ASCIIEncoding Class

ASCIIEncoding Class

 

Represents an ASCII character encoding of Unicode characters.

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

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

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

NameDescription
System_CAPS_pubmethodASCIIEncoding()

Initializes a new instance of the ASCIIEncoding class.

NameDescription
System_CAPS_pubpropertyBodyName

When overridden in a derived class, gets a name for the current encoding that can be used with mail agent body tags.(Inherited from Encoding.)

System_CAPS_pubpropertyCodePage

When overridden in a derived class, gets the code page identifier of the current Encoding.(Inherited from Encoding.)

System_CAPS_pubpropertyDecoderFallback

Gets or sets the DecoderFallback object for the current Encoding object.(Inherited from Encoding.)

System_CAPS_pubpropertyEncoderFallback

Gets or sets the EncoderFallback object for the current Encoding object.(Inherited from Encoding.)

System_CAPS_pubpropertyEncodingName

When overridden in a derived class, gets the human-readable description of the current encoding.(Inherited from Encoding.)

System_CAPS_pubpropertyHeaderName

When overridden in a derived class, gets a name for the current encoding that can be used with mail agent header tags.(Inherited from Encoding.)

System_CAPS_pubpropertyIsBrowserDisplay

When 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.)

System_CAPS_pubpropertyIsBrowserSave

When 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.)

System_CAPS_pubpropertyIsMailNewsDisplay

When 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.)

System_CAPS_pubpropertyIsMailNewsSave

When 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.)

System_CAPS_pubpropertyIsReadOnly

When overridden in a derived class, gets a value indicating whether the current encoding is read-only.(Inherited from Encoding.)

System_CAPS_pubpropertyIsSingleByte

Gets a value indicating whether the current encoding uses single-byte code points.(Overrides Encoding.IsSingleByte.)

System_CAPS_pubpropertyWebName

When overridden in a derived class, gets the name registered with the Internet Assigned Numbers Authority (IANA) for the current encoding.(Inherited from Encoding.)

System_CAPS_pubpropertyWindowsCodePage

When overridden in a derived class, gets the Windows operating system code page that most closely corresponds to the current encoding.(Inherited from Encoding.)

NameDescription
System_CAPS_pubmethodClone()

When overridden in a derived class, creates a shallow copy of the current Encoding object.(Inherited from Encoding.)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified Object is equal to the current instance.(Inherited from Encoding.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetByteCount(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).)

System_CAPS_pubmethodGetByteCount(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.)

System_CAPS_pubmethodGetByteCount(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).)

System_CAPS_pubmethodGetByteCount(String)

Calculates the number of bytes produced by encoding the characters in the specified String.(Overrides Encoding.GetByteCount(String).)

System_CAPS_pubmethodGetBytes(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).)

System_CAPS_pubmethodGetBytes(Char[])

When overridden in a derived class, encodes all the characters in the specified character array into a sequence of bytes.(Inherited from Encoding.)

System_CAPS_pubmethodGetBytes(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.)

System_CAPS_pubmethodGetBytes(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).)

System_CAPS_pubmethodGetBytes(String)

When overridden in a derived class, encodes all the characters in the specified string into a sequence of bytes.(Inherited from Encoding.)

System_CAPS_pubmethodGetBytes(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).)

System_CAPS_pubmethodGetCharCount(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).)

System_CAPS_pubmethodGetCharCount(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.)

System_CAPS_pubmethodGetCharCount(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).)

System_CAPS_pubmethodGetChars(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).)

System_CAPS_pubmethodGetChars(Byte[])

When overridden in a derived class, decodes all the bytes in the specified byte array into a set of characters.(Inherited from Encoding.)

System_CAPS_pubmethodGetChars(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.)

System_CAPS_pubmethodGetChars(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).)

System_CAPS_pubmethodGetDecoder()

Obtains a decoder that converts an ASCII encoded sequence of bytes into a sequence of Unicode characters.(Overrides Encoding.GetDecoder().)

System_CAPS_pubmethodGetEncoder()

Obtains an encoder that converts a sequence of Unicode characters into an ASCII encoded sequence of bytes.(Overrides Encoding.GetEncoder().)

System_CAPS_pubmethodGetHashCode()

Returns the hash code for the current instance.(Inherited from Encoding.)

System_CAPS_pubmethodGetMaxByteCount(Int32)

Calculates the maximum number of bytes produced by encoding the specified number of characters.(Overrides Encoding.GetMaxByteCount(Int32).)

System_CAPS_pubmethodGetMaxCharCount(Int32)

Calculates the maximum number of characters produced by decoding the specified number of bytes.(Overrides Encoding.GetMaxCharCount(Int32).)

System_CAPS_pubmethodGetPreamble()

When overridden in a derived class, returns a sequence of bytes that specifies the encoding used.(Inherited from Encoding.)

System_CAPS_pubmethodGetString(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.)

System_CAPS_pubmethodGetString(Byte[])

When overridden in a derived class, decodes all the bytes in the specified byte array into a string.(Inherited from Encoding.)

System_CAPS_pubmethodGetString(Byte[], Int32, Int32)

Decodes a range of bytes from a byte array into a string.(Overrides Encoding.GetString(Byte[], Int32, Int32).)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodIsAlwaysNormalized()

Gets a value indicating whether the current encoding is always normalized, using the default normalization form.(Inherited from Encoding.)

System_CAPS_pubmethodIsAlwaysNormalized(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.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

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.

System_CAPS_cautionCaution

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);
    }
}
// The example displays the following output:
//    Original string:
//    This Unicode string contains two characters with codes outside the ASCII code ra
//    nge, Pi (Π) and Sigma (Σ).
//
//    Encoded bytes:
//    [84][104][105][115][32][85][110][105][99][111][100][101][32][115][116][114][105]
//    [110][103][32][99][111][110][116][97][105][110][115][32][116][119][111][32][99][
//    104][97][114][97][99][116][101][114][115][32][119][105][116][104][32][99][111][1
//    00][101][115][32][111][117][116][115][105][100][101][32][116][104][101][32][65][
//    83][67][73][73][32][99][111][100][101][32][114][97][110][103][101][44][32][80][1
//    05][32][40][63][41][32][97][110][100][32][83][105][103][109][97][32][40][63][41]
//    [46]
//
//    Value at position of Pi character: 63
//    Value at position of Sigma character: 63
//
//    Decoded bytes:
//    This Unicode string contains two characters with codes outside the ASCII code ra
//    nge, Pi (?) and Sigma (?).

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1

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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