// If you want to see the counter increase for every hit on the page, please change the check
// in page_load from the session object to the page.ispostback. Read more about the firefox bug that made me
// change the logic in this way below.
// Warning!!! For some obscure reason, the pageload event is firing twice in Firefox. More about that
// here: http://stackoverflow.com/questions/2153579/page-load-fires-twice-on-firefox. Despite my efforts (disabling
// all firefox extensions for example), the event is still firing twice and the img tag that is generated by ASP
// does not have the common error of missing an img attribute. So, in firefox, every reload of the page causes
// the counter used to increase by 2 if I used PostBack to check if the user is new. Therefore I enabled
// a session variable that checks if the user is already counted. That means that simple reload of the page
// will not increase the counter. You have to use a different browser or close the current one and open the page
// again to increase it. Bear in mind that if you stopped the server, the counter will be reset (I have implemented
// this functionality via Global.asax Application_Start event.
protected void Page_Load(object sender, EventArgs e)
{
var context = new DataContext();
var data = context.Data.SingleOrDefault();
if (data == null)
{
var visitorData = new VisitorData();
visitorData.Number++;
context.Data.Add(visitorData);
context.SaveChanges();
return;
}
if (Session["Catched"] == null) //(!Page.IsPostBack)
{
Session["Catched"] = "catched";
data.Number++;
context.SaveChanges();
}
context.Dispose();
Response.Clear();
GetImage();
}
protected void Application_Start(object sender, EventArgs e)
{
var context = new DataContext();
var data = context.Data.SingleOrDefault();
if (data == null)
{
var visitorData = new VisitorData();
context.Data.Add(visitorData);
context.SaveChanges();
return;
}
else
{
data.Number = 0;
context.SaveChanges();
}
}
private void GetImage()
{
Bitmap generatedImage = new Bitmap(200, 200);
using (generatedImage)
{
Graphics gr = Graphics.FromImage(generatedImage);
using (gr)
{
gr.FillRectangle(Brushes.MediumSeaGreen, 0, 0, 200, 200);
var context = new DataContext();
var data = context.Data.SingleOrDefault();
gr.DrawString("Number of users: " + data.Number,
new Font("Arial", 14, FontStyle.Regular), SystemBrushes.WindowText, new PointF(10, 40));
Response.ContentType = "image/gif";
generatedImage.Save(Response.OutputStream, ImageFormat.Gif);
}
}
}