Class and Objects

Jayakumar Balasubramaniam

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.

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes11y ago
Accepted 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 Balasubramaniam11y ago
Thanks a lot Vulpes. It's working fine.
Jayakumar Balasubramaniam11y ago
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 Sabadra11y ago
Hi,

Please have a look once following links:

http://www.dotnetperls.com/private-constructor