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We have been using Windows APIs to get the most out of the Windows operating system. Sites like www.vbapi.com have always been my favorite hangouts for understanding and using APIs.
.NET extends its support for using Windows APIs. Let's check out how we can use the MessageBox API to display a simple MessageBox.
We will be using the DLLImport attribute for Platform Invoke (Pinvoke) service, which is used to tell the runtime that the code being executed is unmanaged code.
Imports system Imports System.Runtime.InteropServices PublicClass TestAPI SharedSub main() ' Display a messagebox using the Win32 API API.MessageBox(0, "API Message Box", "Win32 API", 0) EndSub EndClass 'Class that will expose the Win32 API PublicClass API ' Declare the external Win32 API function ' BETA 2 requires the <DLLimport> attribute before the function signature. <DLLimport("user32.dll")>PublicSharedFunction MessageBox(ByVal HwndAsInteger, _ ByVal [text]AsString, _ ByVal CaptionAsString, _ ByVal ypeAsInteger)AsInteger EndFunction EndClass
Compile the class as Vbc testapi.vb /r:system.dll. When we execute the testapi.exe we will see a MessageBox being popped up.
This was first published in May 2003