using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml;
using System.IO;

public partial class Gallery : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        if (!Page.IsPostBack)
        {
            if (ViewState["ArrayData"] == null)
            {
                var filePaths = Directory.GetFiles(Server.MapPath("/gallery/Rotate/")).Select(f => Path.GetFileName(f));
                //Store Array in a ViewState 
                ViewState["ArrayData"] = filePaths.ToArray();
            }
        }
        else
            LoadRandomImages();
    }

    private void LoadRandomImages()
    {
        
        //Retrieve Array value in the ViewState back to the array variable 
        string[] filePaths = (string[])ViewState["ArrayData"];
        Random rnd = new Random();
        int pos = rnd.Next(0, filePaths.Length);
        imgRotating.Src = "/gallery/Rotate/"+filePaths[pos];

    }
}