.NET Remoting over TCP

Remoting in .NET is quite similar to RMI in Java. To begin with, we need an object that has the methods we would be executing on the server-side. This object inherits from MarshalByRefObject. This indicates that the client does not get a copy of the object but rather a reference to the remote object. We then have a hosting process and a client process.

In our example, the hosting process creates a new instance of the TcpChannel class (pass the TCP port number to the constructor of TcpChannel for the server hosting process) and registers the object using ChannelServices.RegisterChannel. Then, the class we are hosting has to be registered using the RemotingConfiguration.RegisterWellKnownServiceType method - it takes the type of our class as the first parameter, the registration name as the second parameter and the object mode (singleton & single call modes) as the third parameter. When creating a console application, we would usually add a Console.ReadLine statement at the end of the application to prevent it from exiting.

The client application would create and register an instance of TcpChannel. Then, obtain an instance of the class hosted on the server using Activator.GetObject - with the type of the class as the first parameter and the URL (Example: tcp://localhost:8080/my_service) as the second parameter. You can now call methods on the object as you would for a normal object.

Type Forwarding

Type Forwarding enables client applications to refer to a library at compile time for a type that is later moved to another library.

Example:
using System.Runtime.CompilerServices;
[assembly:TypeForwardedTo(typeof(DestinationLib.TheType))]

The IFormattable interface

Implementing the IFormattable interface let's you do much more with the ToString() method if you're developing text-based applications or are trying to create strings out of object fields.

To implement the IFormattable interface, you have to create a ToString method that accepts a format string and an IFormatProvider object. The IFormatProvider object isn't relevant but the format string can be used, such as to return only one field of an object. Here's a sample implementation:

class TimeInterval : IFormattable {

...

public override string ToString() {
return ToString(null, null);
}

public string ToString (string format, IFormatProvider formatProvider) {
if (format == null) {
return this.Hour.ToString() + ":" + this.Minute.ToString();
} else if (format == "h") {
return this.Hour.ToString();
} else if (format == "m") {
return this.Minute.ToString();
} else throw new Exception("Invalid format specified");
}
}

To use the new method, you could provide a format string to either string.Format or Console.WriteLine. Example:
TimeInterval timeInterval = new TimeInterval();
Console.WriteLine("{0:h} hours and {0:m} minutes", timeInterval);
Console.WriteLine("{0,2:h}:{0,2:m}", timeInterval); //the ",2" specifies the minimum number of characters in the resulting string - if positive, the output is left-padded, otherwise it is right-padded

Common Interfaces

The following are some common interfaces implemented by user-defined types:

IComparable: This is required for sorting.

IDisposable: This is used for manually disposing an object

IConvertible: This provides conversion to a base type

ICloneable: This is to provide a copy for an object

IEquatable: This is used when comparison of objects using "==" is required

IFormattable: This is used to convert an object into a formatted string (rather than use the base ToString method)

Group chat coming soon in GoogleTalk

Google has a GoogleTalk gadget web client accessible from it's website at http://www.google.com/talk . It features Group chat but the downside is that it doesn't receive offline messages. As a friend from the old country would say, you've got to pick what suits the moment.

If it's any indicate of what's to come, we should see Group Chat in the GoogleTalk client sometime soon.

RSS vs Atom

RSS and Atom are both used to publish news feeds (summarized content used by readers to track content changes). Both are quite popular, although RSS has received more attention than Atom. RSS is a specification by the Harvard University, whereas Atom is an RFC by the IETF and IESG.

I read a pretty interesting comparison of the two at:
http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared

VB 7 vs VB 8: Operator Overloading

When designing .NET as a programming platform, the designers could either leave out operator overloading, as Java does, or they could continue the tradition started off by C and continued by C++ to provide greater control to the programmer. They chose to let the programmer decide which path to take and so added the feature into the framework, but for some reason didn't provide a way to use it through Visual Basic .NET 2003 (VB 7).

In .NET 1.1, VB 7 did not include the concept of operator overloading. You could neither define nor use overloaded operators and the workaround was to create methods, such as a .Add(object) method. C#, however, did include operator overloading even on .NET 1.1.

.NET 2.0 introduced the Operator keyword in Visual Basic, a feature in VB 8, which reduces the amount of code and provides added convenience for the developers.