In C#, the interface can be instantiated?

Question

I\'m reading the code in here. I find that private ITreeModel _model; in TreeList.cs:

namespace Aga.Controls.Tree
{
    public class TreeList: L         


        

Answer 1

You can never instantiate an interface in C# directly, but yes you can instantiate a subclass implementing that interface. For example:

interface IShape
{
   //Method Signature
   void area(int r);
}

public class Circle : IShape
{
   //method Implementation
   void area(int r)
   {
      float area;
      area = 3.14 * r * r;
      Console.WriteLine("The area of the circle is: {0}",area);
   }
}

public class Shapes
{
   public static void Main() {
      //Uncommenting the following line will cause compiler error as the  
      // line tries to create an instance of interface.
      // interface i = new IShape();

     // We can have references of interface type.
     IShape i = new Circle();
     i.area(10);
   }
}