.net - 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:

Invalid length for a Base-64 char array.

  at System.Convert.FromBase64String(String s)
  at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
  at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState)
  at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)
  at System.Web.UI.HiddenFieldPageStatePersister.Load()

I'm inclined to think there is a problem with data that is being assigned to viewstate. For example:

List<int> SelectedActionIDList = GetSelectedActionIDList();
ViewState["_SelectedActionIDList"] = SelectedActionIDList;

It's difficult to guess the source of the error without being able to reproduce the error locally.

If anyone has had any experience with this error, I would really like to know what you found out.

Answer 1

After urlDecode processes the text, it replaces all '+' chars with ' ' ... thus the error. You should simply call this statement to make it base 64 compatible again:

        sEncryptedString = sEncryptedString.Replace(' ', '+');