A particular build/compile error in my Silverlight project has been plaguing me today. Unfortunately while changing a million things in a Xaml view, I managed to stuff it up chronic. So much so, that it was a nightmare to trace back to the root cause. Funny that… it smacks to me of a similar time I had Xaml compilation error 60 but this is different.


Compiling my Silverlight 3 application prompted the following error.

Error 1: The “ValidateXaml” task failed unexpectedly.

Could be a number of things, but firstly check if you had a CheckBox defined in your Xaml, and that you changed something on it. If you do, then it’s most likely the culprit and read on…



In my particular case, CheckBox was incorrectly bound for it’s checked/ticked state.

<CheckBox Checked = “{Binding Path=SomeProperty”} />

Seems innocent doesn’t it. However, the Checked attribute of the CheckBox is actually an event, not a property! This causes the build task to blow a fuse – wish it would actually tell me the proper reason.

Thus the , proper syntax is…

<CheckBox IsChecked = “{Binding Path=SomeProperty”} />


I hope that saved you a bit of head scratching!


This is a cross post from my EMC blog, mainly for backup duplicity and to aggregate some of my past postings. My EMC blog used to be under the Conchango brand but was acquired by EMC so I’ve also retrospectively refreshed some of the old links too. permalink to the original post here