2009-10-30 AOP in .NET with Unity Interception Model

2009-10-30 aop-in-net-with-unity-interception-model

# Title: AOP in .NET with Unity Interception Model
# Author: Mikael Lundin
# Link: http://blog.mikaellundin.name/2009/10/30/aop-in-net-with-unity-interception-model.html

AnyMatchingRule.cs

public class AnyMatchingRule : IMatchingRule
{
    public bool Matches(MethodBase member)
    {
        return true;
    }
}

Container.cs

public class Container : UnityContainer
{
    public void Configure()
    {
        /* Register types into the container */
        RegisterType<IDataFactory, StubDataFactory>();
        RegisterType<IDataAccess<Customer>, CustomerDataAccess>();
 
        /* Register our matching rule and call handler */
        RegisterType<IMatchingRule, AnyMatchingRule>("AnyMatchingRule");
        RegisterType<ICallHandler, LogCallHandler>("LogCallHandler");
 
        /* Create a new policy and reference the matching rule and call handler by name */
        AddNewExtension<Interception>();
        Configure<Interception>().AddPolicy("LogPolicy")
            .AddMatchingRule("AnyMatchingRule")
            .AddCallHandler("LogCallHandler");
 
        /* Make IDataAccess interface elegible for interception */
        Configure<Interception>().SetInterceptorFor(typeof(IDataAccess<>), new TransparentProxyInterceptor());
    }
}

DataAccess.cs

public Customer GetById(int id)
{
    System.Diagnostics.Debug.WriteLine("CustomerDataAccess.GetById(" + id + ")"); // Noise
    Customer result = null;
 
    using (var connection = dataFactory.OpenConnection())
    {
        var command = connection.CreateCommand();
        command.CommandText = "SELECT * FROM Customer WHERE id=" + id; // Beware of SQL injection
 
        var reader = command.ExecuteReader();
        result = reader.GetCustomer();
    }
 
    System.Diagnostics.Debug.WriteLine("CustomerDataAccess.GetById(" + id + ") -> " + result);
    return result;
}

Example1.cs

var repository = Container.Instance.Resolve<CustomerRepository>();
var customer = repository.GetCustomerById(1);

Example2.cs

var container = new Container();
container.Configure();
 
var dataAccess = container.Resolve<IDataAccess<Customer>>();
dataAccess.GetById(1);

LogCallHandler.cs

public class LogCallHandler : ICallHandler
{
    public IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext)
    {
        string className = input.MethodBase.DeclaringType.Name;
        string methodName = input.MethodBase.Name;
        string arguments = GetArgumentList(input.Arguments);
 
        /* CustomerDataAccess.GetById(123) */
        string preMethodMessage = string.Format("{0}.{1}({2})", className, methodName, arguments);
        System.Diagnostics.Debug.WriteLine(preMethodMessage);
 
        /* Call the method that was intercepted */
        IMethodReturn msg = getNext()(input, getNext);
 
        string postMethodMessage = string.Format("{0}.{1}() -> {2}", className, methodName, msg.ReturnValue);
        System.Diagnostics.Debug.WriteLine(postMethodMessage);
 
        return msg;
    }
 
    public int Order { get; set; }
}