c# - Why does my FormLoad event handler call the custom class' default constructor instead of the one with arguments? -

i making basic multiclass gui program assignment have created 3 custom classes inherit form abstract class (readingmaterial) , interface. problem running when run information should passed each class's constructor (i've included class online example) not being passed , classes calling default constructor instead, gui components showing zeros , blank spaces instead of populating other information passed constructors. why isn't calling correct constructor instead of default?

(gui form partial class)

public partial class presentationgui : form {     private book book;     private magazine magazine;     private online online;      public presentationgui()     {         initializecomponent();     }      private void rdbtnonline_checkedchanged(object sender, eventargs e)     {         txtbxpagecount.text = online.pagecount.tostring();         txtbxtitle.text = online.title;         txtbxauthor.text = online.author;         txtbxurl.text = online.websiteurl;         txtbxprintable.text = online.hardcopyavailability();          // ...     }      private void presentationgui_load(object sender, eventargs e)     {         book = new book(1000, "c# programming", "barbara doyle",             "cengage", "5th edition");          online = new online(5, "c sharp (programming language)", "crowd sourced author",                 "https://en.wikipedia.org/wiki/c_sharp_(programming_language)");          magazine = new magazine(200, "pc magazine", "varied authors",                 "ziff davis", 6, 16);     } } 

(online class inherits readingmaterial abstract class(below))

public class online : readingmaterial, iprintable {     private string websiteurl;     public string websiteurl { get; set; }      public online()         :base()     {         websiteurl = "";     }      public online(int pagecount, string title, string author, string url)         :base(pagecount, title, author)     {         websiteurl = url;     }      public string hardcopyavailability()     {         return "printable";     } } 

(base class readingmaterial)

public abstract class readingmaterial {     private int pagecount;     private string title;     private string author;      public int pagecount { get; set; }     public string title { get; set; }     public string author { get; set; }      public readingmaterial()     {         pagecount = 0;         title = "";         author = "";     }      public readingmaterial(int pagecount, string title, string author)     {         this.pagecount = pagecount;         this.title = title;         this.author = author;     } } 

it not constructor problem. not connecting backing variables properties. either this:

public abstract class readingmaterial {     private string title;     public string title     {          { return title; }         set { title = value; }     }      ... } 

or drop backing variables , use automatically implemented properties. if so, c# automatically creates hidden backing variable you.

public string title { get; set; } 

and in constructor, assign parameter property instead of backing variable.

this.title = title;