using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //GenerateButtons();
        //if (!IsPostBack)
        //{            
        //    GenerateRandom();
        //}        
    }
    protected void Page_Init(object sender, EventArgs e)
    {
        GenerateButtons();
        GenerateRandom();
    }
    private void GenerateButtons()
    {
        for (int i = 0; i < 16; i++)
        {
            short j = ((short)i);
            j += 1;
            Button b = new Button();
            b.Width = 80;
            b.Height = 80;
            b.Text = (i + 1).ToString();
            b.TabIndex = j;
            b.ID = "Button" + (i + 1).ToString();
            //b.OnClientClick = "Swap";
            b.Click += new EventHandler(Swap);
            Panel1.Controls.Add(b);
        }
        Button bEmpty = (Button)Panel1.FindControl("Button16");
        bEmpty.Text = "";
    }
    protected void GenerateRandom()
    {
        int arr_Numbers = new int; // array to prevent duplicate numbers
        Random r = new Random();
        bool boolFlag = true;
        int i = 0;
        int randNum = 0;
        String bID = null;   // the button ID (etc. "Button11")
        String bText = null; // the Text field on each button (etc. "11")
        Button tmpButton = null; // pointer to a button
        while (i <= 14)
        {
            while (boolFlag == true)
            {
                randNum = r.Next(15);
                if (arr_Numbers != 1)
                {
                    arr_Numbers = 1;
                    boolFlag = false;
                }
            }
            bID = "Button" + (i + 1).ToString(); // "Button1".."Button15"
            bText = (randNum + 1).ToString(); // "1".."16"
            tmpButton = (Button)Panel1.FindControl(bID); //temporary pointer to the button ID
            tmpButton.Text = bText; // change the text value of the button im pointing at
            boolFlag = true;
            i++;
        }
    }
    protected void Swap(object sender, EventArgs e)
    {
        int myTabIndex = ((Button)sender).TabIndex; //between 1-16
        Button current = ((Button)sender);
        String left = "Button" + (myTabIndex - 1).ToString();
        String right = "Button" + (myTabIndex + 1).ToString();
        String up = "Button" + (myTabIndex - 4).ToString();
        String down = "Button" + (myTabIndex + 4).ToString();
        Button bLeft = (Button)Panel1.FindControl(left);
        Button bRight = (Button)Panel1.FindControl(right);
        Button bUp = (Button)Panel1.FindControl(up);
        Button bDown = (Button)Panel1.FindControl(down);
        if ((bLeft != null) && (bLeft.Text == "") && ((current.TabIndex % 4) != 1))
        {
            String swapX = current.Text;
            String swapY = bLeft.Text;
            current.Text = swapY;
            bLeft.Text = swapX;
            return;
        }
        if ((bRight != null) && (bRight.Text == "") && ((current.TabIndex % 4) != 0))
        {
            String swapX = current.Text;
            String swapY = bRight.Text;
            current.Text = swapY;
            bRight.Text = swapX;
            return;
        }
        if ((bUp != null) && (bUp.Text == ""))
        {
            String swapX = current.Text;
            String swapY = bUp.Text;
            current.Text = swapY;
            bUp.Text = swapX;
            return;
        }
        if ((bDown != null) && (bDown.Text == ""))
        {
            String swapX = current.Text;
            String swapY = bDown.Text;
            current.Text = swapY;
            bDown.Text = swapX;
            return;
        }
    }
}