I have an application that works based on the current client process.
I need to get the filename and its absolute path when opened. That is:

If for example the client opens the file “test.txt”, I need to get the path “c: project test.txt” instead of “c: windows system32 notepad.exe”. The same goes for .DOC, .XLS, etc …

The code snippet below returns the process-related information, which includes the software path (… notepad.exe).

[DllImport("user32.dll", EntryPoint = "GetForegroundWindow", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
public static extern int GetForegroundWindow();

[...]

public static string GetFilePathName()
{
    uint procId = 0;
    int hWnd = GetForegroundWindow();
    GetWindowThreadProcessId(hWnd, out procId);
    var proc = Process.GetProcessById((int)procId);
}

Through the class of the Process is it possible to acquire the path of the file being worked?

Is it possible to acquire the path of the file being worked through the Process class?

No. For this case, the approach needs to be another one, using a .NET class called FileSystemWatcher “. I will remove the example below :

m_starting_path.Text = "C:
watcher = new FileSystemWatcher();

//---------------------------------------------------------------
// Suponho que seja uma aplicação que tenha um botão
// Aqui ocorre o acionamento do FileSystemWatcher, que 
// funciona basicamente com eventos. 

private void MeuBotaoClick(object sender, System.EventArgs e)
{
    if (watcher.EnableRaisingEvents == true) {
        MessageBeep(100);
        return
    }

    watcher.Path         = m_starting_path.Text;
    watcher.Filter       = m_filter.Text;
    watcher.NotifyFilter = NotifyFilters.FileName |
                           NotifyFilters.Attributes |
                           NotifyFilters.LastAccess |
                           NotifyFilters.LastWrite |
                           NotifyFilters.Security |
                           NotifyFilters.Size;


    watcher.Changed += new FileSystemEventHandler(OnFileEvent);
    watcher.Created += new FileSystemEventHandler(OnFileEvent);
    watcher.Deleted += new FileSystemEventHandler(OnFileEvent);
    watcher.Renamed += new RenamedEventHandler(OnRenameEvent);
    watcher.IncludeSubdirectories = true;
    watcher.EnableRaisingEvents = true;
}

public void OnFileEvent(object source, FileSystemEventArgs fsea)
{
    // Aqui você verifica modificações no arquivo (source)
}

public void OnRenameEvent(Object source, RenamedEventArgs rea)
{
    // Aqui você verifica arquivos renomeados
}

To relate the process to the file, You can use one of the proposed solutions in this OS question .