当使用ASCII编码并将字符串编码为字节时，像ö这样的字符将会变成?。
Encoding encoding = Encoding.GetEncoding("us-ascii"); // or Encoding encoding = Encoding.ASCI;
data = encoding.GetBytes(s);
我正在寻找一种方法来用不同的字符替换那些字符，而不仅仅是一个问号。
例如：
ä -> ae
ö -> oe
ü -> ue
ß -> ss
如果无法用多个字符来替换一个字符，即使我可以用一个字符来替换它（ö -> o），我也会接受。
现在有几种EncoderFallback的实现，但我不理解它们的工作原理。
一个快速而不完美的解决方案是，在将字符串传递给Encoding.GetBytes()之前替换所有这些字符，但这似乎不是“正确”的方法。
我希望我能够将替换表格提供给编码对象。
我该如何实现这一点？
Encoder.GetEncoding方法提供自定义类的实现，该类必须派生自EncoderFallback。不过，该类基本上只是真正工作的包装器，在EncoderFallbackBuffer中完成。您需要缓冲区的原因是回退不一定是一对一的过程；在您的示例中，您可能会将单个Unicode字符映射到两个ASCII字符。EncoderFallback 实现来创建EncoderFallbackBuffer 的实例。然后调用您自定义缓冲区的Fallback方法。true 。从那里开始，编码器将反复调用GetNextChar，只要Remaining> 0 和/或直到GetNextChar返回CP 0为止，并将这些字符粘贴到编码结果中。public class CustomMapper : EncoderFallback
{
// Use can override the "replacement character", so track what they
// give us.
public string DefaultString;
public CustomMapper() : this("*")
{
}
public CustomMapper(string defaultString)
{
this.DefaultString = defaultString;
}
public override EncoderFallbackBuffer CreateFallbackBuffer()
{
return new CustomMapperFallbackBuffer(this);
}
// This is the length of the largest possible replacement string we can
// return for a single Unicode code point.
public override int MaxCharCount
{
get { return 2; }
}
}
public class CustomMapperFallbackBuffer : EncoderFallbackBuffer
{
CustomMapper fb;
public CustomMapperFallbackBuffer(CustomMapper fallback)
{
// We can use the same custom buffer with different fallbacks, e.g.
// we might have different sets of replacement characters for different
// cases. This is just a reference to the parent in case we want it.
this.fb = fallback;
}
public override bool Fallback(char charUnknown, int index)
{
// Do the work of figuring out what sequence of characters should replace
// charUnknown. index is the position in the original string of this character,
// in case that's relevant.
// If we end up generating a sequence of replacement characters, return
// true, and the encoder will start calling GetNextChar. Otherwise return
// false.
// Alternatively, instead of returning false, you can simply extract
// DefaultString from this.fb and return that for failure cases.
}
public override bool Fallback(char charUnknownHigh, char charUnknownLow, int index)
{
// Same as above, except we have a UTF-16 surrogate pair. Same rules
// apply: if we can map this pair, return true, otherwise return false.
// Most likely, you're going to return false here for an ASCII-type
// encoding.
}
public override char GetNextChar()
{
// Return the next character in our internal buffer of replacement
// characters waiting to be put into the encoded byte stream. If
// we're all out of characters, return '\u0000'.
}
public override bool MovePrevious()
{
// Back up to the previous character we returned and get ready
// to return it again. If that's possible, return true; if that's
// not possible (e.g. we have no previous character) return false;
}
public override int Remaining
{
// Return the number of characters that we've got waiting
// for the encoder to read.
get { return count < 0 ? 0 : count; }
}
public override void Reset()
{
// Reset our internal state back to the initial one.
}
}
GetBytes()？ - joe