static void Main(string[] args)
{
//allow to add new methods to existing types without modifying existing code
// this source code cannot be amended therefore we have to create another class that wraps this class
var result = new ThirdPartyMath();
Console.WriteLine(result.Add(4, 4));
//crteate a wrapper class to extended functionality
//ThirdPartyMathExtended result1;
//result1.obj.Add(2, 2); // a way of extedning the thirdparty DLL // using inheritiance / aggrgation - adding class to an existing class
//result1.Subtract(7, 4);
Console.WriteLine(result.Subtract(10, 5)); // after added extension to wrapper class i can include subtract
Console.ReadLine();
string testString = "Simon";
Console.WriteLine(testString.GetFirstLettter());
}
//public ThirdPartyMath obj = new ThirdPartyMath(); remove aggregation
public static int Subtract(this ThirdPartyMath obj, int num1, int num2)
{
return(num1 - num2);
}
