Coding for client-side storage in C#.NET

Creator Code39 in C#.NET Coding for client-side storage

To get a cookie, you have to first leave a cookie In part of the response to a client say, after they log in you want to tell the platform to save information in the Cookies collection Remember that cookies are plain text anyone can read them Never store something that can be used by someone wearing a proverbial black hat I almost always create a SystemGuid (a globally unique identifier) and use that to track information that I then persist somewhere in my back-end data store What is even better is to store information about the session itself and have an understanding that the information will be removed from the database after some time limit This prevents the impersonation of the user by someone who intercepts the cookie There are a lot of options, but check out the best practices offered by Microsoft and other organizations before setting up your cookie strategy If I want to store information about the session in the cookie, and tell the database that my customer is using that session, I generate a Guid and save it in both places Then I can retrieve the cookie at the next request, compare it to the available Guids in the user collection, and find the user in question Here is an example of setting the cookie based on session information:

using using using using using using System; SystemCollectionsGeneric; SystemLinq; SystemWeb; SystemWebUI; SystemWebUIWebControls;

namespace _4 { public partial class Cookies : SystemWebUIPage { WebUser currentUser = new WebUser(); List<WebUser> usersInDatabase = new List<WebUser>(); protected void Page_Load(object sender, EventArgs e) {

if (!PageIsPostBack) { //This is a first request, so we need to set the cookie Guid sessionGuid = new Guid(); currentUserSessionId = sessionGuid; //Tell the database about the new user usersInDatabaseAdd(currentUser); //Set the cookie ResponseCookiesAdd(new HttpCookie( SessionId , sessionGuid ToString())); } } } //This class would be in the library somewhere, //not actually in this file public class WebUser { public Guid SessionId { get; set; } } }

So now the user has the cookie, and the next request comes in I need to grab the cookie from the collection and search my known user base to get the information that I need The boldface in the code below indicates the code added:

using using using using using using System; SystemCollectionsGeneric; SystemLinq; SystemWeb; SystemWebUI; SystemWebUIWebControls;

namespace _4 { public partial class Cookies : SystemWebUIPage { WebUser currentUser = new WebUser(); List<WebUser> usersInDatabase = new List<WebUser>(); protected void Page_Load(object sender, EventArgs e) { if (!PageIsPostBack) { //This is a first request, so we need to set the cookie Guid sessionGuid = new Guid(); currentUserSessionId = sessionGuid; //Tell the database about the new user usersInDatabaseAdd(currentUser); //Set the cookie ResponseCookiesAdd(new HttpCookie( SessionId , sessionGuid ToString())); } else {

//The is a postback so we need to get the cookie string cookieSession = RequestCookiesGet( SessionId )Value ToString(); Guid sessionGuid = new Guid(cookieSession); var returningUser = from u in usersInDatabase where uSessionIdToString() == sessionGuidToString() select u; foreach (var user in returningUser) { //Better only be one currentUser = user; } } } //This class would be in the library somewhere, //not actually in this file public class WebUser { public Guid SessionId { get; set; } } }

A lot of the stuff we use to store in a cookie is managed by the ASPNET engine Session state, the most common example (discussed earlier), is now handled by the ViewState object You can store information in the ViewState like you would in a variable, and the information is encoded for you and kept in a special field in the markup ViewState has its problems, and a lot of people don t like to use it In fact, many ASPNET applications in enterprises have turned it off to save bandwidth and prevent poor coding practices In these cases, a return to cookies is your best bet to maintain a constant communication with the user