C#

public class Student
{
    public int StudentId;
    public string StudentName;
    public int CourseId;
    public virtual Course Courses { get; set; }
}

public class Course
{
    public int CourseId;
    public string CourseName;
    public string Description;
    public ICollection<Student> Students {get;set;}
    public ICollection<Lecture> Lectures { get; set; }
}

public class Lecture
{
    public int LectureId;
    public string LectureName;
    public int CourseId;
    public virtual Course Courses { get; set; }
}

public ICollection<Student> Students {get;set;}
public ICollection<Lecture> Lectures { get; set; }

using Microsoft.VisualBasic;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;

public class Form1
{

	private void Form1_Load(System.Object sender, System.EventArgs e)
	{
		Timer1.Interval = 100;
		// timer to watch for foreground windows
		Timer1.Start();
	}

	private void Timer1_Tick(System.Object sender, System.EventArgs e)
	{
		dynamic hWnd = GetForegroundWindow();
		// get window handle of foreground window
		// a Win7 explorer window is in foreground.
		if (ClassName(hWnd) == "CabinetWClass") {
			Timer1.Stop();
			// stop this timer!
			using (Form2 f2 = new Form2()) {
				// show a popup window 
				f2.ShowDialog();
			}
		}
	}

	#region "API"
	[DllImport("user32.dll", CharSet = CharSet.Auto)]
	private static extern Int32 GetClassName(System.IntPtr hWnd, System.Text.StringBuilder lpClassName, Int32 nMaxCount);

	[DllImport("user32.dll", CharSet = CharSet.Auto)]
	private static extern IntPtr GetForegroundWindow();

	private string ClassName(IntPtr hWnd)
	{
		StringBuilder sb = new StringBuilder(256);
		GetClassName(hWnd, sb, 256);
		return sb.ToString;
	}
	public Form1()
	{
		Load += Form1_Load;
	}
	#endregion

}