Question

I’m new to C# development,
the following code is Convert.ToBase64String problem,
i don’t know how to solve it.

 byte[] str1Byte = System.Text.Encoding.UTF8.GetBytes("xyz123");
 String plaintext = Convert.ToBase64String(str1Byte);

 byte[] plaintext_bytes = System.Text.Encoding.UTF8.GetBytes(plaintext);
 Console.WriteLine("base64 plaintext: " + plaintext);
 Console.WriteLine("plaintext_bytes to String: " + 
                   System.Text.Encoding.UTF8.GetString(plaintext_bytes));
 Console.WriteLine("ToBase64String(plaintext_bytes) : " + 
                   Convert.ToBase64String(plaintext_bytes));

Result:

base64 plaintext: eHl6MTIz 
plaintext_bytes to String: eHl6MTIz 
ToBase64String(plaintext_bytes) : ZUhsNk1USXo= 

I expect the output of “Convert.ToBase64String(plaintext_bytes))” to be “eHl6MTIz“, not “ZUhsNk1USXo=“.

Answer 1

You’re trying to Base64 encode something that is already Base64 encoded:

// plaintext_bytes = eHl6MTIz 
Console.WriteLine("ToBase64String(plaintext_bytes) : " + Convert.ToBase64String(plaintext_bytes));

As mentioned, you need to go FROM base 64