把 ANSI來編碼 另存 成 U8 的文字檔

參考
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string fn = Server.MapPath("rand.txt");
FileStream fsSource = new FileStream(Server.MapPath(".") + @"\rand.txt",FileMode.Open); //Source File
FileStream fsDest = new FileStream(Server.MapPath(".") + @"\rand2.txt",FileMode.OpenOrCreate,FileAccess.ReadWrite); // Desc File
byte[] S_Byte =new byte[fsSource.Length];
fsSource.Read(S_Byte,0,Convert.ToInt32(fsSource.Length)); // Read Bytes from Source
byte[] D_Byte = System.Text.Encoding.Convert(System.Text.Encoding.Default,System.Text.Encoding.UTF8,S_Byte); // Bytes Encode Covert
fsDest.Write(D_Byte,0,D_Byte.Length); //Write File.
fsSource.Close();
fsDest.Close();