Old but useful: http://weblogs.asp.net/leftslipper/archive/2007/06/29/how-asp-net-databinding-deals-with-eval-and-bind-statements.aspx
The “Bind” method for two-way databinding is pure magic, the ASP.NET parser intercepts it and translates it into real code.
This means that if you have a problem with an eval such as “System.InvalidCastException: Specified cast is not valid.”, which you can fix up just fine when using eval by manually casting or parsing the object, you simply won’t be able to use two way binding because there is no way to cast or parse the result of the eval.