Posts

out, ref and InvokeMember !!!

When I was working on the .NET reflection extravaganza thing that I explained in my previous column, i learnt one another interesting thing, that is about the Type.InvokeMember. How will pass out or ref parameters for the method invoked using Type.InvokeMember ? If you are going to invoke a method with the prototype

int DoSomething(string someString, int someInt);

then you would use InvokeMember like this:-

object obj = someType.InvokeMember(“DoSomething”,
        BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance,
        null,
        this,
        new object[] {“Largest Integer”, 1});

or use some variables in the new object[] {…}. But what do you with the args if DoSomething takes out or ref parameters ?

.NET Reflection Extravanganza !!!

Over the past few weeks, I have been involved with this module that got the best of both worlds - .NET and I, 😁.

Ok, this was the problem. We have a COM server, let us name it Server. I had to write an assembly in C#, let us call it Bridge, that will listen to all of the events fired by the Server and perform an action Action. To keep that Action simple, let us assume we have to log them to the database. But the Server fires hundreds of events, and it is not wise to write up static event handlers for all of them. Also, if more events are (ever) added in the future, the Bridge should be able to support it without code changes.

The twist in the game was that this was a brown + green field development project. That demanded a wise solution - learn from the past and better the future.

Where is my C++ ?

I have been using C# for quite some time now, and that too VS 2005. I see that Programming Pain at a macro level has boiled down to thinking than coding. Though it might be an advantage on one side, I feel I have become lazy. Since I am a programmer from the C++ world, it was very easy to become lazy. The small and handy applications that I write for myself in C++, I am writing them in C#. Even now I am a great disciple of C++. And even though C++/CLI is out there, and I work a small amount of it in my project, I am getting inclined to C#. More ...

Infinite .NET Languages !!!

Though I knew that there are quite a few languages for the .NET platform, I came to know when surfing today that there are many well beyond my knowledge, most surprisingly like the COBOL.

Check it out @ http://www.dotnetpowered.com/languages.aspx

Implementing COM OutOfProc Servers in C# .NET !!!

Had to implement our COM OOP Server project in .NET, and I found this solution from the internet after a great deal of search, but unfortunately the whole idea was ruled out, and we wrapped it as a .NET assembly. This is worth knowing.

Step 1

Implement IClassFactory in a class in .NET. Use the following definition for IClassFactory.

namespace COM
{
   static class Guids
   {
      public const string IClassFactory = "00000001-0000-0000-C000-000000000046";
      public const string IUnknown = "00000000-0000-0000-C000-000000000046";
   }

   ///
   /// IClassFactory declaration
   ///
   [ComImport(), InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid(COM.Guids.IClassFactory)]
   internal interface IClassFactory
   {
      [PreserveSig]
      int CreateInstance(IntPtr pUnkOuter, ref Guid riid, out IntPtr ppvObject);
      [PreserveSig]
      int LockServer(bool fLock);
   }
}

Step 2

Non-conventional Window Shapes [I love C#] !!!

I am not a UI guy. More specifically, I love to work with UIs. I think (only) a UI can give a better picture of the system in a multitasking environment unlike Unix. I do not say I hate Unix. And I do not like to work on UIs ie program on UIs cuz I do not know much. But have always wanted to create a non-conventional window, say an elliptical one. .NET made things like that very easy for guys like me. Look at the code below for creating a ellipitcal window. More ...

Serialization and Exceptions !!!

I am just like Alice in Wonderland, and not yet got out of the wonders of the .NET framework, C# and the VS 2003(5) IDE. I thought that the serialization is all not my thing until I do something big in C#. I had written this custom exception class in my project that has 3 processes connected by .NET Remoting Infrastructure. I throw my custom exception for a scenario but all I got was some other exception: More ...

Know where you initialize and Do not forget to uninitialize !!!

If you have long been programming in C++/COM and then you move to C#.NET, the first difference you can feel is that you got a ctor for the object you create unlike the CoCreateInstance. In the C++/COM world, you generally would have a Initialize method to do the construction sort of, paired with Terminate/Uninitialize method. Similar is the case with singleton classes. For singleton classes in C++, you will have public static Instance or GetInstance method to get the only and one instance of the class and then use the initialize method to do the construction. This is certainly advantageous than the ctor facility in .NET, since you will not know when the instance will be initialized without the initialize method. Any call like SingletonClass.GetInstance().SomeMethod may initialize the singleton anywhere and you will not exactly do the initialization during the application startup, which in many cases will lead to application errors after startup. More ...

An encounter with Hashtables !!!

I encountered a situation like this where I had a hashtable in which the key is a string and the value is some object, and I had to change the values of all the keys [from zero to count] to null or some other value. I used the some of the facilities – enumerator, the Keys property etc provided by the hash table itself but it did not work out, and I spent too much time on this. More ...

A Note On Finalize !!!

This is not about what Finalize is, but well Finalize is the last call on a managed object, where you can perform some clean up operations, before getting garbage collected by the .NET runtime. A few important things that are to be noted about finalizers are:-

• In C#, finalizers are represented by the ~ClassName [destructor syntax], and the Object.finalize can neither be overridden or called directly. It cannot be called directly because it is protected. The destructors in C# also take care of calling the dtor of the base class.
• Finalizer is called on an object only once, just before the .NET runtime attempts to garbage collect the object.
• Finalizers can be called anytime on a managed object that is not being referenced, and on any thread by the .NET runtime.
• The order in which the finalizers are called is also not fixed. Even when two objects are related to each other in some way, there is no hierarchial order in which the finalizers for the objects will be called.
• During an application shutdown, finalizers will be called even on objects that are still accessible.

The most interesting part of the finalizer is not when it is called but when all is it NOT called. This is where we need to watch and rely on the Dipose method IDispoable - Dispose pattern¹.