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EnumWindows (user32)
 
.
Summary

C# Signature:

[DllImport("user32.dll")]
static extern bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);

User-Defined Types:

None.

VB.NET Signature:

Public Declare Function EnumWindows Lib "user32" ( _

       ByVal lpEnumFunc As CallBack, _
       ByVal lParam As IntPtr) As Boolean

User-Defined Types:

Public Delegate Function CallBack( _

   ByVal hwnd As IntPtr, _
   ByVal lParam As IntPtr) As Boolean

Tips & Tricks:

Please add some!

C# SAMPLE CODE

public delegate bool CallBackPtr(int hwnd, int lParam);

public class EnumReport

    {
    [DllImport("user32.dll")]
    public static extern int EnumWindows(CallBackPtr callPtr, int lPar);

    public static bool Report(int hwnd, int lParam)
        {
        Console.Write("Window handle is "+hwnd);
        return true;
        }
    }

void Main()

    {
    CallBackPtr callBackPtr = new CallBackPtr(EnumReport.Report);
    EnumReport.EnumWindows(callBackPtr, 0);
    }

VB.NET SAMPLE CODE

Imports System.Runtime.InteropServices

Public Class Form1

    Inherits System.Windows.Forms.Form

#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)
    If disposing Then
        If Not (components Is Nothing) Then
        components.Dispose()
        End If
    End If
    MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    '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.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
    components = New System.ComponentModel.Container
    Me.Text = "Form1"
    End Sub

#End Region

    Public Delegate Function CallBack( _
       ByVal hwnd As IntPtr, _
       ByVal lParam As IntPtr) As Boolean

    Public Declare Function EnumWindows Lib "user32" ( _
       ByVal lpEnumFunc As CallBack, _
       ByVal lParam As IntPtr) As Boolean

    Public Function getAllWindowHandles() As ArrayList

    Dim arlWindowHandlesList As New ArrayList
    Dim gch As GCHandle = GCHandle.Alloc(arlWindowHandlesList)

    Try
        EnumWindows(AddressOf ReceiveAllWindowHandles, GCHandle.op_Explicit(gch))
    Finally
        gch.Free()
    End Try

    Return arlWindowHandlesList

    End Function

    Private Function ReceiveAllWindowHandles( _
    ByVal hwnd As IntPtr, _
    ByVal lParam As IntPtr) As Boolean

    Dim gchTemp As GCHandle = GCHandle.op_Explicit(lParam)
    Dim arlWindowHandlesList As ArrayList = DirectCast(gchTemp.Target, ArrayList)

    arlWindowHandlesList.Add(hwnd)

    Return True

    End Function

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load

    Dim cboHandles As ComboBox = New ComboBox
    Dim arlHandles As ArrayList = getAllWindowHandles()

    Me.Controls.Add(cboHandles)
    cboHandles.Location = New Point(20, 20)
    cboHandles.DataSource = arlHandles

    End Sub

End Class

Alternative Managed API:

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Documentation
EnumWindows on MSDN

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