Heap Sort in C#

public static void HeapSort(int[] input)
{
    //Build-Max-Heap
    int heapSize = input.Length;
    for (int p = (heapSize - 1) / 2; p >= 0; p--)
        MaxHeapify(input, heapSize, p);

    for (int i = input.Length - 1; i > 0; i--)
    {
        //Swap
        int temp = input[i];
        input[i] = input[0];
        input[0] = temp;

        heapSize--;
        MaxHeapify(input, heapSize, 0);
    }
}

private static void MaxHeapify(int[] input, int heapSize, int index)
{
    int left = (index + 1) * 2 - 1;
    int right = (index + 1) * 2;
    int largest = 0;

    if (left < heapSize && input[left] > input[index])
        largest = left;
    else
        largest = index;

    if (right < heapSize && input[right] > input[largest])
        largest = right;

    if (largest != index)
    {
        int temp = input[index];
        input[index] = input[largest];
        input[largest] = temp;

        MaxHeapify(input, heapSize, largest);
    }
}