Class and Objects

Question

I have a class named as SAMPLE with empty constructor. Note: Constructor is a  PRIVATE  Now in another class if i need to create the instance and to initialize the the SAMPLE class am getting Inaccessible due to its protection level. I know the error occurs because constructor is private if i change the constructor to Public i will not have any issue. But I should not change the SAMPLE class. Now is there any way to create instance for SAMPLE class and to initialize that ? Please help me.. Thanks in advance.

Vulpes · Answer

Normally I'd expect a singleton class with a private constructor to have a public static 'factory' method to instantiate it or to get a reference to the existing instance. However failing that you can still instantiate it using reflection. Here's an example: using System; using System.Reflection; class Sample { // private static Sample mc; /* typical factory method public static Sample GetInstance(int i string s) { if (mc == null) { mc = new Sample(i s); } return mc; } */ private Sample(int i string s) { MyInt = i; MyString = s; } public int MyInt { get; private set; } public string MyString { get; private set; } } class Program { static void Main() { Type t = typeof(Sample); BindingFlags bf = BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.CreateInstance; Type[] paramTypes = {typeof(int) typeof(string)}; ConstructorInfo ci = t.GetConstructor(bf null paramTypes null); object[] paramValues = {42 The answer to everything}; Sample mc = (Sample)ci.Invoke(paramValues); Console.WriteLine({0} {1} mc.MyInt mc.MyString); Console.ReadKey(); } } The output as expected is: 42 The answer to everything

Jayakumar · Answer

Thanks a lot Vulpes. It's working fine.

Jayakumar · Answer

Thanks for your reply Prasham :) I have gone through that link already. My case is i should not make change in the SAMPLE class. But as per that link i need to create a singleton pattern in SAMPLE class. I need a way to solve my problem with the changes in invoking class.

Prasham Sabadra · Answer

Hi Please have a look once following links: http://www.dotnetperls.com/private-constructor