Inputting "こんにちは。元気ですか？" caused an application error: [ArgumentException: Error serializing value 'ᄳᅳᅋᅁᅏტ㈣䳷ᅇᄹᄫ�' of type 'System.String.'] After realizing

Inputting "こんにちは。元気ですか？" caused an application error: [ArgumentException: Error serializing value 'ᄳᅳᅋᅁᅏტ㈣䳷ᅇᄹᄫ�' of type 'System.String.'] After realizing it was "？" that was breaking everything, I ended up with this round trip: "こんにちは。元気ですか。" → "ᄳᅳᅋᅁᅏტ㈣䳷ᅇᄹᄫტ" → "こんにちは。ጃ⷗ですか。" It's broken. I suspect Unicode requires more careful manipulation than OP anticipated. :-)