c# - Explanation needed: virtual, override and base -

why doesn't ", second id: " string in o.w2() printed out? know d2 property empty.

using system;  public class o {     public string f { get; set; }     public string l { get; set; }     public string d { get; set; }      public virtual string w()     {         return this.w2();     }      public virtual string w2()     {         return string.format("first name : {0}, last name: {1}, id: {2}", f, l, d);     } }  public class s : o {     public string d2 { get; set; }      public override string w()     {         return base.w2();     }      public override string w2()     {         return base.w2() + string.format(", second id: {0}", this.d2);     } }  class program {     static void main(string[] args)     {         o o = new s();          o.d = "12345678";         o.f = "john";         o.l = "jones";          console.writeline(o.w());          // output: first name : john, last name: jones, id: 12345678     } } 

because called override w() in turn calls base.w2(). inside class, base.w2() determined statically (at compile time) 1 in base class:

public override string w() {     // directly calls w2() base class, ignores override     return base.w2();  } 

if want polymorphism scenario, should omit base , call w2():

public override string w() {     // goes override     return w2();  }