Checking session if empty or not

I want to check that session is null or empty i.e. some thing like this:

if(Session["emp_num"] != null)
{

   if (!string.IsNullOrEmpty(Session["emp_num"].ToString()))
            {
                //The code
            }
}

Or just

 if(Session["emp_num"] != null)
    {

       // The code
    }

because sometimes when i check only with:

       if (!string.IsNullOrEmpty(Session["emp_num"].ToString()))
                {
                    //The code
                }

I face the following exception:

Null Reference exception

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

Use this if the session variable emp_num will store a string:

 if (!string.IsNullOrEmpty(Session["emp_num"] as string))
 {
                //The code
 }

If it doesn’t store a string, but some other type, you should just check for null before accessing the value, as in your second example.

Method 2

if (HttpContext.Current.Session["emp_num"] != null)
{
     // code if session is not null
}

• if at all above fails.

Method 3

You need to check that Session["emp_num"] is not null before trying to convert it to a string otherwise you will get a null reference exception.

I’d go with your first example – but you could make it slightly more “elegant”.

There are a couple of ways, but the ones that springs to mind are:

if (Session["emp_num"] is string)
{
}

or

if (!string.IsNullOrEmpty(Session["emp_num"] as string))
{
}

This will return null if the variable doesn’t exist or isn’t a string.

Method 4

You should first check if Session["emp_num"] exists in the session.

You can ask the session object if its indexer has the emp_num value or use string.IsNullOrEmpty(Session["emp_num"])

Method 5

If It is simple Session you can apply NULL Check directly Session["emp_num"] != null

But if it’s a session of a list Item then You need to apply any one of the following option

Option 1:

if (((List<int>)(Session["emp_num"])) != null && (List<int>)Session["emp_num"])).Count > 0)
 {
 //Your Logic here
 }

Option 2:

List<int> val= Session["emp_num"] as List<int>;  //Get the value from Session.

if (val.FirstOrDefault() != null)
 {
 //Your Logic here
 }

Method 6

Check if the session is empty or not in C# MVC Version Lower than 5.

if (!string.IsNullOrEmpty(Session["emp_num"] as string))
{
    //cast it and use it
    //business logic
}

Check if the session is empty or not in C# MVC Version Above 5.

if(Session["emp_num"] != null)
{
    //cast it and use it
    //business logic
}

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0