ソースコード using System.Text; public static class StringExtensions { public static string ToShiftJis( this string unicodeStrings ) { var unicode = Encoding.Unicode; var unicodeByte = unicode.GetBytes( unicodeStrings ); var s_jis = Encoding.GetEncoding( "shift_jis" ); var s_jisByte = Encoding.Convert( unicode, s_jis, unicodeByte ); var s_jisChars = new char[ s_jis.GetCharCount( s_jisByte, 0, s_jisByte.
![【C#】Unicode 文字列から Shift-JIS 文字列に変換して返す拡張メソッド - コガネブログ](https://cdn-ak-scissors.b.st-hatena.com/image/square/31ff576eced8049fb4af85ea8cafa72a5620e337/height=288;version=1;width=512/https%3A%2F%2Fcdn-ak.f.st-hatena.com%2Fimages%2Ffotolife%2Fb%2Fbaba_s%2F20180826%2F20180826160156.png)