using System;

public class Program

{

    public static void Main()

    {

        IGenerateReport _IGenerateReport = new HtmlReport();

        if(_IGenerateReport is HtmlReport){}

        IGenerateReport _HtmlReport = _IGenerateReport as IGenerateReport;

    }

}

public interface IGenerateReport{

    public void GenerateReport();   

}

​

public class HtmlReport : IGenerateReport{

    public void GenerateReport(){}

}

​

public class JsonReport : IGenerateReport{

    public void GenerateReport(){}

}

​