This dialog is suitable for use with "Open" or "Save" menu items.
Most useful member methods for this class are actually in the Gtk::FileChooser base class.
File: examplewindow.h
#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H
#include <gtkmm.h>
class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();
protected:
  //Signal handlers:
  virtual void on_button_file_clicked();
  virtual void on_button_folder_clicked();
  //Child widgets:
  Gtk::VButtonBox m_ButtonBox;
  Gtk::Button m_Button_File, m_Button_Folder;
};
#endif //GTKMM_EXAMPLEWINDOW_H
File: examplewindow.cc
#include "examplewindow.h"
#include <iostream>
ExampleWindow::ExampleWindow()
: m_Button_File("Choose File"),
  m_Button_Folder("Choose Folder")
{
  set_title("Gtk::FileSelection example");
  add(m_ButtonBox);
  
  m_ButtonBox.pack_start(m_Button_File);
  m_Button_File.signal_clicked().connect( sigc::mem_fun(*this, &ExampleWindow::on_button_file_clicked) );
  m_ButtonBox.pack_start(m_Button_Folder);
  m_Button_Folder.signal_clicked().connect( sigc::mem_fun(*this, &ExampleWindow::on_button_folder_clicked) );
  show_all_children();
}
ExampleWindow::~ExampleWindow()
{
}
void ExampleWindow::on_button_folder_clicked()
{
  Gtk::FileChooserDialog dialog("Please choose a folder", Gtk::FILE_CHOOSER_ACTION_SELECT_FOLDER);
  dialog.set_transient_for(*this);
    
  //Add response buttons the the dialog:
  dialog.add_button(Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);
  dialog.add_button("Select", Gtk::RESPONSE_OK);
  
  int result = dialog.run();
  //Handle the response:
  switch(result)
  {
    case(Gtk::RESPONSE_OK):
    {
      std::cout << "Select clicked." << std::endl;
      std::cout << "Folder selected: " << dialog.get_filename() << std::endl;
      break;
    }
    case(Gtk::RESPONSE_CANCEL):
    {
      std::cout << "Cancel clicked." << std::endl;
      break;
    }
    default:
    {
      std::cout << "Unexpected button clicked." << std::endl;
      break;
    }
  }
}
void ExampleWindow::on_button_file_clicked()
{
  Gtk::FileChooserDialog dialog("Please choose a file", Gtk::FILE_CHOOSER_ACTION_OPEN);
  dialog.set_transient_for(*this);
  //Add response buttons the the dialog:
  dialog.add_button(Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);
  dialog.add_button(Gtk::Stock::OPEN, Gtk::RESPONSE_OK);
  //Add filters, so that only certain file types can be selected:
  Gtk::FileFilter filter_text;
  filter_text.set_name("Text files");
  filter_text.add_mime_type("text/plain");
  dialog.add_filter(filter_text);
  Gtk::FileFilter filter_cpp;
  filter_cpp.set_name("C/C++ files");
  filter_cpp.add_mime_type("text/x-c");
  filter_cpp.add_mime_type("text/x-c++");
  filter_cpp.add_mime_type("text/x-c-header");
  dialog.add_filter(filter_cpp);
  
  Gtk::FileFilter filter_any;
  filter_any.set_name("Any files");
  filter_any.add_pattern("*");
  dialog.add_filter(filter_any);
  //Show the dialog and wait for a user response:
  int result = dialog.run();
  //Handle the response:
  switch(result)
  {
    case(Gtk::RESPONSE_OK):
    {
      std::cout << "Open clicked." << std::endl;
      std::string filename = dialog.get_filename(); //Notice that it is a std::string, not a Glib::ustring.
      std::cout << "File selected: " <<  filename << std::endl;
      break;
    }
    case(Gtk::RESPONSE_CANCEL):
    {
      std::cout << "Cancel clicked." << std::endl;
      break;
    }
    default:
    {
      std::cout << "Unexpected button clicked." << std::endl;
      break;
    }
  }
  
}
File: main.cc
#include <gtkmm/main.h>
#include "examplewindow.h"
int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);
  ExampleWindow window;
  Gtk::Main::run(window); //Shows the window and returns when it is closed.
  return 0;
}