How to allowed a class to be inherited

hi,
 try.... method it self sealed.
 public class test1
  {
  public sealed void notoverride()
  {
  }
  public virtual void fnoverride()
  {
  }
  }
  public class test2 : test1
  {
  public override void fnoverride()
  {
  base.fnoverride();
  }
  }

All classes (except static classes) can be inherited from unless you mark them with the 'sealed' keyword:

public sealed class MyClass  // can't inherit from this class
{
    // code
}

If a child class contains a method which overrides a virtual method in its base class, you can prevent further overriding by descendants of the child class by marking the method as 'sealed'.