The most powerful feature of Web Parts is their ability to work together. Instead of trying to solve a particular problem in one big complicated Web Part, you can break the problem down into several smaller parts and then connect them. By Connected Web Parts, we mean that they are communicating with one another. For example, it is common for one Web Part to allow for the search and selection of information, such as a customer, and it then enables the information to be communicated to another Web Part that shows the customer details for the customer that was selected. In this case, normally something such as the Customer ID is communicated, and the second Web Part will be responsible for looking up the customer details using this information.
Our communication will done by creating a custom interface. An interface, in .NET, is the definition of a class without the implementation. In our case, it is a contract for explicitly specifying the data that will be exchanged...