ASP.NET
ASP.NET

Session expired but doesnt redirect, throws an error

I have the code below to redirect when the session is expired. Instead of redirecting after the session is expired, it throws this error

Object reference not set to an instance of an object.

Why is that? why isn't it redirecting? how can I fix it?

private int BusinessNameId
    {
        get
        {
            if (string.IsNullOrEmpty(Session["BusinessId"].ToString()))
            {
                Response.Redirect("~/SessionExpired.aspx");
            }
            return int.Parse(Session["BusinessId"].ToString());
        }
    }

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LVL 7

CamilliaAsked: 2013-01-06

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LVL 28

Chinmay PatelConnect With a Mentor Enterprise ArchitectCommented: 2013-01-06

Hi Farzadw,

No. Problem is this statement:
Session["BusinessId"].ToString();

What happens if your session is expired, Session["BusinessId"] will return a null.

Now your code is always executed from most inner to most outer brackets, so it will first try to execute your .ToString() method on a null object and that will throw an exception even before your string.IsNullOrEmpty get's a chance to execute itself.
Also another trick you can use for such scenarios is to use as operator

string businessId = Session["BusinessId"] as string;

Regards,
Chinmay.

LVL 20

Obadiah ChristopherConnect With a Mentor Commented: 2013-01-06

You need to check for null

if(Session["BusinessId"] == null)
{
    Response.Redirect("~/SessionExpired.aspx");
return null;
}
else
return int.Parse(Session["BusinessId"].ToString());

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LVL 7

CamilliaAuthor Commented: 2013-01-06

doesnt IsNullOrEmpty check for null?

LVL 20

Obadiah ChristopherCommented: 2013-01-06

Session["BusinessId"].ToString() should throw an object reference error.

LVL 7

CamilliaAuthor Commented: 2013-01-06

But i have it in a IsNullOrEmpty..

Now, If I change it to below..in that case it goes to redirect line. No object null error. Why is it like that...is it because string businessId = Session["BusinessId"].ToString();
initializes it to an empty string?

private int BusinessNameId
{
get
{
string businessId = Session["BusinessId"].ToString();
if (string.IsNullOrEmpty(businessId))
{
Response.Redirect("~/SessionExpired.aspx");
}
return int.Parse(Session["BusinessId"].ToString());
}
}

LVL 7

CamilliaAuthor Commented: 2013-01-06

So I should change it what informaniac has?

LVL 28

Chinmay PatelEnterprise ArchitectCommented: 2013-01-06

Even this should work:

private int BusinessNameId
    {
        get
        {
             string businessId = Session["BusinessId"] as string;
            if (string.IsNullOrEmpty(businessId))
            {
                Response.Redirect("~/SessionExpired.aspx");
            }
            return int.Parse(Session["BusinessId"].ToString());
        }
    }