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UTF7Encoding Class

Represents a UTF-7 encoding of Unicode characters.

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

public class UTF7Encoding : Encoding

Encoding is the process of transforming a set of Unicode characters into a sequence of bytes. Decoding is the process of transforming a sequence of encoded bytes into a set of Unicode characters.

The UTF-7 encoding represents Unicode characters as sequences of 7-bit ASCII characters. This encoding supports certain protocols for which it is required, most often e-mail or newsgroup protocols. Since UTF-7 is not particularly secure or robust, UTF-8 should normally be preferred to UTF-7.


UTF7Encoding does not provide error detection. For security reasons, the application should use UTF8Encoding, UnicodeEncoding, or UTF32Encoding and enable error detection.

For more information about the UTFs and other encodings supported by System.Text, see Understanding Encodings and Using Unicode Encoding.

The GetByteCount method determines how many bytes result in encoding a set of Unicode characters, and the GetBytes method performs the actual encoding.

Likewise, the GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars and GetString methods perform the actual decoding.

UTF7Encoding corresponds to the Windows code page 65000.


The state of a UTF-7 encoded object is not preserved if the object is serialized and deserialized using different .NET Framework versions.

The following code example demonstrates how to use a UTF7Encoding to encode a string of Unicode characters and store them in a byte array. Notice that when the byte array is decoded back to a string, no data is lost.

using System;
using System.Text;

class UTF7EncodingExample {
    public static void Main() {
        // Create a UTF-7 encoding.
        UTF7Encoding utf7 = new UTF7Encoding();

        // A Unicode string with two characters outside a 7-bit code range.
        String unicodeString =
            "This Unicode string contains two characters " +
            "with codes outside a 7-bit code range, " +
            "Pi (\u03a0) and Sigma (\u03a3).";
        Console.WriteLine("Original string:");

        // Encode the string.
        Byte[] encodedBytes = utf7.GetBytes(unicodeString);
        Console.WriteLine("Encoded bytes:");
        foreach (Byte b in encodedBytes) {
            Console.Write("[{0}]", b);

        // Decode bytes back to string. 
        // Notice Pi and Sigma characters are still present.
        String decodedString = utf7.GetString(encodedBytes);
        Console.WriteLine("Decoded bytes:");


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0