Option Explicit On
Option Strict On
 
Public Class Form1
 
    Private Declare Function ShowWindow Lib "user32.dll" (ByVal hwnd As Int32, _
                                                          ByVal nCmdShow As _
                                                          Int32) _
                                                          As Int32
    Private Const SW_HIDE As Int32 = 0
    Private Const SW_SHOW As Int32 = 5
    Private Const SW_SHOWNORMAL As Int32 = 1
    Private MainHandles As ArrayList = Nothing
 
    Private Function GetHandles(ByVal Name As String) As ArrayList
        Dim MainHandles As ArrayList
        Dim processes() As Process = _
          System.Diagnostics.Process.GetProcessesByName(Name)
        If Not processes Is Nothing AndAlso processes.Length > 0 Then
            MainHandles = New ArrayList
            For Each process As Process In processes
                MainHandles.Add(process.MainWindowHandle)
            Next
        Else
            Throw New Exception("sorry. cannot be found a process")
        End If
        Return MainHandles
    End Function
 
    Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        '// Hide
        Try
            Dim ProcessName As String = "Notepad"
            Me.MainHandles = Me.GetHandles(ProcessName)
            For Each handle As IntPtr In Me.MainHandles
                Debug.WriteLine("send hide message to " + handle.ToString() + _
                  "..")
                ShowWindow(handle.ToInt32, SW_HIDE)
            Next
            Debug.WriteLine("done")
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        '// Show
        Try
            If Me.MainHandles Is Nothing Then Return
            For Each handle As IntPtr In Me.MainHandles
                Debug.WriteLine("send show message to " + handle.ToString() + _
                  "..")
                ShowWindow(handle.ToInt32, SW_SHOWNORMAL)
            Next
            Debug.WriteLine("done")
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
    End Sub
End Class