C# Base64密文轉換字符串報 "Base-64 字符數組或字符串的長度無效。" 問題記錄

做一下字符串替換以及PadRight操作就可以了：

string payloadstr = "eyJpZCI6MTMwNzkyNzA3NjUwNjE0MDY3MywiYWNjb3VudCI6InRlc3QiLCJ1c2VyS2V5IjoiMTIzIiwic3ViIjoiMTMwNzkyNzA3NjUwNjE0MDY3MyIsImlhdCI6MTYwMDY3OTM3OCwiZXhwIjoxNjAwNzY1Nzc4fQ";
string dummyData = payloadstr.Trim().Replace("%", "").Replace(",", "").Replace(" ", "+");
if (dummyData.Length % 4 > 0)
{
　　dummyData = dummyData.PadRight(dummyData.Length + 4 - dummyData.Length % 4, '=');
}
byte[] byteArray = Convert.FromBase64String(dummyData); 
Console.WriteLine(Encoding.UTF8.GetString(byteArray));