Making the application on top of all other applications

I have VB code as below which is used in call-center for emergency incoming calls to answer or reject. Which is working to put my application on top of all other application in a basic usage.

But, when user using PowerPoint in presentatoin full-screen mode and my application is trying to go on top it, it fails to do so.

  Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Me.TopMost = True
  end sub 

How do i tell my application even there is any power-point like fullscreen mode applications running put my application on top. Because its emergency incoming call popup.

If you look for "always on top" you will not find a flawless solution.

An alternative solution could be hidde all windows (even PP fullscreen presentation mode) like WinKey+D and restore your app call-center window (or show a notify icon) on incoming call.

using System.Threading;
using System;

namespace callCenterApp
{
  internal class Program
  {
    [STAThread]
    private static void Main(string[] args)
    {
      showDesktop();
    }

    private static void showDesktop()
    {
      Shell32.ShellClass objShel = new Shell32.ShellClass();
      objShel.ToggleDesktop();

      Thread.Sleep(1000);

      var notification = new System.Windows.Forms.NotifyIcon()
      {
        Visible = true,
        Icon = System.Drawing.SystemIcons.Warning,
        BalloonTipText = "Incomming emergency call",
        BalloonTipTitle = "Alert!",
        BalloonTipIcon = System.Windows.Forms.ToolTipIcon.Warning
      };
      notification.ShowBalloonTip(5000);
      Thread.Sleep(10000);
      notification.Dispose();
    }
  }
}

Import Microsoft Shell Controls And Automation COM (windows/SysWoW64/shell32.dll) to work with shell.

VB.NET version:

Namespace callCenterApp
    Friend Class Program
        <STAThread> _
        Private Shared Sub Main(args As String())
            showDesktop()
        End Sub

        Private Shared Sub showDesktop()
            Dim objShel As New Shell32.ShellClass()
            objShel.ToggleDesktop()

            Thread.Sleep(1000)

            Dim notification As New System.Windows.Forms.NotifyIcon() With { _
                .Visible = True, _
                .Icon = System.Drawing.SystemIcons.Warning, _
                .BalloonTipText = "Incomming emergency call", _
                .BalloonTipTitle = "Alert!", _
                .BalloonTipIcon = System.Windows.Forms.ToolTipIcon.Warning _
            }
            notification.ShowBalloonTip(5000)
            Thread.Sleep(10000)
            notification.Dispose()
        End Sub
    End Class
End Namespace