Invalid length for a Base-64 char array.
异常信息
引用https://stackoverflow.com/questions/2925729/invalid-length-for-a-base-64-char-array
string base64string
int mod4 = base64string.Length % 4;
if (mod4 > 0 )
{
base64string += new string('=', 4 - mod4);
}
这个方法很给力