将非托管unicode字符串编组到.net。高字符替换为问号

string input = "非托管Unicode字符串";
byte[] utf8Bytes = Encoding.UTF8.GetBytes(input);
byte[] utf16Bytes = Encoding.Convert(Encoding.UTF8, Encoding.Unicode, utf8Bytes);
string output = Encoding.Unicode.GetString(utf16Bytes);

string input = "非托管Unicode字符串";
string pattern = @"[\uD800-\uDBFF][\uDC00-\uDFFF]|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]";
string output = Regex.Replace(input, pattern, "?");