CSLA .NET

I have a need to define validation rules in a database and have them loaded and applied at run time to my objects.

For example, in the database I would specify the property name, the rule, and (optionally) the value -- for example, property "MyString", rule "StringMaxLength", value 10.

Along those lines, I would also like to define dependencies between rules in the database as well (example:  if the value of this one boolean property is True, then make sure the length of this other string property is a maximum of 30)

Has anyone done anything like this (CSLA 3.0.4)?  any examples you'd like to share?

The rule implementations need to be written in code. But assuming you have that, then associating the rules with properties can be done from metadata.

What you need to know in the database are:

1. Business class name
2. Property name
3. Name of assembly containing rule class
4. Name of rule class
5. Name of rule method
6. Name/value list of parameters for rule

Items 1 and 2 are needed to identify which rules go with which properties of course.

Items 3-5 are necessary so you can use reflection to get at the specific rule method metadata and then create a delegate reference to that method.

Item 6 provides the parameters for the rule method. In CSLA .NET 3.0 I introduced the idea of DecoratedRuleArgs, which you can read about in the Using CSLA .NET 3.0 ebook. The purpose is specifically to make your scenario easier. The rules in CommonRules now all use DecoratedRuleArgs, so you can pass in parameters as name/value pairs instead of having to use the strongly-typed RuleArgs subclass for each rule.

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Rocky

Excellent!  Just what I was looking for.  This will help me to dynamically define validation rules in a database and apply them at run time.

Now for the second part of my question:  how can I dynamically define dependencies between properties in a database and apply them at run time?

Lhotka is it possible to let user wrte his own businessrule using some kind of scripting?

What kind of dependencies are you talking about?  Foreign key constraints, or something else?

ajj3085:

What kind of dependencies are you talking about?  Foreign key constraints, or something else?

 

Dependent properties, a la "if the value of property A changes, automatically run the validation code associated with property B"

See ValidationRules.AddDependentProperty

ajj3085:

See ValidationRules.AddDependentProperty

 

Doh!  (slaps forehead) I knew that.  I guess until now I just never put two and two together and realized all I need are the property names and the bi-directionalness in the database.

 

Thanks for pointing out the obvious.  :)