Heap Sort in C#

using System;
public static class HeapSort {

public static void Sort(int[] arr) {
    int size = arr.Length;
    // Heapify
    for(int i = size / 2 - 1; i >= 0; i--) 
       {
        Heapify(arr, size, i);
    }
    
    int j = size - 1;
    while (j >= 1) 
       {
        // Swap the first with arr[i]. 
        Swap(arr, 0, j);
        // Heapify the array again.
        Heapify(arr, j, 0);
        // Then decrement i.
        j--;
    }
}

private static void Heapify(int[] arr, int size, int i) 
   {    
    int largest = i;
    // i-th element's left child.
    int leftLeaf = 2*i + 1;
    // i-th element's right child.
    int rightLeaf = 2*i + 2;
    
    // If the left child is larger than the current largest.
    if (leftLeaf < size && arr[leftLeaf] > arr[largest]) 
       {
        largest = leftLeaf;
    }
    // If the right child is larger than the current largest.
    if (rightLeaf < size && arr[rightLeaf] > arr[largest]) 
       {
        largest = rightLeaf;
    }
    
    // If the largest of the two is not the original largest
    if (largest != i) 
       {
        // Swap i and the largest.
        Swap(arr, i, largest);
        // Heapify the sub-tree. 
        Heapify(arr, size, largest); 
    }
}

private static void Swap(int[] arr, int a, int b) 
   {
    int tmp = arr[a];
    arr[a]  = arr[b];
    arr[b] = tmp;
}

}