Focus Windows Explorer From C# App In Task Bar

Question

Our company has application that runs as a task bar icon - there is no UI besides the task bar icon.

Certain events cause the task bar to launch a explorer.exe to show a directory. User interaction does not cause this, so our application does not have focus.

I am able to show the directory in windows explorer using code like this:

Process.Start("explorer.exe", "c:\somedirectory");

The problem is, the folder launches in the background and I can't seem to give it focus.

Part of the problem is that the explorer.exe process exits immediately, launching the explorer.exe process separately. I am able to find the launched window using Process.processes() and looking at the window title and start time of the process.

Once I finally get a handle on the process (and wait for it to open), I'm trying to focus it. Here's what I've tried:

//trying to bring the application to the front
form.TopMost = true;
form.Activate();
form.BringToFront();
form.Focus();

Process process = ...;

ShowWindow(process.Handle, WindowShowStyle.ShowNormal);
SetForegroundWindow(process.Handle);
SwitchToThisWindow(process.Handle, true);  

ShowWindow(process.MainWindowHandle, WindowShowStyle.ShowNormal);
SetForegroundWindow(process.MainWindowHandle);
SwitchToThisWindow(process.MainWindowHandle, true);  

This makes the window blink in the task bar, but it still isn't focused.

How can I get the window to come to the front of the screen?

Answer 1

You could use the Shell.Application scripting interface to ask Explorer to create and show a new window. I believe this is also possible using a typed interface, but the exact one escapes me at the moment.

var shellApplication = Type.GetTypeFromProgID("Shell.Application");
dynamic shell = Activator.CreateInstance(shellApplication);
shell.Open(@"C:\drop\");

This seems open the window with focus (Tested on Win 8.1 using a timer which opens after 30 seconds, then navigating around in a focused web browser until the timer fires).

Answer 2

To focus explorer.exe, the application itself needed focus. WinForms intentionally makes this difficult since it could be abused.

Here's how you can steal focus in WinForms. Keep in mind that it may have bad consequences.

Once your application has focus, you can focus another process:

[DllImport("user32.dll")]
private static extern bool SetForegroundWindow(IntPtr hWnd);

SetForegroundWindow(otherProcess.MainWindowHandle);

Here's how I found the explorer process. Like I said, the explorer.exe seems to launch another process and close, so the best option seemed to be to find the most recently launched explorer.exe process:

public static Process GetExplorerProcess()
{
    var all = Process.GetProcessesByName("explorer");
    Process process = null;
    foreach (var p in all)
        if (process == null || p.StartTime > process.StartTime)
            process = p;
    return process;
}

Another option that wouldn't require stealing focus is to show a message from your tray icon. Then you can setup a click handler to open/focus the folder. The application would naturally have focus from the click.

trayIcon.ShowBalloonTip(3000, "", msg, ToolTipIcon.Info);

This falls more in line with "don't annoy the user" but in my case the user is far more annoyed at having to click the bubble.

Update

Finding the explorer process requires admin privileges for your app. I've found that if you focus your own application first, then launch the folder, then the folder is automatically focused. In other words, there is no need to search through the current processes and call SetForegroundWindow.