Question

I study C# and I’m trying to understand the overloaded constructor, how it works and the point using them like a chain call? Why just not have only one constructor with all necessary parameters? Below I have some helping code for a task I’m working with, and I need some help to understand the point with all this constructors. Preciate some help! Thanks!

    public class Email
{
    //private email
    private string m_personal;
    //work mail
    private string m_work;

    public Email()
    {
    }

    public Email(string workMail) : this(workMail, string.Empty)
    {
    }

    public Email(string workMail, string personalMail)
    {
        m_work = workMail;
        m_personal = personalMail;
    }

    public string Personal
    {
        //private mail
        get { return m_personal; }

        set { m_personal = value; }
    }

    public string Work
    {
        get { return m_work; }

        set { m_work = value; }
    }

    public string GetToStringItemsHeadings
    {
        get { return string.Format("{0,-20} {1, -20}", "Office Email", "Private Email"); }
    }

    public override string ToString()
    {
        string strOut = string.Format("{0,-20} {1, -20}", m_work, m_personal);
        return strOut;
    }


}

Answer 1

Why just not have only one constructor with all necessary parameters?

What if users of your class are only interested in some parameters? Using your example, what if somebody doesn’t have personal email? Should they pass null or string.Empty? This kind of type-level knowledge is best handled by type itself.

By exposing extra constructor with work email only, you’re essentially telling your class consumers “Don’t have personal email? Don’t worry, I will handle it”.

On top of that, chaining definitions naturally helps to avoid code redundancy.