Question

I created a Windows Forms application. I want to get the processing form (current form) in that application from another application. Because the (first) application consists of multiple forms, I want to know which form is processing/active.

Answer 1

GetForegroundWindow function

Retrieves a handle to the foreground window (the window with which the user is currently working).

C# Signature:

/// <summary>The GetForegroundWindow function returns a handle to the foreground window.</summary>
[DllImport("user32.dll")]
private static extern IntPtr GetForegroundWindow();

and s sample code from pinvoke:

public ApplicationState AppState
{
    get
    {
        Process[] processCollection = Process.GetProcessesByName(ProcessName);
        if(processCollection != null && processCollection.Length  >= 1 && 
            processCollection[0] != null)
        {
            IntPtr activeWindowHandle = Win32.GetForegroundWindow();
            //Optional int ProcessID;
            //Optional Win32.GetWindowThreadProcessId(GetForegroundWindow(),out ProcessID)
            foreach(Process wordProcess in processCollection)
            {
                //Optional if( ProcessID == wordProcess.Id ) return ApplicationState.Focused;
                if(wordProcess.MainWindowHandle == activeWindowHandle)
                {
                    return ApplicationState.Focused;
                }
            }
            return ApplicationState.Running;
        }
        return ApplicationState.NotRunning;
    }
}