# Other .NET Programming > Windows Presentation Foundation (WPF) & XAML forum >  ValidationRule wrong namespace error

## BauerH

Hello,

iam working on that problem for 2 days now and i cant solve it.

I added a screenshot to this post. Both files are in the same namespace and the same folder, but i still get the error that there is no file DialogBoxValidationRule... any idears?

Best Wishes

Hans

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