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ASP.NET Essential Training
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Using session variables


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ASP.NET Essential Training

with David Gassner

Video: Using session variables

When you need to persist data in memory between page requests that's unique to each individual user and those pages aren't connected to each other through the web form system, that is, they aren't posting to each other, you can choose to use session variables. A session variable is stored in memory on the server but a copy of the session variable is stored for each individual user session and that session in turn is managed with cookies. A cookie is a bit of data that's created on the server and sent back to the browser along with the response to what an http request.
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  1. 18m 44s
    1. Welcome
      1m 42s
    2. Prerequisites
      2m 21s
    3. Using the exercise files
      1m 32s
    4. Upgrading exercise file websites for ASP.NET 4.5 (NEW)
      2m 40s
    5. What's new in ASP.NET 4 (NEW)
      3m 48s
    6. What's new in ASP.NET 4.5 (NEW)
      3m 23s
    7. What's new in this course update (NEW)
      3m 18s
  2. 33m 34s
    1. Understanding how ASP.NET works
      5m 52s
    2. Installing Microsoft Visual Web Developer 2008
      3m 43s
    3. Installing Visual Studio Express 2012 for web (NEW)
      2m 12s
    4. Hello World: Creating your first ASP.NET web site
      4m 28s
    5. Creating pages with dynamic output
      7m 39s
    6. Understanding the development web server
      4m 49s
    7. Exploring the development environment
      4m 51s
  3. 40m 2s
    1. Understanding Microsoft SQL Server
      5m 47s
    2. Installing SQL Server Express
      6m 51s
    3. Exploring SQL Server Management Studio Basic
      4m 23s
    4. Creating a new database
      8m 51s
    5. Connecting to the database in ASP.NET
      5m 35s
    6. Testing SQL queries
      3m 53s
    7. Presenting a dataset in an ASP.NET page
      4m 42s
  4. 25m 31s
    1. Understanding ASP.NET web form pages
      5m 51s
    2. Separating presentation and logic with code files
      4m 17s
    3. Adding web form controls to a page
      5m 25s
    4. Handling postback data in a web form page
      5m 50s
    5. Using data binding expressions
      4m 8s
  5. 48m 37s
    1. Creating a testing environment
      4m 40s
    2. Declaring and using a simple variable
      6m 14s
    3. Declaring and using a complex object
      6m 16s
    4. Using loops
      6m 52s
    5. Using functions
      9m 25s
    6. Using trace statements
      4m 47s
    7. Debugging with breakpoints
      5m 45s
    8. Commenting code
      4m 38s
  6. 17m 43s
    1. Creating web controls
      5m 53s
    2. Registering a user control on a web form page
      3m 25s
    3. Registering controls globally in the web.config file
      3m 53s
    4. Adding public properties to a web control
      4m 32s
  7. 19m 7s
    1. Understanding Cascading Style Sheets (CSS)
      5m 36s
    2. Attaching external CSS files
      3m 12s
    3. Defining a CSS selector
      6m 10s
    4. Using CSS class selectors in server controls
      4m 9s
  8. 30m 34s
    1. Presenting data with the GridView control
      5m 49s
    2. Controlling GridView paging and appearance
      5m 46s
    3. Editing data with the GridView control
      6m 57s
    4. Presenting data with the DataList control
      5m 42s
    5. Formatting data with binding expressions
      6m 20s
  9. 36m 46s
    1. Using the DetailsView control
      7m 33s
    2. Inserting data with the DetailsView control
      6m 36s
    3. Redirecting page requests
      9m 39s
    4. Creating an update page
      6m 20s
    5. Linking to update pages from the list page
      4m 3s
    6. Deleting database records
      2m 35s
  10. 22m 15s
    1. Customizing forms with item editing templates
      6m 7s
    2. Adding validator controls to a form
      6m 40s
    3. Controlling the validation error message display
      6m 24s
    4. Using the ValidationSummary control
      3m 4s
  11. 29m 49s
    1. Creating a query with joined tables
      8m 6s
    2. Replacing control style properties with CSS
      5m 50s
    3. Creating a CSS file for printing
      3m 14s
    4. Suppressing elements in printed web pages
      5m 47s
    5. Selecting data for a report
      6m 52s
  12. 11m 14s
    1. Understanding ViewState and managing postbacks
      4m 36s
    2. Using session variables
      6m 38s
  13. 20m 57s
    1. Turning on forms authentication
      1m 51s
    2. Creating a page to log in users
      4m 18s
    3. Creating a page to set up new users
      4m 6s
    4. Understanding the security database
      3m 27s
    5. Configuring security in the web.config file
      2m 59s
    6. Creating a page to log out users
      4m 16s
  14. 27m 56s
    1. Installing IIS on Windows XP
      6m 32s
    2. Installing ASP.NET 3.5 on Windows XP
      1m 39s
    3. Deploying a site on Windows XP
      5m 9s
    4. Installing Information Internet Services (IIS) on Windows Vista, Windows 7, and Windows 8
      1m 56s
    5. Configuring ASP.NET 3.5 on Windows Vista
      2m 15s
    6. Deploying an application on Windows Vista
      3m 29s
    7. Scripting a database for deployment
      3m 36s
    8. Exporting database scripts in SQL Server Management Studio 2012 (NEW)
      3m 20s
  15. 2m 0s
    1. Where to go from here
      2m 0s

