Scope of static Variable in multi-user ASP.NET web application

Question

Does static variables retain their values across user sessions?

I have a ASP.NET web application where I have two buttons. One for setting the static variable value, another for Showing the static variable value.

namespace WebApplication1 {     public partial class WebForm1 : System.Web.UI.Page {     public static int customerID;      protected void Page_Load(object sender, EventArgs e)     {      }      protected void ButtonSetCustomerID_Click(object sender, EventArgs e)     {         customerID = Convert.ToInt32(TextBox1.Text);     }      protected void ButtonGetCustomerID_Click(object sender, EventArgs e)     {         Label1.Text = Convert.ToString(customerID);     } }  } 

While this works in single-user environment, What happens if there are 2 users simultaneously logged in from two computers, User 1 sets the value as 100, then User 2 sets the value as 200. after that user 1 invokes the Get Value button. What will he see as the value?

Answer 1

Does static variables retain their values across user sessions?

Yes, that's why you should be VERY careful when you use static variables in a web app. You will run in concurrency issues as more than one thread servicing a request can modify the value of the variable.

While this works in single-user environment, What happens if there are 2 users simultaneously logged in from two computers, User 1 sets the value as 100, then User 2 sets the value as 200. after that user 1 invokes the Get Value button. What will he see as the value?

The user will see 200 afterwards.