UTF8Encoding.GetBytes Method (String, Int32, Int32, Byte[], Int32)


Encodes a set of characters from the specified String into the specified byte array.

Namespace:   System.Text
Assembly:  mscorlib (in mscorlib.dll)

public override int GetBytes(
	string s,
	int charIndex,
	int charCount,
	byte[] bytes,
	int byteIndex


Type: System.String

The String containing the set of characters to encode.

Type: System.Int32

The index of the first character to encode.

Type: System.Int32

The number of characters to encode.

Type: System.Byte[]

The byte array to contain the resulting sequence of bytes.

Type: System.Int32

The index at which to start writing the resulting sequence of bytes.

Return Value

Type: System.Int32

The actual number of bytes written into bytes.

Exception Condition

s is null.


bytes is null.


charIndex or charCount or byteIndex is less than zero.


charIndex and charCount do not denote a valid range in chars.


byteIndex is not a valid index in bytes.


Error detection is enabled, and s contains an invalid sequence of characters.


bytes does not have enough capacity from byteIndex to the end of the array to accommodate the resulting bytes.


A fallback occurred (see Character Encoding in the .NET Framework for complete explanation)


EncoderFallback is set to EncoderExceptionFallback.

To calculate the exact array size required by GetBytes to store the resulting bytes, you call the GetByteCount method. To calculate the maximum array size, you call the GetMaxByteCount method. The GetByteCount method generally allocates less memory, while the GetMaxByteCount method generally executes faster.

With error detection, an invalid sequence causes this method to throw an ArgumentException exception. Without error detection, invalid sequences are ignored, and no exception is thrown.

Data to be converted, such as data read from a stream, might be available only in sequential blocks. In this case, or if the amount of data is so large that it needs to be divided into smaller blocks, use the Decoder or the Encoder provided by the GetDecoder method or the GetEncoder method, respectively.

To ensure that the encoded bytes are decoded properly when they are saved as a file or as a stream, you can prefix a stream of encoded bytes with a preamble. Inserting the preamble at the beginning of a byte stream (such as at the beginning of a series of bytes to be written to a file) is the developer's responsibility. The GetBytes method does not prepend a preamble to the beginning of a sequence of encoded bytes.

The following example uses the GetBytes method to encode a range of elements from a Unicode character array and store the encoded bytes in a range of elements in a byte array.

using System;
using System.Text;

class UTF8EncodingExample {
    public static void Main() {
        Byte[] bytes;
        // Unicode characters.
        Char[] chars = new Char[] {
            '\u0023', // #
            '\u0025', // %
            '\u03a0', // Pi
            '\u03a3'  // Sigma

        UTF8Encoding utf8 = new UTF8Encoding();

        int byteCount = utf8.GetByteCount(chars, 1, 2);
        bytes = new Byte[byteCount];
        int bytesEncodedCount = utf8.GetBytes(chars, 1, 2, bytes, 0);

            "{0} bytes used to encode characters.", bytesEncodedCount

        Console.Write("Encoded bytes: ");
        foreach (Byte b in bytes) {
            Console.Write("[{0}]", b);

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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