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ASCIIEncoding Class

Represents an ASCII character encoding of Unicode characters.

System.Object
  System.Text.Encoding
    System.Text.ASCIIEncoding

Namespace:  System.Text
Assemblies:   mscorlib (in mscorlib.dll)
  System.Text.Encoding.Extensions (in System.Text.Encoding.Extensions.dll)

[SerializableAttribute]
[ComVisibleAttribute(true)]
public class ASCIIEncoding : Encoding

The ASCIIEncoding type exposes the following members.

  NameDescription
Public methodSupported by the XNA FrameworkASCIIEncodingInitializes a new instance of the ASCIIEncoding class.
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  NameDescription
Public propertyBodyNameWhen overridden in a derived class, gets a name for the current encoding that can be used with mail agent body tags. (Inherited from Encoding.)
Public propertySupported by the XNA FrameworkCodePageWhen overridden in a derived class, gets the code page identifier of the current Encoding. (Inherited from Encoding.)
Public propertyDecoderFallbackGets or sets the DecoderFallback object for the current Encoding object. (Inherited from Encoding.)
Public propertyEncoderFallbackGets or sets the EncoderFallback object for the current Encoding object. (Inherited from Encoding.)
Public propertyEncodingNameWhen overridden in a derived class, gets the human-readable description of the current encoding. (Inherited from Encoding.)
Public propertyHeaderNameWhen overridden in a derived class, gets a name for the current encoding that can be used with mail agent header tags. (Inherited from Encoding.)
Public propertyIsBrowserDisplayWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by browser clients for displaying content. (Inherited from Encoding.)
Public propertyIsBrowserSaveWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by browser clients for saving content. (Inherited from Encoding.)
Public propertyIsMailNewsDisplayWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by mail and news clients for displaying content. (Inherited from Encoding.)
Public propertyIsMailNewsSaveWhen overridden in a derived class, gets a value indicating whether the current encoding can be used by mail and news clients for saving content. (Inherited from Encoding.)
Public propertyIsReadOnlyWhen overridden in a derived class, gets a value indicating whether the current encoding is read-only. (Inherited from Encoding.)
Public propertyIsSingleByteGets a value indicating whether the current encoding uses single-byte code points. (Overrides Encoding.IsSingleByte.)
Public propertySupported by the XNA FrameworkWebNameWhen overridden in a derived class, gets the name registered with the Internet Assigned Numbers Authority (IANA) for the current encoding. (Inherited from Encoding.)
Public propertyWindowsCodePageWhen overridden in a derived class, gets the Windows operating system code page that most closely corresponds to the current encoding. (Inherited from Encoding.)
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  NameDescription
Public methodSupported by the XNA FrameworkCloneWhen overridden in a derived class, creates a shallow copy of the current Encoding object. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkEqualsDetermines whether the specified Object is equal to the current instance. (Inherited from Encoding.)
Protected methodSupported by the XNA FrameworkFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGetByteCount(Char[])When overridden in a derived class, calculates the number of bytes produced by encoding all the characters in the specified character array. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetByteCount(String)Calculates the number of bytes produced by encoding the characters in the specified String. (Overrides Encoding.GetByteCount(String).)
Public methodGetByteCount(Char*, Int32)Calculates the number of bytes produced by encoding a set of characters starting at the specified character pointer. (Overrides Encoding.GetByteCount(Char*, Int32).)
Public methodSupported by the XNA FrameworkGetByteCount(Char[], Int32, Int32)Calculates the number of bytes produced by encoding a set of characters from the specified character array. (Overrides Encoding.GetByteCount(Char[], Int32, Int32).)
Public methodSupported by the XNA FrameworkGetBytes(Char[])When overridden in a derived class, encodes all the characters in the specified character array into a sequence of bytes. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetBytes(String)When overridden in a derived class, encodes all the characters in the specified string into a sequence of bytes. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetBytes(Char[], Int32, Int32)When overridden in a derived class, encodes a set of characters from the specified character array into a sequence of bytes. (Inherited from Encoding.)
Public methodGetBytes(Char*, Int32, Byte*, Int32)Encodes a set of characters starting at the specified character pointer into a sequence of bytes that are stored starting at the specified byte pointer. (Overrides Encoding.GetBytes(Char*, Int32, Byte*, Int32).)
Public methodSupported by the XNA FrameworkGetBytes(Char[], Int32, Int32, Byte[], Int32)Encodes a set of characters from the specified character array into the specified byte array. (Overrides Encoding.GetBytes(Char[], Int32, Int32, Byte[], Int32).)
Public methodSupported by the XNA FrameworkGetBytes(String, Int32, Int32, Byte[], Int32)Encodes a set of characters from the specified String into the specified byte array. (Overrides Encoding.GetBytes(String, Int32, Int32, Byte[], Int32).)
Public methodSupported by the XNA FrameworkGetCharCount(Byte[])When overridden in a derived class, calculates the number of characters produced by decoding all the bytes in the specified byte array. (Inherited from Encoding.)
Public methodGetCharCount(Byte*, Int32)Calculates the number of characters produced by decoding a sequence of bytes starting at the specified byte pointer. (Overrides Encoding.GetCharCount(Byte*, Int32).)
Public methodSupported by the XNA FrameworkGetCharCount(Byte[], Int32, Int32)Calculates the number of characters produced by decoding a sequence of bytes from the specified byte array. (Overrides Encoding.GetCharCount(Byte[], Int32, Int32).)
Public methodSupported by the XNA FrameworkGetChars(Byte[])When overridden in a derived class, decodes all the bytes in the specified byte array into a set of characters. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetChars(Byte[], Int32, Int32)When overridden in a derived class, decodes a sequence of bytes from the specified byte array into a set of characters. (Inherited from Encoding.)
Public methodGetChars(Byte*, Int32, Char*, Int32)Decodes a sequence of bytes starting at the specified byte pointer into a set of characters that are stored starting at the specified character pointer. (Overrides Encoding.GetChars(Byte*, Int32, Char*, Int32).)
Public methodSupported by the XNA FrameworkGetChars(Byte[], Int32, Int32, Char[], Int32)Decodes a sequence of bytes from the specified byte array into the specified character array. (Overrides Encoding.GetChars(Byte[], Int32, Int32, Char[], Int32).)
Public methodSupported by the XNA FrameworkGetDecoderObtains a decoder that converts an ASCII encoded sequence of bytes into a sequence of Unicode characters. (Overrides Encoding.GetDecoder().)

