How to figure out in C#, at runtime, whether an object of a class, implements an interface or not?

If a class implements an interface, there must be a way to find out at run time, whether the object of this class implements an interface or not. There are three ways to do this:

1) Explicit cast - A try catch block may be weaved in the C# code, to figure out whether a class supports an interface or not. This may be done by explicitly casting an object to the interface itself. See code below to understand how this works:

//Say we have an interface by the name IBooks

//Let there be a class by the name MathsBooks, which may or may not implement IBooks

//Lets find out using a try catch block, how we may figure this out...

MathsBooks mb = new MathsBooks();

IBooks ib;

try

{

   ib = (IBooks)mb; //Here, we are explicitly casting the object mb to IBooks

   Messagebox.Show("It works, MathsBooks does implement from IBooks");

}

catch(InvalidCastException ex)

{

  Messagebox.Show(ex.Message);

  Messagebox.Show("It doesn't work, MathsBooks does not implement from IBooks");

}

2) Using the "as" keyword - getting a reference to an interface

Using the "as" keyword to check whether an object supports an interface or not, is pretty simple. For this, an instance of the interface needs to be set to the class's object, which is internally casted to the interface using the "is" keyword. See code example below for more clarity:

MathsBooks mb = new MathsBooks();

IBooks ib = mb as IBooks;

if(ib == null)

{

  Messagebox.Show("The class MathsBooks does not implement the interface IBooks");

}

else

{ Messagebox.Show("The class MathsBooks does implement the interface IBooks");}

2) Using the "is" keyword - getting a reference to an interface

This is perhaps, the simplest way to check for an interface reference. If an interface is being implemented by an object of a class, the "is" keyword may be used. This may be checked in combination with an if statement. See code example below:

MathsBooks mb = MathsBooks();

if(mb is IBooks)

{

   Messagebox.Show("The class MathsBooks does implement the interface IBooks");}

}