Maintain Random Number Across Postbacks

Question

1.00/5 (2 votes)

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I am making a "guess the number" feature for a website, but when I type a number and click "guess", the whole page reloads and generates another random number. How can I fix this problem?

C#

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

public partial class _Default : System.Web.UI.Page
{

    int number;


    protected void Page_Load(object sender, EventArgs e)
    {
        Random genrator = new Random();
        number = genrator.Next(0, 30);
        lbl_start.Text = (" jag tänker på ett tal mellan 1-100 gissa den om du kan!!");

    }



    protected void btn_gissa_Click(object sender, EventArgs e)
    {



        int guess = Convert.ToInt32(txt_matain.Text);

        if (guess > number)
        {
            lbl_gissa.Text = ("mindre" + number);
        }
        if (guess < number)
        {
            lbl_gissa.Text = ("större");
        }

        if (guess == number)
        {
            lbl_gissa.Text = ("du gissa talet grattis!!");
        }


    }


}

Posted 31-May-13 6:36am

walanw

Updated 31-May-13 11:38am

AspDotNetDev

v2

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Comments

CHill60 31-May-13 12:43pm

Are you checking for postback?

walanw 31-May-13 12:49pm

what? i don´t understand

2 solutions

Solution 2

This type of value should be stored in Session. This code will do what you are looking for (modify it appropriately for your specific needs):

ASP.NET

<%@ Page Language="C#" %><!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title>Random Number</title>
</head>
<body>
  <form id="frmMain" runat="server">
    <asp:TextBox runat="server" ID="txtGuess" />
    <asp:Button runat="server" ID="btnGuess" Text="Guess" onclick="btnGuess_Click" />
    <div>
      <asp:Label runat="server" ID="lblGuess" />
    </div>
  </form>
</body>
</html>

<script runat="server">
  protected void Page_Load(object sender, EventArgs e)
  {
    if (!Page.IsPostBack)
    {
      Random rnd = new Random((int)(DateTime.Now.Ticks % int.MaxValue));
      Session["RandomNumber"] = rnd.Next(0, 30);
    }
  }
  protected void btnGuess_Click(object sender, EventArgs e)
  {
    int guess;
    if (int.TryParse(txtGuess.Text, out guess))
    {
      int number = (int)Session["RandomNumber"];
      lblGuess.Text = number.ToString() + "_" + guess.ToString();
    }
  }
</script>

Posted 31-May-13 11:55am

AspDotNetDev

Comments

walanw 1-Jun-13 2:49am

thank you for your time but i think my code work now all i need is using classes in this game
can you give an example on how a class can be if you would create class for this game?

AspDotNetDev 1-Jun-13 14:08pm

Is this a homework assignment? If so, I suggest you ask your teacher for help in the areas you do not understand.

walanw 1-Jun-13 14:11pm

my teacher is not that good and she dont answer the most of my questions thats why am here on this site if got the anwers from my teacher i would not come here ijust want an example on how to make and use classes with code:)

AspDotNetDev 1-Jun-13 14:15pm

http://msdn.microsoft.com/en-us/library/vstudio/x9afc042.aspx

walanw 1-Jun-13 14:24pm

i have read all of this for a week ago but i still have some problms understanding, like how can u add an class to code, like what do i write to add the class to my code ?

AspDotNetDev 1-Jun-13 14:27pm

Please ask a new question, and be very clear about what you understand and what you do not understand and what you have tried that did not work. The Code Project Quick Answers area is not intended for tangential discussions. It is intended for very specific questions with very specific answers.

walanw 1-Jun-13 14:31pm

i will do it thanks alot :D

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ZurdoDev · Accepted Answer · 2013-05-31T07:10:00

Solution 1

Just add

C#

if (!IsPostBack){}

to the Page Load. Buttons postback causing Page_Load to run first and then the button click event runs. Just wrap your code into an if (!IsPostBack)

C#

    protected void Page_Load(object sender, EventArgs e)
    {
if (!IsPostBack)
{
        Random genrator = new Random();
        number = genrator.Next(0, 30);
        lbl_start.Text = (" jag tänker på ett tal mellan 1-100 gissa den om du kan!!");
 }
    }

Posted 31-May-13 7:10am

ZurdoDev

Comments

walanw 31-May-13 13:17pm

but if i do this the guess number will always be 0 i dont know why :S what can i do to this ?

