Adding Objects To Session

ASPnoob

I have a list called List < Accounts > where I can add customers' info after supplying the needed data and clicking the Add button on my webform. To persist my data between postbacks I stored my data in a session variable then retrieve them from that session variable later on. The problem is the session variable only shows one account even though I added multiple accounts. The folloewng is my code.

List accts = new List();

protected void btnShowAccountDetails_Click(object sender, EventArgs e)
{
StringBuilder acctDetails = new StringBuilder();

if (Session\["acctObjects"\] != null)
accts = (List)Session\["acctObjects"\];

foreach(Account acct in accts)
{
 acctDetails.Append("ID: "+ acct.Name + " Account ID: " + acct.AccountID + "<br/>");
}   

litCtrShowAccountDetails.Text = acctDetails.ToString();

}

protected void btnAddAcctount_Click(object sender, EventArgs e)
{
Account acct = new Account();
StringBuilder acctDetails = new StringBuilder();

if (!String.IsNullOrEmpty(txtName.Text))
{
acct.Name = txtName.Text;	
}
else
{
//Display Error message
ScriptManager.RegisterStartupScript(this, GetType(), "EmptyName", "EmptyNameAlert();", true);
}

if (!String.IsNullOrEmpty(txtAccountID.Text))
{
acct.AccountID = txtAccountID.Text;	
}
else
{
//Display Error message
ScriptManager.RegisterStartupScript(this, GetType(), "EmptytAccountID", "EmptytAccountIDAlert();", true);
}

accts.Add(acct);
Session\["acctObjects"\] = accts;

}

Please help me resolve this issue, thanks in advance.

ZurdoDev

You instantiate accts as a new List of Accounts. Then all you do is add 1 account when the button is clicked. So, when you click the button again, the variable is accts is being set as new again.

There are only 10 types of people in the world, those who understand binary and those who don't.

Mathi Mani

The issue is where you add the accts which is a List<Account> to the session. These two lines of code always replace whatever object present in Session["acctObjects"]

accts.Add(acct);
Session["acctObjects"] = accts;

To avoid the overwrite, whenever you want to add a Account to List<Account> stored in session, get the List from session, add new Account to that list and store it back to session. Here is how you can do it.

if (Session["acctObjects"] != null)
accts = (List<acct>)Session["acctObjects"];
accts.Add(acct);
Session["acctObjects"] = accts;

ASPnoob

Thanks for replying your suggestion is very helpful.

F ES Sitecore

Slightly pedantic but to avoid your code throwing an error when the session times out I'd code this more defensively

if (Session["acctObjects"] != null)
accts = (List<acct>)Session["acctObjects"];
else
accts = new List<acct>();

accts.Add(acct);
Session["acctObjects"] = accts;

Richard Deeming

Alternatively:

const string AcctObjectsSessionKey = "acctObjects";
...
accts = (List<acct>)Session[AcctObjectsSessionKey] ?? new List<acct>();
accts.Add(acct);
Session[AcctObjectsSessionKey] = accts;

That avoids the possibility of the session object being removed between the existence check and the retrieval. :)

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

F ES Sitecore

Fair point, not sure if that is possible though.

Richard Deeming

I've seen too many bugs caused by "impossible" events to take the risk. :-D

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

F ES Sitecore

I agree, which is why I'd use "as" rather than casting as you did in your example as your code would error if the session variable existed but contained a different object ;P Sessions last for the period of the page execution. It has to exist for the page to start executing so can't time-out mid execution. It'll only become unavailable if something terminal has happened like the app unloading, and your code will stop working in that instance anyway.