Get back to my program with keyboard

Get back to my program with keyboard

• Buddhist

  You'd need to register a hotkey with Windows and have your form respond to it. .NET doesn't let you do it but you can use the necessary P/Invoke voodoo like this:
  
  Imports System.Runtime.InteropServices
  
  Public Class Form1
  '--- Windows API declarations
  Private Const WM_HOTKEY As Integer = &H312
  Private Const MOD_ALT As Integer = &H1
  Private Const MOD_CONTROL As Integer = &H2
  Private Const MOD_SHIFT As Integer = &H4
  Private Declare Function RegisterHotKey Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal id As Integer, ByVal fsModifier As Integer, ByVal vk As Integer) As Integer
  Private Declare Function UnregisterHotKey Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal id As Integer) As Boolean
  Private Declare Function SetForegroundWindow Lib "user32.dll" (ByVal hWnd As IntPtr) As Boolean
  
  Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
  RegisterHotKey(Me.Handle, 0, MOD_CONTROL + MOD_SHIFT, Keys.U)
  End Sub
  Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
  UnregisterHotKey(Me.Handle, 0)
  End Sub
  Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
  If (m.Msg = WM_HOTKEY AndAlso m.WParam = CType(0, IntPtr)) Then
  Me.Visible = True
  If Me.WindowState = FormWindowState.Minimized Then Me.WindowState = FormWindowState.Normal
  SetForegroundWindow(Me.Handle)
  End If
  MyBase.WndProc(m)
  End Sub
  End Class
  
  Note that I've made the hotkey Control + Shift + U, Alt + U would trigger too often.
  
  
  

• J. Wind

  nobugz,

  do you know by any chance how can I write the line that has the "user32.dll" reference in C#

  
  

• AxelJump

  nobugz,
  thank you so much, I was about to post my translation (I managed to translate your VB code to C#). But man, you're fast :)

  I had a problem though, whenever I call SetForgroundWindow I get an exception : Unable to find an entry point named 'SetForgroundWindow' in DLL 'user32.dll'. (Same exception for UnregisterHotkey).

  Anyway, I guess the problem somewhere in my translation, I'll copy and paste your C# code and try again.

  Many thanks again & kind regards

  
  

• Sureshpr

  There's more than one. I just wrote the full C# version, it is popular code:
  
  using System;
  using System.Windows.Forms;
  using System.Runtime.InteropServices;
  
  namespace WindowsApplication1 {
  public partial class Form1 : Form {
  private const int MYKEYID = 0; // In case you want to register more than one...
  public Form1() {
  InitializeComponent();
  RegisterHotKey(this.Handle, MYKEYID, MOD_CONTROL + MOD_SHIFT, Keys.U);
  this.FormClosing += Form1_FormClosing;
  }
  private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
  UnregisterHotKey(this.Handle, MYKEYID);
  }
  protected override void WndProc(ref Message m) {
  if (m.Msg == WM_HOTKEY && m.WParam.ToInt32() == MYKEYID) {
  this.Visible = true;
  if (this.WindowState == FormWindowState.Minimized)
  this.WindowState = FormWindowState.Normal;
  SetForegroundWindow(this.Handle);
  }
  base.WndProc(ref m);
  }
  // P/Invoke declarations
  private const int WM_HOTKEY = 0x312;
  private const int MOD_ALT = 1;
  private const int MOD_CONTROL = 2;
  private const int MOD_SHIFT = 4;
  [DllImport("user32.dll")]
  private static extern int RegisterHotKey(IntPtr hWnd, int id, int modifier, Keys vk);
  [DllImport("user32.dll")]
  private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
  [DllImport("user32.dll")]
  private static extern bool SetForegroundWindow(IntPtr hWnd);
  }
  }
  
  
  

• Prajakta Chavan

  Thanks guys,

  I have a friend that pointed me to this site which is what I need. I works like the old TSR programs, get the key - if it is what you need then process - forward the key back to windows.

  If anyone is interested the link is: http://www.developer.com/net/net/article.php/2193301

  Thanks again,

  Wayne

  
  
  

• senior man

  nobugz,

  The one I tried to use didn't work out. Yours did just what I wanted to do. Thanks.

  
  
  

• AaronL

  interesting. I'm unsure actually.

  your best bet is to store the application in the systray instead (right handside in the taskbar where all the icons are) and access it from that, as if the form was hidden, then you would not know how to access it, since it'll lose its focus.

  I guess the user could also access it by pressing the ALT+Tab keys to swtich to a different program, which yours will be in there since its in a process and actively running

  
  
  

• jkas

  Good pickup NoBugz

  I personally wouldnt register hotkeys with Windows for a number of reasons.

  1) the hotkey you assigned could change within say future version of Windows (unlikely)

  2) the hotkey maybe registered with perhaps another applications

  It is good that you unregister the hotkey just before you exit, good practice. But that was just my own personal opinion :-)

  
  
  
• Get back to my program with keyboard