBytes("šarže");
Console.WriteLine(Encoding.ASCII.GetString(pass)); // ?ar?e

Following Microsoft's recommendation:

var utf8 = new UTF8Encoding();
byte[] pass = utf8.GetBytes("šarže");
Console.WriteLine(utf8.GetString(pass)); // šarže

Encoding.UTF8 recommended by others is an instance of UTF-8 encoding and can be also used directly or as

var utf8 = Encoding.UTF8 as UTF8Encoding;

Encoding.Unicode is popular for string representation in memory, because it uses fixed 2 bytes per char, so one can jump to n-th character in constant time at cost of more memory usage: it is UTF-16LE. In MSVC# The *.cs files are in UTF-8 BOM by default and string constants in them converted to UTF-16LE at compile time (see @OwnagelsMagic comment), but it is NOT defined as default: many classes like StreamWriter uses UTF-8 as default.

...but it is not used always

Default encoding is misleading: .NET uses UTF-8 everywhere (including strings hardcoded in the source code) and UTF-16LE (Encoding.Unicode) to store strings in memory, but Windows actually uses 2 other non-UTF8 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 "shell" 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 "Default Codepage" and set it explicitly (to UTF-8 or UTF-16LE if possible).

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var result = System.Text.Encoding.Unicode.GetBytes(text);

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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();

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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);
}

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This what worked for me

byte[] bytes = Convert.FromBase64String(textString);

And in reverse:

string str = Convert.ToBase64String(bytes);

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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
{
    /// <summary>
    /// Creates a byte array from the string, using the 
    /// System.Text.Encoding.Default encoding unless another is specified.
    /// </summary>
    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);

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use this

byte[] myByte= System.Text.ASCIIEncoding.Default.GetBytes(myString);

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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 < charArr.Length; i++)
    {
        byte current = Convert.ToByte(charArr[i]);
        bytes[i] = current;
    }

    return bytes;
}

Keeping it simple

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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 |      - |     - |     - |         - |

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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;
    }
}

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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<byte>(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<char>(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(...).

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Does anyone see any reason why not to do this?

mystring.Select(Convert.ToByte).ToArray()

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If the result of, 'searchResult.Properties [ "user" ] [ 0 ]', is a string:

if ( ( searchResult.Properties [ "user" ].Count > 0 ) ) {

   profile.User = System.Text.Encoding.UTF8.GetString ( searchResult.Properties [ "user" ] [ 0 ].ToCharArray ().Select ( character => ( byte ) character ).ToArray () );

}

The key point being that converting a string to a byte [] can be done using LINQ:

.ToCharArray ().Select ( character => ( byte ) character ).ToArray () )

And the inverse:

.Select ( character => ( char ) character ).ToArray () )

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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();
}

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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;
    }

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Thank you Pawel Maga

your contribution can be completed like this:

    public static byte[] ToByteArray(this string s) => s.ToByteSpan().ToArray();
    public static string FromByteArray(this byte[] bytes) => ToCharSpan(new ReadOnlySpan<byte>(bytes)).ToString();
    public static ReadOnlySpan<byte> ToByteSpan(this string str) => MemoryMarshal.Cast<char, byte>(str);
    public static ReadOnlySpan<char> ToCharSpan(this ReadOnlySpan<byte> bytes) => MemoryMarshal.Cast<byte, char>(bytes);

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