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You are using this static class more like a library for common methods helpful for a controller. It's certainly not uncommon for developers to create such static libraries of commonly used methods and often the library will contain methods that might have little in common.

However in this case since all the methods are intended to be used by a Controller you could instead created a class, perhaps called Base Controller that inherits from Controller and implements these methods (not as statics). Then you can have the controllers in your website inherit from BaseController. This will make these convenience methods available to your controller without having to reference a static class. This approach is also widely used and could be a better choice in for your particular case.