2.3 Using a Component

only for RuBoard

Now that you have a component, you need a way to use it. Example 2-2 contains a listing for a simple client. Save it to a file named hello-client.vb . Let's see how everything fits together, and then you can compile it.

Example 2-2. "Hello, world" client

 Imports System Imports Greeting     Public Class Application       Public Shared Sub Main( )     Dim hw As New Hello( )     hw.Write("World")     Console.ReadLine( )   End Sub     End Class 

The Greeting namespace defined in Example 2-1 was imported. Without it, every class in the Greeting namespace would have to be referenced directly, as in the following code:

 Public Shared Sub Main( )  Dim hw As New Greeting.Hello( )  hw.Write("World") End Sub 

All standalone executables require an entry point with this signature:

 Public Shared Sub Main( ) 

This is where everything begins, but as you can see, not much is going on. The only thing the client does is declare an instance of the Hello class (which is defined in the component) and call its Write method.

When compiled, Example 2-2 must explicitly reference hello.dll for everything to compile. This can be accomplished with the /r compiler option. Assuming that the DLL lives in the same directory as the client code, this executable can be compiled as follows :

 C:\>vbc /t:exe /r:hello.dll hello-client.vb 

This compilation produces an executable named hello-client.exe . You can change the name of the output file by using the /out compiler option:

 C:\>vbc /t:exe /r:hello.dll /out:hello.exe hello-client.vb 

When the executable runs, the following code is dumped to the console:

 Hello, World! 

only for RuBoard