Question

Well i need some help here i don’t know how to solve this problem.

the function of the attribute is to determine if the function can be run…

So what i need is the following:

1. The consumer of the attribute should
   be able to determine if it can be
   executed.
2. The owner of the attribute should be
   able to tell the consumer that now it
   can/can’t be executed (like a
   event).
3. It must have a simple syntax.

This is what i have so far but it only implements point 1, 3.

[AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
public class ExecuteMethodAttribute : Attribute
{
    private Func<object, bool> canExecute;
    public Func<object, bool> CanExecute
    {
        get
        {
            return canExecute;
        }
    }


    public ExecuteMethodAttribute()
    {

    }

    public ExecuteMethodAttribute(Func<object, bool> canExecute)
    {
        this.canExecute = canExecute;
    }
}

Answer 1

Attributes are not intended for this type of purpose. You decorate a Type with an attribute, not a specific instance.

If you need a way to specify, to a consumer, that a specific method is ready to execute, or cannot execute, I would rethink your design. Instead of using an attribute, perhaps making a custom class would work much more appropriately.

Given your design, I would recommend taking a look at the ICommand interface. This basically does exactly what you are trying to do. It encapsulates a delegate into a class, with a “CanExecute” method, and an event for notifying “consumers” that the execution availability has changed. This would be a more appropriate option.