Viewing Embedded Images in HTML E-mail (Base64)

Problem

you have image data from an HTML e-mail, but don't know what to do

with it. When you save it to disk it comes out with a weird string instead of binary data.

Solution

pretty simple, you just have to know the terms. This string of data is actually Base64 encoded, which means that the binary data has been converted to a text string for easy transmission over text protocols. .Net Developer's Journal (dead link removed; SF 2025) has a good full explanation. All you have to do is convert the string over to a byte array using Convert.FromBase64String, then save your new byte[].

And what if the string is itself transmitted as a byte array? Well, simply convert each byte into a char and then convert the resulting array into the new byte array:

// Convert "string" to chars
byte[] byteEncodedString = ...;
char[] charBytes = new char[byteEncodedString.Length];
for (int i = 0; i < byteEncodedString.Length; i++)
     charBytes[i] = Convert.ToChar(byteEncodedString[i]);

// Convert chars back to bytes
byte[] newBytes = Convert.FromBase64CharAray(charBytes, 0, charBytes.Length);

// Save
using (FileStream fs = new FileStream(mypath, FileMode.Create))
     fs.Write(newBytes, 0, newBytes.Length);