初学者请教：方法名前带"~"的表示什么意思？

有如下例子：
using System;namespace StaticTest
{
    class Employee
    {
        private string firstName;
        private string lastName;
        private static int count;   //Employee objects in memory        //constructor increments static Employee count
        public Employee(string fName, string lName)
        {
            firstName = fName;
            lastName = lName;            ++count;            Console.WriteLine("Employee object constructor: " + firstName + " " + lastName + "; count = " + Count);
        }        //destructor decrements static Employee count
        ~Employee()
        {
            --count;            Console.WriteLine("Employee object destructor: " + firstName + " " + lastName + "; count =" + Count);
        }        //FirstName property
        public string FirstName
        {
            get
            {
                return firstName;
            }
        }        //LastName property
        public string LastName
        {
            get
            {
                return lastName;
            }
        }        //static Count property
        public static int Count
        {
            get
            {
                return count;
            }
        }
    }
}
using System;namespace StaticTest
{
    class StaticTest
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Employee before instantiation: " + Employee.Count + "\n");            //create two Employees
            Employee employee1 = new Employee("Susan", "Baker");
            Employee employee2=new Employee("Bob","Jones");            Console.WriteLine("\nEmployees after instantiation: Employee.Count = " + Employee.Count + "\n");            //display the Employees
            Console.WriteLine("Employee 1: " + employee1.FirstName + " " + employee1.LastName + "\nEmployee 2: " + employee2.FirstName + " " + employee2.LastName + "\n");            //remove references to objects to indicate that objects can be garbage collected
            employee1 = null;
            employee2 = null;            //force garbage collection
            System.GC.Collect();            //wait until collection completes
            System.GC.WaitForPendingFinalizers();            Console.WriteLine("\nEmployees after garbage collection: " + Employee.Count);
        }
    }
}
输出：Employee before instantiation: 0Employee object constructor: Susan Baker; count = 1
Employee object constructor: Bob Jones; count = 2Employees after instantiation: Employee.Count = 2Employee 1: Susan Baker
Employee 2: Bob JonesEmployee object destructor: Bob Jones; count =1
Employee object destructor: Susan Baker; count =0Employees after garbage collection: 0
请按任意键继续. . .
请指教其中~Employee()方法起什么作用？