Methods

• A method is a member function in a class.

• Access modifier are used to control access.

Regular Methods

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }

    public void PrintDetails()
    {
        if (ValidateData())
        {
            Console.WriteLine("ID: {0}, Name: {1}", Id, Name);
        }
        else
        {
            Console.WriteLine("ERROR");
        }
    }

    private bool ValidateData()
    {
        if (Id <= 0 || string.IsNullOrEmpty(Name))
        {
            return false;
        }
        else
        {
            return true;
        }
    }
}

Constructors

• A constructor is a special type of a member method.

• The method identifier (name) must be identical to the class name.

• A constructor cannot have a return type, and can contain zero or more parameters.

  • The constructor with no parameters is called the default constructor, and is called at the time of object creation.

• Typically used for initializing member variables of a class instance, and to perform other important work that must be done up front.

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }

    public Person()
    {
        Id = -1;
        Name = string.Empty;
    }
}

static void Main(string[] args)
{
    // Default constructor is called at this point
    var person = new Person();
}

• A class may contain more than one constructor.

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }

    public Person()
    {
        Id = -1;
        Name = string.Empty;
    }

    public Person(int id, string name)
    {
        Id = id;
        Name = name;
    }
}

• Below is a meaningful example of a class and usage of constructors.

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }

    public Person()
    {
        Id = -1;
        Name = string.Empty;
    }

    public Person(int id, string name)
    {
        if (ValidateData(id, name))
        {
            Id = id;
            Name = name;
        }
    }

    public void PrintDetails()
    {
        if (ValidateData(Id, Name))
        {
            Console.WriteLine("ID: {0}, Name: {1}", Id, Name);
        }
        else
        {
            Console.WriteLine("ERROR");
        }
    }

    private bool ValidateData(int id, string name)
    {
        if (id <= 0 || string.IsNullOrEmpty(name))
        {
            return false;
        }
        else
        {
            return true;
        }

        // This function is also a good use case for the Conditional Operator:
        // return (id <= 0 || string.IsNullOrEmpty(name)) ? false : true;
    }
}