Aspect Oriented Programming(AOP) with PostSharp in C# .NET - Example

Introduction

Using the code

Suppose in your C# .NET application you have a requirement that you want to log the Entry and Exit of every method. One of the ways to do this is by writing log statements at every start and end of the method but that will be a performance nightmare.

Here comes the magic of AOP!

 AOP is something that increases the modularity by allowing separation of concern which in this case is Logging.Now you could read about Aspect Oriented Programming over the net but that is not the topic of today.

There are a number of frameworks that are based on AOP like Castle, Encase, Spring .NET amd one of them is PostSharp.

Today we will see how to do Entry/Exit level logging at every method using PostSharp.

You could download free edition of PostSharp from here

http://www.postsharp.net/download

Now add a reference of PostSharp.dll to your C# project. Create a attribute something like below

[Serializable]
    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = false)]
    [MulticastAttributeUsage(MulticastTargets.Method, AllowMultiple = true)]
    public class LoggingAttribute : OnMethodBoundaryAspect
    {
         public override void OnEntry(MethodExecutionArgs args)
        {
           Console.WriteLine("On Method Enter");
        }

        public override void OnExit(MethodExecutionArgs args)
        {
           Console.WriteLine("On Method Exit");
        }
    }

[Logging]
public void Test()
{
}