What does this colon (:) mean?

Question

Before the this keyword is a colon. Can anyone explain what the colon means in this context? I don't believe this is inhertance.

Thanks

using System;

namespace LinkedListLibrary
{
    class ListNode
    {
        private object data;
        private ListNode next;

        public ListNode(object dataValue)
            : this(dataValue, null)
        {
        }

        public ListNode(object dataValue, ListNode nextNode)
        {
            data = dataValue;
            next = nextNode;
        }

        public ListNode Next
        {
            get
            {
                return next;
            }
            set
            {
                next = value;
            }
        }
        public object Data
        {
            get
            {
                return data;
            }
        }


    }
}

Answer 1

It (along with the this keyword) is instructing the constructor to call another constructor within the same type before it, itself executes.

Therefore:

public ListNode(object dataValue)
    : this(dataValue, null)
{
}

effectively becomes:

public ListNode(object dataValue)
{
    data = dataValue;
    next = null;
}

Note that you can use base instead of this to instruct the constructor to call a constructor in the base class.