Error in Session

[Gunawan]

Hi All,
I am using VS 2005 to build this page.
One the code file I use this code
using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;



public partial class one : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

if (Session["FirstLoadTime"] == null)

{

Session["FirstLoadTime"] = DateTime.Now.ToString("T");

}

Label1.Text = "Page first loaded at " +
Session["FirstLoadTime"].ToString();



if (IsPostBack)

{

Label1.Text += "<br> Welcome back, "

+ Session["UserName"].ToString();

}

}

protected void Button1_Click(object sender, EventArgs e)

{

if (Session["UserName"] == null)

{

Session["UserName"] = TextBox1.Text;

}



}

}



But why I always get this error though I have type something in the textbox1





Server Error in '/WebData' Application.
--------------------------------------------------------------------------------

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the
current web request. Please review the stack trace for more information
about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set
to an instance of an object.

Source Error:

Line 22: if (IsPostBack)
Line 23: {
Line 24: Label1.Text += "<br> Welcome back, "
Line 25: + Session["UserName"].ToString();
Line 26: }

 

[Gunawan]

If I Using this code
using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;



public partial class one : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

string sUserName;

if (Session["FirstLoadTime"] == null)

{

Session["FirstLoadTime"] = DateTime.Now.ToString("T");

}

Label1.Text = "Page first loaded at " +
Session["FirstLoadTime"].ToString();



if (IsPostBack && Session["UserName"] != null)

{

sUserName = (string)Session["UserName"];

Label1.Text += "<br> Welcome back, "

+ sUserName + "!"

+"<br> IsPostBack: " + IsPostBack.ToString();

}

else

{

Label1.Text += "<br> Welcome back, unknown user."

+"<br> IsPostBack: " + IsPostBack.ToString();

}

}

protected void Button1_Click(object sender, EventArgs e)

{

Session["UserName"] = TextBox1.Text;



}

}



I need click button1 twice to make username appear on label1.

Why? any idea?



TIA

Gun

 

[Gunawan]

I see.... Now I can figure out what happened.

I would to know what is the best practice if I want to do something like
this

If user click button1 on one.aspx I would like to perform some action before
directing user to another page (two.aspx).
Action that I want to perform effecting Session["DataMS"]
Session["DataMS"] use in page two.aspx.

does button1 onclick perform before pageload on two.aspx?

TIA
Gun

PageLoad event fires before OnClick one. That's why Session["UserName"] is
null in PageLoad.

Eliyahu

Hi All,
I am using VS 2005 to build this page.
One the code file I use this code
using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;



public partial class one : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

if (Session["FirstLoadTime"] == null)

{

Session["FirstLoadTime"] = DateTime.Now.ToString("T");

}

Label1.Text = "Page first loaded at " +
Session["FirstLoadTime"].ToString();



if (IsPostBack)

{

Label1.Text += "<br> Welcome back, "

+ Session["UserName"].ToString();

}

}

protected void Button1_Click(object sender, EventArgs e)

{

if (Session["UserName"] == null)

{

Session["UserName"] = TextBox1.Text;

}



}

}



But why I always get this error though I have type something in the
textbox1





Server Error in '/WebData' Application.
--------------------------------------------------------------------------------

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the
current web request. Please review the stack trace for more information
about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not
set to an instance of an object.

Source Error:

Line 22: if (IsPostBack)
Line 23: {
Line 24: Label1.Text += "<br> Welcome back, "
Line 25: + Session["UserName"].ToString();
Line 26: }

 

[Eliyahu Goldin]

PageLoad event fires before OnClick one. That's why Session["UserName"] is
null in PageLoad.

Eliyahu

 

[Eliyahu Goldin]

Can you put the redirecting statement in the button1 onclick?

Eliyahu

I see.... Now I can figure out what happened.

I would to know what is the best practice if I want to do something like
this

If user click button1 on one.aspx I would like to perform some action
before directing user to another page (two.aspx).
Action that I want to perform effecting Session["DataMS"]
Session["DataMS"] use in page two.aspx.

does button1 onclick perform before pageload on two.aspx?

TIA
Gun

PageLoad event fires before OnClick one. That's why Session["UserName"]
is null in PageLoad.

Eliyahu

Hi All,
I am using VS 2005 to build this page.
One the code file I use this code
using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;



public partial class one : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

if (Session["FirstLoadTime"] == null)

{

Session["FirstLoadTime"] = DateTime.Now.ToString("T");

}

Label1.Text = "Page first loaded at " +
Session["FirstLoadTime"].ToString();



if (IsPostBack)

{

Label1.Text += "<br> Welcome back, "

+ Session["UserName"].ToString();

}

}

protected void Button1_Click(object sender, EventArgs e)

{

if (Session["UserName"] == null)

{

Session["UserName"] = TextBox1.Text;

}



}

}



But why I always get this error though I have type something in the
textbox1





Server Error in '/WebData' Application.
--------------------------------------------------------------------------------

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the
current web request. Please review the stack trace for more information
about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not
set to an instance of an object.

Source Error:

Line 22: if (IsPostBack)
Line 23: {
Line 24: Label1.Text += "<br> Welcome back, "
Line 25: + Session["UserName"].ToString();
Line 26: }