Session Update Issue in C#

Question

0.00/5 (No votes)

See more:

Hi,

I am getting List of Object from Session, then Update that list of object in that case session value is automatically updated.

This is the piece of code :-

XML

if(Session["StudentData"]!=null)
        {
            List<Student> testStudent = Session["StudentData"] as List<Student>;
            Response.Write("<br>Value in Session <br/>");
            DisplayData(testStudent);

            int i = 0;
            foreach (Student obj in testStudent)
            {
                if (i == 2)
                {
                    obj.Name = "Adi";
                    obj.Age = 23;
                    break;
                }
                i = i + 1;
            }

            Response.Write("<br>Modify Value in Session <br/>");
            DisplayData(testStudent);

            Response.Write("<br>Value in Session <br/>");
            DisplayData(Session["StudentData"] as List<Student>);




        }

How to avoid this ?
Why this happens ? Please explain in detail.
Waiting for your Reply.

Thanks.

Posted 3-May-12 1:34am

Aditya Magotra

Updated 25-Mar-16 8:58am

Add a Solution

3 solutions

Solution 3

For future reference:

In instances like this, a copy constructor is typically preferred when working with objects stored in session without updating the object in session.

@MSDN How to: Write a Copy Constructor

Cloning isn't preferred in the majority of situations due to lack of specified cloning depth (deep vs shallow).

In your case, a collection class with a copy constructor or

C#

.ToList<t>();</t>

could be used to obtain a copy.

C#

var studentsInSession = Session["Student"] as List<Student>
var students = studentsInSession.ToList(); 

students.Add(new Student("John", "Smith"));

This would allow the modification of the list without reflecting the change to the session.

Posted 25-Mar-16 8:58am

Code.Combustion

Solution 1

instead of updating the same list why not take a copy of it yourself.

XML

if(Session["StudentData"]!=null)
        {
            List<Student> testStudent = Session["StudentData"] as List<Student>;
            Response.Write("<br>Value in Session <br/>");
            DisplayData(testStudent);

            int i = 0;
            List<Student> another;
            foreach (Student obj in testStudent)
            {
                another[i] = obj;
                if (i == 2)
                {
                    another[i].Name = "Adi";
                    another[i].Age = 23;
                    break;
                }
                i = i + 1;
            }

            Response.Write("<br>Modify Value in Session <br/>");
            DisplayData(another);

            Response.Write("<br>Value in Session <br/>");
            DisplayData(Session["StudentData"] as List<Student>);




        }

Posted 3-May-12 1:47am

Rahul Rajat Singh

Comments

[no name] 3-May-12 8:19am

hi,
Thanks for reply reply.

I tried this but still same issue....session is getting updated.

Thanks.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

pietvredeveld · Accepted Answer · 2012-05-03T10:42:00

The session is updated because the variable testStudent is equal to the list in Session["StudentData"]. That is the first statement in you're code : List<student> testStudent = Session["StudentData"] as List<student>;

Remember these are all reference types. So testStudent == Session["StudentData"]. Equally all objects in Session["StudentData"] are in testStudent.

When it is you're goal to change the objects in testStudent list without changing the session, you must clone the objects before add them to a new list, the testStudent list;

To achieve that derive you're Student class from ICloneble and add the following extension class to you're project.

C#

static class Extensions
{
        public static IList<t> Clone<t>(this IList<t> listToClone) where T: ICloneable
        {
                return listToClone.Select(item => (T)item.Clone()).ToList();
        }
}
</t></t></t>

the first statement in you code can the be:

C#

IList<student> testStudent = Session.Clone<student>();
</student></student>