Question

i can not read this line of code

public Wine (decimal price, int year) : this (price) { Year = year; }

what :this keyword do in a constructor

public class Wine
{
    public decimal Price;
    public int Year;

    public Wine (decimal price) 
    { 
        Price = price; 
    }

    public Wine (decimal price, int year) : this (price) 
    { 
        Year = year; 
    }
}

Answer 1

This is called constructor chaining. Instead of rewriting the code of the one-argument constructor, you simply call it. C# makes this simple by using this short notation with the colon.