ZurdoDev 31-May-13 13:30pm

So, you need to generate the random number in the button click event instead.

walanw 31-May-13 13:41pm

it does not work, how would you write this code to make it work? do i have to find another way to write it ?

ZurdoDev 31-May-13 14:10pm

I don't know. I don't know what you want to do exactly. If you just want to compare the number they typed in vs. a random number just put it all in to the button click event. Otherwise, please be clear on what you need.

walanw 31-May-13 14:15pm

i just want to make a working guess number game for website using asp.net c# but this way does not seem working well, do you have another way to do it so it works ? if you don¨t have time to do that its ok thank you so far :)

ZurdoDev 31-May-13 14:18pm

Why doesn't it work. Can you be clear please?

walanw 31-May-13 14:21pm

the code genrate a new number when ever i press enter or gissa button "guess" i tried the code "ispostback" the number dont chnage this time but instead it always 0 and i tried again and did like you said and genrated the random number inthe click button but the same happend i get always 0 as random number

ZurdoDev 31-May-13 14:24pm

Are you saying that genrator.Next(0, 30); is always giving you 0?

walanw 31-May-13 14:25pm

yes

ZurdoDev 31-May-13 14:41pm

Refer to this link, http://stackoverflow.com/questions/5264412/why-does-random-next-always-return-the-same-number

walanw 31-May-13 14:43pm

this should work i will try it thank you so much for you time !! :)

walanw 31-May-13 15:09pm

i tried if (!IsPostBackEventControlRegistered)
{
Random genrator = new Random();
number = genrator.Next(0, 101);
lbl_start.Text = (" jag tänker på ett tal mellan 1-5 gissa den om du kan!!");
} and this time it worked :D thank you so much !!

ZurdoDev 31-May-13 15:11pm

Good to hear. I think intellisense might have gotten you. You want
if (!IsPostBack)
and not
if (!IsPostBackEventControlRegistered)
but if it works, maybe you just leave it. :)

walanw 31-May-13 15:14pm

oh i was wrong you were right from the begining it is if (!IsPostBack) i just added static int number; that static changed everything :)thank for helping i thank you alot from the bottom om my heart you dont know how happy i am to make this code work i know its not a big deal but yeah :)

ZurdoDev 31-May-13 15:15pm

Good to hear.

walanw 31-May-13 15:43pm

just a last thing am sorry for being annoying, can you please make me an exempel of class that i can use to this game ?

ZurdoDev 31-May-13 15:57pm

Sorry, I don't understand.

walanw 31-May-13 15:58pm

i wanna make a class for this game how do i do i mean i want a class to relate to my program

ZurdoDev 31-May-13 16:00pm

It's already in a class. "public partial class _Default"

However, you could just create a new class with a GenerateRandomNumber function or something like that. It seems pretty trivial so I am not sure exactly what you are looking for.

walanw 31-May-13 16:04pm

classes are for properties right? so i want to make my labels in another color like if you are near the guess the guess will be written in green and something like that like if (guess > number)

{
lbl_gissa.Text = ("mindre" + number);
} the text will be green here

if (guess < number)
{
lbl_gissa.Text = ("större");
} and here will be red you know what i mean?

ZurdoDev 31-May-13 16:05pm

Not really. Classes are for combining like functions of code. You could just change the label color in that code.

walanw 31-May-13 16:06pm

yeah that what i meant like i wanna make functions on the class that i will will create u just want an example of how am going to do i t if you have time :)

AspDotNetDev 31-May-13 17:41pm

Don't use a static variable. If you do that, all visitors of the site will have the same random number. The random number will also change for all users whenever another user visits the page. Surely you do not want that.