Application.LocalUserAppDataPath プロパティ

private MyApplicationContext() {
    formCount = 0;

    // Handle the ApplicationExit event to know when the application is exiting.
    Application.ApplicationExit += new EventHandler(this.OnApplicationExit);

    try {
        // Create a file that the application will store user specific data in.
        userData = new FileStream(Application.UserAppDataPath + "\\appdata.txt", FileMode.OpenOrCreate);

    } catch(IOException e) {
        // Inform the user that an error occurred.
        MessageBox.Show("An error occurred while attempting to show the application." + 
                        "The error is:" + e.ToString());

        // Exit the current thread instead of showing the windows.
        ExitThread();
    }

    // Create both application forms and handle the Closed event
    // to know when both forms are closed.
    form1 = new AppForm1();
    form1.Closed += new EventHandler(OnFormClosed);            
    form1.Closing += new CancelEventHandler(OnFormClosing);            
    formCount++;

    form2 = new AppForm2();
    form2.Closed += new EventHandler(OnFormClosed);            
    form2.Closing += new CancelEventHandler(OnFormClosing);            
    formCount++;

    // Get the form positions based upon the user specific data.
    if (ReadFormDataFromFile()) {
        // If the data was read from the file, set the form
        // positions manually.
        form1.StartPosition = FormStartPosition.Manual;
        form2.StartPosition = FormStartPosition.Manual;

        form1.Bounds = form1Position;
        form2.Bounds = form2Position;
    }

    // Show both forms.
    form1.Show();
    form2.Show();
}

private void OnApplicationExit(object sender, EventArgs e) {
    // When the application is exiting, write the application data to the
    // user file and close it.
    WriteFormDataToFile();

    try {
        // Ignore any errors that might occur while closing the file handle.
        userData.Close();
    } catch {}
}