How can I use my own random captcha in ASP.NET? - asp.net

Question

For hands on experience, I am generating random numbers and compare their sums on submission, but every time, I press button, random numbers are changing, How can I stop happening this? I considered different experiments, but not able to do that.
Here is my class code for random numbers:
public class Captcha
{
int num1, num2, total;
public int N1
{
get
{
return num1;
}
}
public int N2
{
get
{
return num2;
}
}
public int Total
{
get
{
return total;
}
}
Random r = new Random();
public Captcha()
{
Random r = new Random();
num1 = r.Next(1, 11) * 10;
num2 = r.Next(1, 11);
total = num1 + num2;
}
}
Now, I am using this one on Page_Load event like this :
Captcha c = new Captcha();
protected void Page_Load(object sender, EventArgs e)
{
Label2.Text = c.N1.ToString();
Label3.Text = c.N2.ToString();
}
How can I accomplished this one?
Thanks.

Answer 1

Since you are creating object of Captcha outside the Page Load event, it will get re-created whenever a call to the page happens.
You might be aware that internet is state-less so whenever there is a call to the Page, a new page gets generated, and hence new Captcha object. So you need to maintain the Captcha object in some state management like view state.
Your code should be something like this.
Captcha c;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
c = new Captcha();
Label2.Text = c.N1.ToString();
Label3.Text = c.N2.ToString();
ViewState["c"] = c;
}
}
Then on button click you need to type cast the viewstate back to "c". Something like this.
//button click
c = (Captcha)ViewState["c"];
if(TextBox1.Text.Equals......)
Maybe you need to mark your Captcha class as serializable as it might throw error.
I hope this will help.
Regards,
Samar