Skip to main content

Explicit Interface Implementation !!!

I have encountered this [wait i'll explain] sort of situation many times and I mostly do this way in C++.

Assume you have a class CMyClass that exposes its functionality through its public methods, and also let it listen to events from some sources, events being OnSomeEvent or OnXXXX(), by implementing some event interface IXModuleEvents. Now these event listener methods are reserved only for internal use and are not meant to be called by the users. So when I implement the IXModuleEvents interface in CMyClass, I make them private. Think about it and the problem is solved. It is the polymorphism game, that never cares for the accessibility of the method.

But I was in the same situation and my head had stopped working and my hands went coding the same way, and found that it does not work. In C#, i have the facility to declare a interface and by default its methods are public, strictly no need of any access specifiers. And the class that implements has to implement it publicly. So my OnXXX() methods get exposed.

But yes, there is a solution for the situtation, it is called Explicit Interface Implementation. It is this way:-

internal interface IXModuleEvents
{
void OnSomeEvent(int i, int j);
void OnSomeOtherEvent(string name);
}

public class CMyClass : IXModuleEvents
{
// ..... Other implementation

// No need of any access specifiers
void IXModuleEvents.OnSomeEvent(int i, int j)
{
}

// No need of any access specifiers
void IXModuleEvents.OnSomeOtherEvent(string name)
{
}
}
So you can access these OnXXXX() method implementation only if you have a IXModuleEvents reference of the CMyClass, and try out with a CMyClass reference to access the event listener method implementation.

Comments

Popular posts from this blog

Extension Methods - A Polished C++ Feature !!!

Extension Method is an excellent feature in C# 3.0. It is a mechanism by which new methods can be exposed from an existing type (interface or class) without directly adding the method to the type. Why do we need extension methods anyway ? Ok, that is the big story of lamba and LINQ. But from a conceptual standpoint, the extension methods establish a mechanism to extend the public interface of a type. The compiler is smart enough to make the method a part of the public interface of the type. Yeah, that is what it does, and the intellisense is very cool in making us believe that. It is cleaner and easier (for the library developers and for us programmers even) to add extra functionality (methods) not provided in the type. That is the intent. And we know that was exercised extravagantly in LINQ. The IEnumerable was extended with a whole lot set of methods to aid the LINQ design. Remember the Where, Select etc methods on IEnumerable. An example code snippet is worth a thousand ...

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: [DllImport("ole32.dll")] private static extern int CoR...

Android meets .NET !!!

It is always fun for me to program in C# (besides C++). If so, how would I feel if I was able to program for Android in C#? You may be wondering what in the world I am talking about. Android development environment is all Java and open source stuff. How could this Microsoft thing fit onto it? Well, it seems that some clever guys had huddled up and ported Mono for Android , developed .NET libraries for the Android SDK, and also supplemented it with a 'Mono for Android' project template in Visual Studio; and called it mono for android . Thus we end up writing C# code happily for Android. After a bunch of installations , fire up your Visual Studio (2010) and you should be seeing a new project template 'Mono for Android' under C#. Create a new 'Mono for Android' project, which by default comes with an activity - C# code. Modified the orginal code to try starting a new activity from the default one... The project layout for most of the part is...