What will happen if you don't specify any constructor in your class and try to call the constructor in the client code? The answer is simple, that will work, C# will automatically call the invisible default constructor without parameters, (Unless you don't specify any private constructor in the class), the following code will work. class ClassA { public void DoAction( int Count) { Console .WriteLine( "Count: " + Count.ToString()); } } class Program { static void Main( string [] args) { ClassA ClsAObj1 = new ClassA (); } } The following code will not work: class ClassA { private ClassA() { } public void DoAction( int Count) { Console .WriteLine( "Count: " + Count.ToString()); } } class Program {