Question

public class MyClass
{
    // private fields


    //////////////////////////////////////////////////////////////////////////
    public MyClass(string param1, string param2)
    {
        // do some stuff
    }

    private static object syncRoot = new Object();
    private static volatile MyClass instance = null;

    public static MyClass  Log
    {
        get
        {
            if (instance == null)
            {
                lock (syncRoot)
                {
                    if (instance == null)
                        instance = new MyClass();
                }
            }

            return instance;
        }
    }

    private MyClass()
    {
        // do some stuff
    }

    public void myFunction(string txt, uint flags)
    {
         // do some stuff
    }
}

This is my class and I use it this way

    MyClass.Log.myFunction("some string", flags);

But constantly get that either MyClass is null or MyClass.Log is null when i use this class in other class functions.

What do I do wrong?

In addition to the question here is the error i get:

 System.NullReferenceException: Object reference not set to an instance of an object.
   at MyNamespace.MyClass..ctor()
   at MyNamespace.MyClass.get_Log()

Answer 1

The code you showed looks good.
MyClass can’t be null as it is a class. Log shouldn’t be null either, your singleton implementation looks OK.

My guess is that the problem is that you are using the parameterless constructor of MyClass. I guess that myFunction somehow uses something that is only initialized in the constructor that takes the two parameters.

Actually, according to your stack trace the problem is inside the parameterless constructor. I guess you are trying to log something in there, like this : instance.Log(...);. That won’t work, because at that point instance is still null. You should simply use Log(...) instead.