Struct Pointer Initialization in C#

Question

unsafe public class Temp
{
    public struct Node
    {
        Node *left;
        Node *right;
        int value;
    }

    public Temp()
    {
        Node* T=new Node();
        T->left=null;
        T->right=null;
        T->value=10;
    }
}

main()
{
    Temp temp=new Temp();
}

It gives error that Object reference not set to instance of an object. How can I do it when I want to make AVL Tree Program(which I have created and tested in C++ but copying in C# gives error)

Answer 1

Don't try to use pointers in C# like this. If you are porting C++ code that uses pointers as references, instead use reference types. Your code will not work at all; "new" does not allocate structs off the heap, for one thing, and even if it did pointers are required to be pinned in place in C#; C# is a garbage-collected language.

In short never use unsafe unless you thoroughly understand everything there is to know about memory management in C#. You are turning off the safety system that is there to protect you, and so you have to know what that safety system does.

The code should be:

public class Temp // safe, not unsafe
{
    public class Node // class, not struct
    {
        public Node Left { get; set; } // properties, not fields
        public Node Right { get; set; } 
        public int Value { get; set; }
    }

    public Temp()
    {
        Node node = new Node();
        node.Left = null; // member access dots, not pointer-access arrows
        node.Right = null;
        node.Value = 10;
    }
}

Answer 2

The problem is with the line:

Node* T=new Node();

In C#, new Node() returns Node (which is reference), not Node* (which is pointer). You should use stackalloc, instead.

Anyway, please do not copy C++ and do it C# way!