Invoking Unmanaged DLL Functions from Compact Framework for Pocket PC

In this example we will use the Compact Framework to create a program containing a launch pad for the Pocket PC. Our program will provide an integrated interface to launch some of the common programs on the Pocket PC. This sample serves to demonstrate the use of the Pinvoke mechanism on the Pocket PC to launch external programs such as Internet Explorer and Calculator. This example can be extended to create a convenient toolbox for launching frequently used Pocket PC programs.

The Compact Framework does not have complete support for COM Interop and interoperating with ActiveX controls. It provides the Platform Invoke mechanism for calling unmanaged DLLs. We will explore this functionality more in detail in this example.

The complete code listing along with sample screenshots follow.

The core of our example consists of using C# 's DLLImport attribute to access the "CreateProcess" function from the unmanaged DLL coredll.dll. This function is invoked in the program to launch the program as specified in the parameters.



Figure: Launchpad Application in Action



Figure: PocketPc.com site opened from the LaunchPad program through a single button click

Complete Code Listing

Imports System
Imports System.Drawing
Imports System.Collections
Imports System.Windows.Forms
Imports System.Data
Imports System.Runtime.InteropServices
Public Class Form1
Inherits System.Windows.Forms.Form
Private button1 As System.Windows.Forms.Button
Private button3 As System.Windows.Forms.Button
Private button2 As System.Windows.Forms.Button
Private button4 As System.Windows.Forms.Button
Private button5 As System.Windows.Forms.Button
Private mainMenu1 As System.Windows.Forms.MainMenu
#Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'This call is required by the Windows Form Designer.
InitializeComponent()
'Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
MyBase.Dispose(disposing)
End Sub
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Private Sub InitializeComponent()
Me.mainMenu1 = New System.Windows.Forms.MainMenu
Me.button1 = New System.Windows.Forms.Button
Me.button3 = New System.Windows.Forms.Button
Me.button2 = New System.Windows.Forms.Button
Me.button4 = New System.Windows.Forms.Button
Me.button5 = New System.Windows.Forms.Button
'button1
Me.button1.Location = New System.Drawing.Point(40, 16)
Me.button1.Size = New System.Drawing.Size(96, 32)
Me.button1.Text = "PocketPc.Com"
AddHandler button1.Click, AddressOf button1_Click
'button3
Me.button3.Location = New System.Drawing.Point(40, 64)
Me.button3.Size = New System.Drawing.Size(96, 32)
Me.button3.Text = "IE"
AddHandler button3.Click, AddressOf button3_Click
'button2
Me.button2.Location = New System.Drawing.Point(40, 112)
Me.button2.Size = New System.Drawing.Size(96, 32)
Me.button2.Text = "Calculator"
AddHandler button2.Click, AddressOf button2_Click
'button4
Me.button4.Location = New System.Drawing.Point(40, 160)
Me.button4.Size = New System.Drawing.Size(96, 32)
Me.button4.Text = "Calendar"
AddHandler button4.Click, AddressOf button4_Click
'button5
Me.button5.Location = New System.Drawing.Point(40, 208)
Me.button5.Size = New System.Drawing.Size(96, 32)
Me.button5.Text = "Tasks"
AddHandler button5.Click, AddressOf button5_Click
'Form1
Me.Controls.Add(Me.button5)
Me.Controls.Add(Me.button4)
Me.Controls.Add(Me.button2)
Me.Controls.Add(Me.button3)
Me.Controls.Add(Me.button1)
Me.Menu = Me.mainMenu1
Me.Text = "Form1"
End Sub
Shared Sub Main()
Application.Run(New Form1)
End Sub 'Main
#End Region
Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
ShowPPCWebSite()
End Sub
Private Sub button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
StartCalc()
End Sub
Private Sub button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
StartIE()
End Sub
Private Sub button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
StartCalendar()
End Sub
Private Sub button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
StartTasks()
End Sub
Private Declare Function CreateProcess Lib "coredll.Dll" (ByVal strImageName As String, ByVal strCmdLine As String, ByVal pProcessAttributes As IntPtr, ByVal pThreadAttributes As IntPtr, ByVal bInheritsHandle As Integer, ByVal dwCreationFlags As Integer, ByVal pEnvironment As IntPtr, ByVal pCurrentDir As IntPtr, ByVal bArray() As [Byte], ByVal oProc As ProcessInfo) As Integer
Private Sub ShowPPCWebSite()
Dim pi As New ProcessInfo
CreateProcess("iexplore.exe", "www.microsoft.com/mobile/pocketpc/default.asp", IntPtr.Zero, IntPtr.Zero, 0, 0, IntPtr.Zero, IntPtr.Zero, New [Byte](128) {}, pi)
End Sub 'ShowPPCWebSite
Private Sub StartIE()
Dim pi As New ProcessInfo
CreateProcess("iexplore.exe", "", IntPtr.Zero, IntPtr.Zero, 0, 0, IntPtr.Zero, IntPtr.Zero, New [Byte](128) {}, pi)
End Sub 'StartIE
Private Sub StartCalc()
Dim pi As New ProcessInfo
CreateProcess("calc.exe", "", IntPtr.Zero, IntPtr.Zero, 0, 0, IntPtr.Zero, IntPtr.Zero, New [Byte](128) {}, pi)
End Sub 'StartCalc
Private Sub StartCalendar()
Dim pi As New ProcessInfo
CreateProcess("calendar.exe", "", IntPtr.Zero, IntPtr.Zero, 0, 0, IntPtr.Zero, IntPtr.Zero, New [Byte](128) {}, pi)
End Sub 'StartCalendar
Private Sub StartTasks()
Dim pi As New ProcessInfo
CreateProcess("tasks.exe", "", IntPtr.Zero, IntPtr.Zero, 0, 0, IntPtr.Zero, IntPtr.Zero, New [Byte](128) {}, pi)
End Sub 'StartTasks
End Class
Public Class ProcessInfo
Public Process As Integer
Public Thread As Integer
Public ProcessID As Integer
Public ThreadID As Integer
End Class 'ProcessInfo

NOTE:

This article is purely for demonstration. This article should not be construed as a best practices white paper. This article is entirely original, unless specified. Any resemblance to other material is an un-intentional coincidence and should not be misconstrued as malicious, slanderous, or any anything else hereof.

Conclusion:

In this article, we explored the code to launch external applications on Pocket PC using Pinvoke and unmanaged DLLs. I would like to give credit to Scott Swigart for his valuable inputs on support newsgroups.