如何：在旧式编码与 Unicode 之间转换（C# 编程指南）
在 C# 中，内存中的所有字符串都是按 Unicode (UTF-16) 编码的。将数据从存储器移动到 string 对象中后，数据将自动转换为 UTF-16。如果数据仅包含从 0 到 127 的 ASCII 值，则此转换无需您执行任何额外的工作。但若源文本包含扩展的 ASCII 字节值（128 到 255），则默认情况下，将根据当前代码页解释扩展字符。若要指定应该根据其他某个代码页解释源文本，请使用 System.Text.Encoding 类，如下面的示例所示。
下面的示例演示如何转换按 8 位 ASCII 编码的文本文件，此转换根据 Windows 代码页 737 解释源文本。
class ANSIToUnicode
{
static void Main()
{
// Create a file that contains the Greek work ψυχή (psyche) when interpreted by using
// code page 737 ((DOS) Greek). You can also create the file by using Character Map
// to paste the characters into Microsoft Word and then "Save As" by using the DOS
// (Greek) encoding. (Word will actually create a six-byte file by appending "\r\n" at the end.)
System.IO.File.WriteAllBytes(@"greek.txt", new byte[] { 0xAF, 0xAC, 0xAE, 0x9E });
// Specify the code page to correctly interpret byte values
Encoding encoding = Encoding.GetEncoding(737); //(DOS) Greek code page
byte[] codePageValues = System.IO.File.ReadAllBytes(@"greek.txt");
// Same content is now encoded as UTF-16
string unicodeValues = encoding.GetString(codePageValues);
// Show that the text content is still intact in Unicode string
// (Add a reference to System.Windows.Forms.dll)
System.Windows.Forms.MessageBox.Show(unicodeValues);
// Same content "ψυχή" is stored as UTF-8
System.IO.File.WriteAllText(@"greek_unicode.txt", unicodeValues);
// Conversion is complete. Show the bytes to prove the conversion.
Console.WriteLine("8-bit encoding byte values:");
foreach(byte b in codePageValues)
Console.Write("{0:X}-", b);
Console.WriteLine();
Console.WriteLine("Unicode values:");
string unicodeString = System.IO.File.ReadAllText("greek_unicode.txt");
System.Globalization.TextElementEnumerator enumerator =
System.Globalization.StringInfo.GetTextElementEnumerator(unicodeString);
while(enumerator.MoveNext())
{
string s = enumerator.GetTextElement();
int i = Char.ConvertToUtf32(s, 0);
Console.Write("{0:X}-", i);
}
Console.WriteLine();
// Keep the console window open in debug mode.
Console.Write("Press any key to exit.");
Console.ReadKey();
}
/*
* Output:
8-bit encoding byte values:
AF-AC-AE-9E
Unicode values:
3C8-3C5-3C7-3B7
*/
}