i need to close a specific child window

Question

Within my program, I have identified a process via System.Diagnostics.Processand.GetProcesses.  Now I need to close one and only one of its windows whose window title i know.  How do I do that?

Answer 1

VB.NET does not have methods for doing this (well, maybe you could do it with the System.Windows.Automation library, but few people are familiar with it).

The way I would do this is by using P/Invoke on the applicable Windows system APIs.  Unfortunately, if you are not familiar with the windows APIs, you are going to wonder how I ever figured this out...

Option Explicit On
Option Strict On

Imports System.ComponentModel
Imports System.Runtime.InteropServices
Imports System.Text

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim wc As New WindowCloser
        Dim p As Process = Process.GetProcessesByName("ExeNameWithoutExeExtension")(0)
        wc.CloseWindow(p, "Exact Title of Window in Process")
    End Sub

End Class

Public Class WindowCloser

    Private m_ProcessIdToFind As Integer
    Private m_TitleToFind As String
    Private m_TopLevelWindowsInProcess As New List(Of IntPtr)
    Private m_MatchingWindowsInProcess As New List(Of IntPtr)

    Public Sub CloseWindow(ByVal proc As Process, ByVal title As String)
        m_ProcessIdToFind = proc.Id
        m_TitleToFind = title
        m_TopLevelWindowsInProcess.Clear()
        m_MatchingWindowsInProcess.Clear()

        If Not EnumWindows(AddressOf EnumWindowsImpl, IntPtr.Zero) Then
            Throw New Win32Exception
        End If
        For Each hwnd As IntPtr In m_TopLevelWindowsInProcess
            EnumChildWindows(hwnd, AddressOf EnumChildWindowsImpl, IntPtr.Zero)
        Next hwnd
        For Each hwnd As IntPtr In m_MatchingWindowsInProcess
            SendMessage(hwnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero)
        Next hwnd
    End Sub

    Private Function EnumWindowsImpl(ByVal hwnd As IntPtr, ByVal lParam As IntPtr) As Boolean
        Dim processId As Integer = 0
        GetWindowThreadProcessId(hwnd, processId)
        If processId = m_ProcessIdToFind Then
            m_TopLevelWindowsInProcess.Add(hwnd)
            CheckWindow(hwnd)
        End If
        Return True
    End Function

    Private Function EnumChildWindowsImpl(ByVal hwnd As IntPtr, ByVal lParam As IntPtr) As Boolean
        CheckWindow(hwnd)
        Return True
    End Function

    Private Function CheckWindow(ByVal hwnd As IntPtr) As Boolean
        Dim sb As New StringBuilder(255)
        If GetWindowText(hwnd, sb, sb.Capacity) <> 0 Then
            If sb.ToString() = m_TitleToFind Then
                m_MatchingWindowsInProcess.Add(hwnd)
            End If
        End If
    End Function

    <DllImport("user32.dll")> _
    Private Shared Function GetWindowThreadProcessId(ByVal hWnd As IntPtr, <Out()> ByRef lpdwProcessId As Integer) As Integer
    End Function

    <DllImport("user32.dll", SetLastError:=True)> _
    Private Shared Function EnumWindows(ByVal lpEnumFunc As EnumWindowsProc, ByVal lParam As IntPtr) As <MarshalAs(System.Runtime.InteropServices.UnmanagedType.Bool)> Boolean
    End Function

    <DllImport("user32.dll")> _
    Private Shared Function EnumChildWindows(ByVal hWndParent As IntPtr, ByVal lpEnumFunc As EnumWindowsProc, ByVal lParam As IntPtr) As <MarshalAs(System.Runtime.InteropServices.UnmanagedType.Bool)> Boolean
    End Function

    Private Delegate Function EnumWindowsProc(ByVal hwnd As IntPtr, ByVal lParam As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean

    <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
    Private Shared Function GetWindowText(ByVal hWnd As IntPtr, ByVal lpString As StringBuilder, ByVal cch As Integer) As Integer
    End Function

    Private Const WM_CLOSE As Integer = 16

    <DllImport("user32.dll")> _
    Private Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr
    End Function

End Class

Answer 2

Within my program, I have identified a process via System.Diagnostics.Processand.GetProcesses.  Now I need to close one and only one of its windows whose window title i know.  How do I do that?

You'll need to modify the following code so that it will close the correct form (replace form_to_close with the known title of the window you want to close):

    Dim wdw As Form

    For Each wdw In My.Application.OpenForms
        If wdw.Text = "form_to_close" Then
            wdw.Close()
            Exit Sub
        End If
    Next

:)

---

Doug

SEARCH ... then ask

Answer 3

Thanks Doug.  A couple of problems.  The child window that I need to close belongs to an external app.  So, I need to traverse that app's children.

The other problem, is that we have moved to c#.

Thanks again,

gus

Answer 4

Hi YiChun,

It looks like the code will do the trick.  Unfortunately we have moved to c#.  Would you have equivalent code in c#?

Thanks,

gus

Answer 5

Hi YiChun,

It looks like the code will do the trick.  Unfortunately we have moved to c#.  Would you have equivalent code in c#?

Thanks,

gus

You can convert the code to C# at http://www.carlosag.net/Tools/CodeTranslator/

kaymaf

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If that what you want, take it. If not, ignored it and no complain

Answer 6

Hi Barillas,

Thank you for your reply.

You also can try: http://www.developerfusion.com/tools/convert/vb-to-csharp/ to convert VB.NET code to C#.

Hope this helps. If you have any concern, please feel free to let me know.

Best regards,
Yichun Chen

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Answer 7

Kaymaf,

I used YiChun's translator and it works pretty well.  However, I wanted to compare it with yours, but the link seems to be broken.  Did it get moved?

Gus