static void Main(string[] args)
{
string value = "dot net perls";
value = value.UppercaseFirstLetter();
ExtensionMethodsCustom obj = new ExtensionMethodsCustom();
obj.Test1();
obj.Test2();
obj.Test3();
int a = 10.MultiplyBy(2);
Console.WriteLine(a);
Console.ReadKey();
}
public static void Test3(this ExtensionMethodsCustom obj)
{
Console.WriteLine("i am test3");
}