Static Methods

• A static method in a non-static class can be accessed without an instance of that class.

• Consider the following two classes; Person and Pet.

  • Both a person and a pet has a birthday, so calculating the age is a common task.

  • However, the same method would need to be replicated in both classes as follows.

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public DateTime DOB { get; set; }

    public void PrintInfo()
    {
        Console.WriteLine("{0} {1}, Age: {2}", FirstName, LastName, GetAge());
    }

    public string GetAge()
    {
        var age = DateTime.Today.Year - DOB.Year;
        return string.Format("{0} years", age);
    }
}

public class Pet
{
    public string Name { get; set; }
    public DateTime DOB { get; set; }

    public void PrintInfo()
    {
        Console.WriteLine("{0}, Age: {1}", Name, GetAge());
    }

    public string GetAge()
    {
        var age = DateTime.Today.Year - DOB.Year;
        return string.Format("{0} years", age);
    }
}

• However, if the GetAge() method was marked as static in one of the classes, the other class could use the same method without having to create an instance of that class.

• In that case, however, that method won't be able to access the member variable of the class, and will need to be passed as a parameter.

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public DateTime DOB { get; set; }

    public void PrintInfo()
    {
        Console.WriteLine("{0} {1}, Age: {2}", FirstName, LastName, GetAge(DOB));
    }

    public static string GetAge(DateTime dob)
    {
        var age = DateTime.Today.Year - dob.Year;
        return string.Format("{0} years", age);
    }
}

public class Pet
{
    public string Name { get; set; }
    public DateTime DOB { get; set; }

    public void PrintInfo()
    {
        Console.WriteLine("{0}, Age: {1}", Name, Person.GetAge(DOB));
    }
}