question about Session

Valerie Meunier

3y1.1kASP.NET

Hi,

this code works perfect (without the last line!). The elements of list are retained by the Session variable after each postback. But i'm wondering how it can work without the last line: Session["time"] = time; . When a new element is added to the list, if Session["time"] is not present, then it's not updated and doesn't contain the new element. According to me, the line time = (List)Session["time"]; can't contain anyyhing.

Any explanation for this: why is that line Session["time"] = time; not necessary?

Thanks

using System;
using System.Collections.Generic;

public partial class WebForm : System.Web.UI.Page
{
List time = new List();

protected void Page_Load(object sender, EventArgs e)
{
TextBox1.Focus();
if (!Page.IsPostBack)
{
Session["time"] = time; // empty
}
}
protected void TextBox1_TextChanged(object sender, EventArgs e)
{
Label1.Text = "";
time = (List)Session["time"];
time.Add(Convert.ToInt32(TextBox1.Text));
time.Sort();
for (int i=0;i< time.Count;i++)
Label1.Text += time[i].ToString() + " ";
TextBox1.Text = "";
//Session["time"] = time; // works without this line
}
}

9 Replies

Know the answer? Post it — somebody with the same question will find it here.

Valerie Meunier3y ago
I wonder why nobody has tried.

I did this as test:

if (!Page.IsPostBack)
{
Label2.Text += "not postback";
Session["time"] = time; // empty
}
else
{
Label2.Text += "postback";
}
And this gives not postback postback postback postback ...

This proves that it's executed only one time. Try yourself.
0
Munib Butt3y ago
Somehow, the below is executed each time.

if (!Page.IsPostBack)
{
Session["time"] = time; // empty
}

Otherwise, the session cannot be set.
0
Valerie Meunier3y ago
May I suggest that you copy/paste this code and try yourself in VS. In aspx-file, you only need a label and a textbox.

This is the first line:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm.aspx.cs" Inherits="time.WebForm" %>

Thanks
+1
Valerie Meunier3y ago
I tested it with a label inside the IF(): the first time, the label got a value, after that no. I'm sure it(s running properly:

if (!Page.IsPostBack)
{
Session["time"] = time; // empty
}

How can i test it with the debugger?
+1
Sachin Singh3y ago
if

if (!Page.IsPostBack)
{
Session["time"] = time; // empty

}

if the above line is not executing then there is no way session could be set.

Have you tested it with debugger?
+1
Valerie Meunier3y ago
if i do that, i see only the last added value.
+1
Sachin Singh3y ago
Are you sure if you remove time = (List)Session["time"]; then it stops working?
+1
Valerie Meunier3y ago
Thanks for replying, but there must be a reason for that. No idea?
+1
Sachin Singh3y ago
put a debugger at below line
```
if (!Page.IsPostBack)
            {
                Session["time"] = time; // empty
}
```
if with each text change the flow is not entering inside the above curley braces (and setting session) (obviously it shouldn't enter for postbacks) then yes, it is strange .

Your session should be empty.
+1