Question

I have a bunch of methods with varying signatures. These methods interact with a fragile data connection, so we often use a helper class to perform retries/reconnects, etc. Like so:

MyHelper.PerformCall( () => { doStuffWithData(parameters...) });

And this works fine, but it can make the code a little cluttery. What I would prefer to do is decorate the methods that interact with the data connection like so:

[InteractsWithData]
protected string doStuffWithData(parameters...)
{
     // do stuff...
}

And then essentially, whenever doStuffWithData is called, the body of that method would be passed in as an Action to MyHelper.PerformCall(). How do I do this?

Answer 1

.NET Attributes are meta-data, not decorators / active components that automatically get invoked. There is no way to achieve this behaviour.

You could use attributes to implement decorators by putting the decorator code in the Attribute class and call the method with a helper method that invokes the method in the Attribute class using Reflection. But I’m not sure this would be a big improvement over just calling the “decorator-method” directly.

“Decorator-Attribute”:

[AttributeUsage(AttributeTargets.Method)]
public class MyDecorator : Attribute
{
    public void PerformCall(Action action)
    {
       // invoke action (or not)
    }
}

Method:

[MyDecorator]
void MyMethod()
{
}

Usage:

InvokeWithDecorator(() => MyMethod());

Helper method:

void InvokeWithDecorator(Expression<Func<?>> expression)
{
    // complicated stuff to look up attribute using reflection
}

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Have a look at frameworks for Aspect Oriented Programming in C#. These may offer what you want.