title: Convert.FromBase64String() throws "invalid Base-64 string" error
body: <p>I have a key which is Base64 encoded.</p>
  
  <p>While trying to decode I am receiving the following error. The error is thrown by <code>byte[] todecode_byte = Convert.FromBase64String(data);</code> </p>
  
  <blockquote>
    <p>Error in base64DecodeThe input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or an illegal character among the padding characters. </p>
  </blockquote>
  
  <p>I am using the below method to decode this:</p>
  
  <pre><code>public string base64Decode(string data)
  {
      try
      {
          System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();
          System.Text.Decoder utf8Decode = encoder.GetDecoder();
  
          byte[] todecode_byte = Convert.FromBase64String(data); // this line throws the exception
  
          int charCount = utf8Decode.GetCharCount(todecode_byte, 0, todecode_byte.Length);
          char[] decoded_char = new char[charCount];
          utf8Decode.GetChars(todecode_byte, 0, todecode_byte.Length, decoded_char, 0);
          string result = new String(decoded_char);
          return result;
      }
      catch (Exception e)
      {
          throw new Exception("Error in base64Decode" + e.Message);
      }
  }
  </code></pre>