Question on Generics

[Serenarules]

There's something I don't completely understand about generics. Can somebody elaborate based on the below.

Consider the following code:

public class SampleProcessor(Of TModel)

public function DoSomething(byval m as TModel) as boolean
' m.PropertyName doesn't work here as you might expect
end function

end class

How do I access the methods and properties of the input instance? I could use CallByName or reflection I suppose, but one seems antiquainted, and the other I no little about. There has to be a simpler way.

[dhtmlgod]

What your missing is your constraints. Constraints allow you to define an restriction on the type that can be used. I can't find the VB.NET documentation, but here is a link to the C# documentation: http://msdn.microsoft.com/en-us/library/d5x73970.aspx

Basically, what you are looking to do is set the constraint to an abstract base class or an interface, and all the types you want to use this generic class with must inherit from it.

public class SampleProcessor(Of TModel as BaseType)
 
public function DoSomething(byval m as TModel) as boolean
' m.PropertyName doesn't work here as you might expect
end function
 
end class

Constraints can also be applied at the method level too.

[Serenarules]

Right, I'm aware of that and IComparable etc...the things is, these classes dont' HAVE a base class. They are simple MVC models with nothing but properties. I don't know of a way to give them a base functionality. Am I just out of luck on this one?

[dhtmlgod]

If your not willing to use a common base type, then you are outta luck. I would rethink your design if your not willing to use a base type.

[Serenarules]

It's not that I'm not willing. I'd actually love to. I just don't see how. Maybe you can see things from a different angle. Here are two sample of the types of objects that would be passed in. I've omitted the actual get-set code for brevity.

public class ThisThing

private _Value as string

public propetry Value as string ...

end class

public class OtherThing

private _Value as integer

public propetry Value as integer ...

end class

So as you can see, with only simple properties like this, I'm not sure a base class can be derived. What would you suggest in this case to make my validators more flexible?

[dhtmlgod]

If you looking for validating view model values, I would highly recommend checking out Castle Windsor's Validation framework: http://www.castleproject.org/activer...alidation.html or the Data Annotations stuff that comes with .NET 3.5 http://www.asp.net/learn/mvc/tutorial-39-cs.aspx

You can integrate both validation frameworks with Mvc more using xVal too: http://xval.codeplex.com/