Basically, what the title says. I have several properties that combine together to really make one logical answer, and i would like to run a server-side validation code (that i write) which take these multiple fields into account and hook up to only one validation output/error message that users see on the webpage.

I looked at scott guthries method of extending an attribute and using it in yoru dataannotations declarations, but, as i can see, there is no way to declare a dataannotations-style attribute on multiple properties, and you can only place the declarations (such as [Email], [Range], [Required]) over one property :(.

i have looked at the PropertiesMustMatchAttribute in the default mvc 2.0 project that appears when you start a new project, this example is as useful as using a pair of pins to check your motor oil - useless!

i have tried this method, however, creating a class level attribute, and have no idea how to display the error from this in my aspx page. i have tried html.ValidationMessage("ClassNameWhereAttributeIsAdded") and a variety of other thing, and it has not worked. and i should mention, there is NOT ONE blog post on doing validation at this level - despite this being a common need in any project or business logic scenario!

can anyone help me in having my message displayed in my aspx page, and also if possible a proper document or reference explaining validation at this level?