通常，当您提供

因此，如果您愿意尝试转换一个字节值大于255的字符（代码页1258 ），在这种情况下，您会得到？字符的后备。我的猜测是，在第一种情况下，输入字符串中的数据无效（也许字符看起来相同但不是正确的字符）。

So if you would e.g. try to convert a character with a byte value > 255 (which is not present in codepage 1258) you would get the fallback which is the ? character in this case. My guess is, that you have invalid data in the input string in the first case (maybe characters that look the same but are not the correct ones).

我的下一步将检查字符及其相应的字节值。

My next step would be to inspect the characters and their corresponding byte values.