Microsoft 9GD00001 manual Reviewing the OnConnection Method, Understanding OnConnection Parameters

384Microsoft Visual Studio 2010: A Beginner’s Guide

Reviewing the OnConnection Method

As you learned earlier, the Connect class implements various interface methods so that VS can call into those methods to run your Add-In. One of the primary methods is OnConnection, which is a member of the IDTExtensibility2 interface. VS calls OnConnection when the Add-In loads. When calling OnConnection, VS passes four parameters that you can use to initialize the Add-In. The Add-In Project Wizard, covered in a previous section of this chapter, generates much skeleton code that uses parameter values in OnConnection to initialize the Add-In. While the example in this chapter doesn’t modify the OnConnection method, understanding the code is helpful in learning how the Add-In initializes and how it does affect the code you will write later. We’ll first take another look at OnConnection parameters and then examine the generated code.

Understanding OnConnection Parameters

The OnConnection method has four parameters. Each of the parameters are passed to the OnConnection method by VS; these parameters provide all of the information necessary for initializing the Add-In. Table 13-3 lists each parameter and its purpose.

Member

Type

Purpose

application	Compile-time type is Object, but	Application is the parent object for the entire VS
	the runtime type is defined by the	automation model. You use this to access all of the
	version you’re at. For example,	windows, commands, and other parts of the IDE.
	on older versions of VS, the
	runtime type of Application was
	DTE, but the runtime type of
	Application in VS 2010 is DTE2.
connectMode	Enum of type ext_ConnectMode	Read this parameter to figure out when and how
		the Add-In was loaded. In a following section,
		you’ll see how the OnConnection method reads this
		value to figure out when the Add-In loads for the
		first time.
addInInst	The compile-time type is Object,	This refers to the Add-In itself, allowing you to
	but runtime type is AddIn.	inspect various properties of the Add-In.
custom	Array	These aren’t used in the current example, but
		consider the fact that we’re implementing an
		interface. Besides VS 2010, you could have
		another application (host) that supported Add-Ins
		that implement the IDTExtensibility2 interface. Those
		hosts could use the custom array parameter to pass
		information specific to that application. Therefore,
		custom is another extensibility point to make the
		IDTExtensibility2 interface more flexible.

Table 13-3 OnConnection Method Parameters