In XNA Framework 3.0, this member is inherited from Encoding.GetDecoder().
Public methodSupported by the XNA FrameworkGetEncoderObtains an encoder that converts a sequence of Unicode characters into an ASCII encoded sequence of bytes. (Overrides Encoding.GetEncoder().)

In XNA Framework 3.0, this member is inherited from Encoding.GetEncoder().
Public methodSupported by the XNA FrameworkGetHashCodeReturns the hash code for the current instance. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetMaxByteCountCalculates the maximum number of bytes produced by encoding the specified number of characters. (Overrides Encoding.GetMaxByteCount(Int32).)
Public methodSupported by the XNA FrameworkGetMaxCharCountCalculates the maximum number of characters produced by decoding the specified number of bytes. (Overrides Encoding.GetMaxCharCount(Int32).)
Public methodSupported by the XNA FrameworkGetPreambleWhen overridden in a derived class, returns a sequence of bytes that specifies the encoding used. (Inherited from Encoding.)
Public methodGetString(Byte[])When overridden in a derived class, decodes all the bytes in the specified byte array into a string. (Inherited from Encoding.)
Public methodGetString(Byte*, Int32)When overridden in a derived class, decodes a specified number of bytes starting at a specified address into a string. (Inherited from Encoding.)
Public methodSupported by the XNA FrameworkGetString(Byte[], Int32, Int32)Decodes a range of bytes from a byte array into a string. (Overrides Encoding.GetString(Byte[], Int32, Int32).)

In XNA Framework 3.0, this member is inherited from Encoding.GetString(Byte[], Int32, Int32).
Public methodSupported by the XNA FrameworkGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsAlwaysNormalized()Gets a value indicating whether the current encoding is always normalized, using the default normalization form. (Inherited from Encoding.)
Public methodIsAlwaysNormalized(NormalizationForm)When overridden in a derived class, gets a value indicating whether the current encoding is always normalized, using the specified normalization form. (Inherited from Encoding.)
Protected methodSupported by the XNA FrameworkMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by the XNA FrameworkToStringReturns a string that represents the current object. (Inherited from Object.)
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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.

ASCIIEncoding corresponds to the Windows code page 20127. Because ASCII is a 7-bit encoding, ASCII characters are limited to the lowest 128 Unicode characters, from U+0000 to U+007F. If you use the default encoder returned by the Encoding.ASCII property or the ASCIIEncoding constructor, characters outside that range are replaced with a question mark (?) before the encoding operation is performed. Because the ASCIIEncoding class supports only a limited character set, the UTF8Encoding, UnicodeEncoding, and UTF32Encoding classes are better suited for globalized applications. The following considerations can help you to decide whether to use ASCIIEncoding:

  • Some protocols require ASCII or a subset of ASCII. In these cases ASCII encoding is appropriate.

  • If an 8-bit encoding is expected, then ASCII probably isn't the correct choice. Instead, consider using UTF8 instead of ASCII. For the characters U+0000 through U+007F, the results are identical, but all Unicode characters are representable in UTF-8, which avoids data loss.

Caution noteCaution

ASCIIEncoding does not provide error detection. For security reasons, you should use UTF8Encoding, UnicodeEncoding, or UTF32Encoding and enable error detection.

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.

Note that the default ASCIIEncoding constructor by itself might not have the appropriate behavior for your application. You might want to consider setting the EncoderFallback or DecoderFallback property to EncoderExceptionFallback or DecoderExceptionFallback to prevent sequences with the 8th bit set. Custom behavior might also be appropriate for these cases.

The following example demonstrates how to encode Unicode characters into ASCII. Notice the loss of data that occurs when your application uses ASCIIEncoding to encode Unicode characters outside of the ASCII range.

using System;
using System.Text;

class ASCIIEncodingExample {
    public static void Main() {
        // The encoding.
        ASCIIEncoding ascii = new ASCIIEncoding();

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

        // Save positions of the special characters for later reference. 
        int indexOfPi = unicodeString.IndexOf('\u03a0');
        int indexOfSigma = unicodeString.IndexOf('\u03a3');

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

        // Notice that the special characters have been replaced with 
        // the value 63, which is the ASCII character code for '?'.
        Console.WriteLine();
        Console.WriteLine(
            "Value at position of Pi character: {0}",
            encodedBytes[indexOfPi]
        );
        Console.WriteLine(
            "Value at position of Sigma character: {0}",
            encodedBytes[indexOfSigma]
        );

        // Decode bytes back to string. 
        // Notice missing Pi and Sigma characters.
        String decodedString = ascii.GetString(encodedBytes);
        Console.WriteLine();
        Console.WriteLine("Decoded bytes:");
        Console.WriteLine(decodedString);
    }
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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