Back to Basics: Delegates, Anonymous Methods and Lambda Expressions

published 4 days, 11 hours ago, submitted by EtienneTremblay 4 days, 16 hours ago

codebetter.com — Great article on .NET basics read more...

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unit testing your events

dotnettoad.com — In this article I will show you how you can unit test your events. I will show you a simple technique that will enable you to test if your events fire exactly as often as you want them to and I will provide you with two implementations. One implementation works well with the .NET Framework 2.0 and the second one uses .NET 3.0 (anonymous methods) in order to minimize the code necessary. read more...

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Reflecting on reflection

submitted by animaonline 9 months, 18 days ago

softscenario.blogspot.com — Some weeks ago I was working on a project where we receive some ten or twenty different message types from a server, and they all need to be handled when they arrive. Of course, we want to use event driven programming to make this happen on the fly, instead of polling all the time. All of the messages have the header in common, so we already made a abstract parent class called Message, and when it came to handling all the different messages, we wanted to write as little code as possible. So we added an abstract method called HandleResponse to the code. So the idea was to identify the incoming message type and invoke the HandleResponse using reflection on the object that we had identified this as. To do this, we made a little xml file that contains the message code (A-Z) along with the name and reference to the class linked to the message type. When the program starts, it reads the xml into a dictionary, so we can look up the key (message code) and get the class reference in return. XDocument descriptorsXml = XDocument.Load( @".\Data\MessageDescriptors.xml"); var descQuery = from desc in descriptorsXml.Descendants("Message") select new MessageDescriptor { Code = desc.Element("Code").Value, Name = desc.Element("Name").Value, ObjectType = desc.Element("ObjectType").Value.ToType() , IsServerMessage = Convert.ToBoolean( desc.Element("IsServerMessage").Value ) }; foreach (MessageDescriptor m in descQuery) { descriptors.Add(m.Code, m); } Then, we have a MessageHandlingFactory that simply gets objects in from a queue, identifies the type, and invokes the HandleResponse. If the object isn't recognized (could be a new message type, or could be that the programmer forgot to insert the description in the XML file), the MessageHandlingFactory can either throw an exception, or better yet, return a string with message that tells the user what went wrong. If everything goes as planned, it returns a string with the identified typename. object theType = Activator.CreateInstance(t, SessionID); EventInfo eInfo = t.GetEvent("OnWriteEvent"); Message.WriteEventHandler theHandler = new Message.WriteEventHandler(OnWriteEventHandler); eInfo.AddEventHandler(theType, theHandler); theType.GetType().GetMethod("HandleResponse").Invoke(theType, new object[] { message }); return "MessageHandler: " + messageType; That's all, folks! Update February 13, 2008: The code has now been tested in a very high throughput environment, and it performs read more...

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Managing Unmanaged Resources

submitted by animaonline 9 months, 18 days ago

softscenario.blogspot.com — Unmanaged Resources are objects that are not garbage collected, which means that they are not reclaimed by the system when the garbage collector cleans up after you. But are Unmanaged Resources resources outside .NET framework like DLL used through interop? No, unmanaged resources can also be database connection. It is a common mistake by programmers not to close the connection when finished working with it, in misconception that the garbage collection will close it. So how do I identify if the object is an unmanaged resource? If the object implement the IDisposable interface it have an unmanaged resource and you need to call the IDisposable.Dispose() method to clean the objects unmanaged resource. If you use the object in a single call you can wrap it in a using statement (http://softscenario.blogspot.com/2007/10/using-using.html), and it will call the Dispose() method for you. If you keep the object for a longer time you must support the IDisposable interface in your class, and in your implementation of the Idisposable.Dispose() call the member's IDisposable method. Remember to look for the IDisposable interface in the classes you use in your development. You will be surprised how many classes that do. read more...

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