MainPage.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace Heapsort
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
        }

        void up(int []t, int L)
        {
	        int temp;
	        int index = L;

	        while (index > 0)
	        {
		        int parent = (index - 1) / 2;
		        if ( t[parent] > t[index] )
		        {
			        temp = t[parent];
			        t[parent] = t[index];
			        t[index] = temp;
			        index = parent;
		        }
		        else break;
	        }
        }

        void makeInput(int x, int []t, ref int L)
        {
	        t[L] = x;
	        up(t, L);
	        L++;
        }
	
        void down(int []t, int L)
        {
	        int i = 0;
	        while(true)
	        {
		        int p = 2 * i + 1;		// left descendant of the root i
		        if ( p > L )
			        break;
		        if ( p + 1 <= L )
			        if ( t[p] > t[p+1] )
				        p++;
		        if ( t[i] < t[p] )
			        break;
		        int temp = t[p];
		        t[p] = t[i];
		        t[i] = temp;
		        i = p;
	        }
        }

        int takeRoot(int []t, ref int L)
        {
	        int x = t[0];
	        L--;
	        t[0] = t[L];
	        down(t, L);
	        return x;
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            int i;

            string[] stringArray = string1.Text.Split(' ');
            int lenghtArray = stringArray.Length;
            resultstring.Text = Convert.ToString(lenghtArray);

            int[] numberArray;
            numberArray = new int[lenghtArray];

            for (i = 0; i < lenghtArray; i++)
            {
                numberArray[i] = Convert.ToInt32(stringArray[i]);
            }

	        int L = 0;
            int[] t = new int[lenghtArray];

            for (i = 0; i < lenghtArray; i++)
                makeInput(numberArray[i], t, ref L);

            for (i = 0; i < lenghtArray; i++)
                numberArray[i] = takeRoot(t, ref L);
	
            string result = "";
            for (i = 0; i < lenghtArray; i++)
            {
                result += (Convert.ToString(numberArray[i])) + " ";
            }

            resultstring.Text = result;
        }
    }
}