The demo site shows the ContextKeys property as a way to pass some extra values with the file upload post but it does not work and looking at the source code the property exists but does not appear to be used anywhere in code server side nor client side. I guess it was planned but never implemented.
If this property really worked the control would be much more useful.
If it will never be implemented then it should be removed from the documentation and sample web site.
Comments: I'm not really sure if this is the case. The ContectKey is just a property which you can use but there is an issue when having 2 AjaxFileUpload controls on the same page. The ContextKey value is always the one of the first control on the page. Same as: http://ajaxcontroltoolkit.codeplex.com/workitem/27175
If this property really worked the control would be much more useful.
If it will never be implemented then it should be removed from the documentation and sample web site.
Comments: I'm not really sure if this is the case. The ContectKey is just a property which you can use but there is an issue when having 2 AjaxFileUpload controls on the same page. The ContextKey value is always the one of the first control on the page. Same as: http://ajaxcontroltoolkit.codeplex.com/workitem/27175