Interestingly enough, now that Microsoft has built this into WPF, we've built something even better in CSLA .NET for Silverlight - a PropertyStatus control.
PropertyStatus handles the different severities (error/warn/info), and does (on a per-control basis) what Authorizer does. In many ways I think it is a better solution than the current model.
So I'm considering creating a WPF version at some point - thought that may have to wait for some future release, as I doubt I'll have time for 3.6.
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