How do I encode and decode a base64 string?

Question

1. How do I return a base64 encoded string given a string?

2. How do I decode a base64 encoded string into a string?

Answer 1

I'm sharing my implementation with some neat features:

• uses Extension Methods for Encoding class. Rationale is that someone may need to support different types of encodings (not only UTF8).
• Another improvement is failing gracefully with null result for null entry - it's very useful in real life scenarios and supports equivalence for X=decode(encode(X)).

Remark: Remember that to use Extension Method you have to (!) import the namespace with using keyword (in this case using MyApplication.Helpers.Encoding).

Code:

namespace MyApplication.Helpers.Encoding
{
    public static class EncodingForBase64
    {
        public static string EncodeBase64(this System.Text.Encoding encoding, string text)
        {
            if (text == null)
            {
                return null;
            }

            byte[] textAsBytes = encoding.GetBytes(text);
            return System.Convert.ToBase64String(textAsBytes);
        }

        public static string DecodeBase64(this System.Text.Encoding encoding, string encodedText)
        {
            if (encodedText == null)
            {
                return null;
            }

            byte[] textAsBytes = System.Convert.FromBase64String(encodedText);
            return encoding.GetString(textAsBytes);
        }
    }
}

Usage example:

using MyApplication.Helpers.Encoding; // !!!

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Test1();
            Test2();
        }

        static void Test1()
        {
            string textEncoded = System.Text.Encoding.UTF8.EncodeBase64("test1...");
            System.Diagnostics.Debug.Assert(textEncoded == "dGVzdDEuLi4=");

            string textDecoded = System.Text.Encoding.UTF8.DecodeBase64(textEncoded);
            System.Diagnostics.Debug.Assert(textDecoded == "test1...");
        }

        static void Test2()
        {
            string textEncoded = System.Text.Encoding.UTF8.EncodeBase64(null);
            System.Diagnostics.Debug.Assert(textEncoded == null);

            string textDecoded = System.Text.Encoding.UTF8.DecodeBase64(textEncoded);
            System.Diagnostics.Debug.Assert(textDecoded == null);
        }
    }
}