What causing this “Invalid length for a Base-64 char array”

Question

I have very little to go on here. I can\'t reproduce this locally, but when users get the error I get an automatic email exception notification:

Answer 1

As Jon Skeet said, the string must be multiple of 4 bytes. But I was still getting the error.

At least it got removed in debug mode. Put a break point on Convert.FromBase64String() then step through the code. Miraculously, the error disappeared for me :) It is probably related to View states and similar other issues as others have reported.