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ASP.NET Essential Training
6h 24m Beginner Apr 28, 2009 Updated Feb 13, 2013

Viewers: in countries Watching now:

Thousands of businesses have used Microsoft ASP.NET to build professional, dynamic websites. In this course, web developer David Gassner demonstrates the tools needed to build and deploy a dynamic site using ASP.NET 3.5 or 4.5. Covering everything from installing and configuring Visual Web Developer 2008 or Visual Studio Express 2012 for Web and SQL Server Express to creating web form pages, this course is designed to give beginning and intermediate developers hands-on experience.

Topics include:
  • Storing data with SQL Server
  • Using the GridView control to present and edit dynamic data
  • Creating a data entry system
  • Attaching external CSS files
  • Creating pages to log in and authenticate visitors
  • Installing Internet Information Services (IIS) on Windows XP and Windows Vista
  • Deploying an ASP.NET website on IIS
Subjects:
Developer Web Servers Programming Languages Web Development
Software:
ASP.NET
Author:
David Gassner

Using session variables

When you need to persist data in memory between page requests that's unique to each individual user and those pages aren't connected to each other through the web form system, that is, they aren't posting to each other, you can choose to use session variables. A session variable is stored in memory on the server but a copy of the session variable is stored for each individual user session and that session in turn is managed with cookies. A cookie is a bit of data that's created on the server and sent back to the browser along with the response to what an http request.

In the ASP.NET Framework and with many other application servers, session cookies are created automatically. Whenever a page is loaded, the server will detect that a new user session is starting and it creates a session cookie known as the User Session Token and sends that back to the browser with its first response. The browser then includes that cookie with each subsequent request, essentially reminding the server of which the user session is making the request. You can add arbitrary session variables. Each session variable can be of many types: strings, numbers or even complex arrays containing complete data sets.

In this video, I'm going to demonstrate how to create a session variable in response to a button click and then how to read that session variable in a totally separate page. I'll start at the file SessionVarCreate.aspx. In this page, there is currently a TextBox control with an ID of TextBox1 and a button control with the text label of Set Variable. I will double-click on the button and that takes me to the buttons, Button1_ Click method. This is the event handler function responding to the Click event on the server. Within the server environment, I'm going to create a variable in the session scope. There is an object named Session. It's a dynamic object, which means that you can add arbitrary property names. Within the function I'll say Session and then I'll put in a bracket and within the brackets, I'll add the ID or the key for the property I want to add. You can use any string value as the key for the property.

I will use a property of mySessionVar, then I'll close the expression with the closing bracket, then I'll put in the equal assignment operator and then I'll assign the value of the SessionVar to TextBox1.txt. The data typing of this value is a string because the text property of the TextBox returns a string. But again, you can put in many kinds of complex data into the Session object. Now, after I have stored the data in memory, I'll then redirect to the read page using Response.Redirect and I'll pass in the name of the page I want to go to. SessionVarRead.aspx. Because I'm using the Redirect command, I'm not posting to the other page and therefore, I would not be able to use the Viewstate object to pass the data, but when I set the value in the Session object, I'm storing the data in server memory and when the other page loads, it will send that cookie and it will have access to this data.

I will save that page and then go to the page SessionVarRead.aspx. In this file there is a button with a label of Read Variable and a label control with an ID of Output label. I'll double-click the Read Variable button and that takes me to the Click event handler for that button and here I'll retrieve the value of that session variable. Within the button Click event handler, I'll set the Output Label's Text property and then once again, I'll use the value Session["mySessionVar"].

There is one more bit of code you must include though. The text property of the Label object expects a string but there is no way for the ASP.NET Framework at this point to know that the value I stored in the session with the key of mySessionVar is a string. In C#, you explicitly datatype the returned value. Using this sort of code, place the cursor before the Session object and then to clear the datatype of the object, use the datatype within a pair of parenthesis. If you are working in Visual Basic, you would instead use the syntax as string after Session mySessionVar.

Now I'll save the changes and I'll run the page initially without coming from the first page. When the page loads in the browser, I'll click the button and you will see that the Label text property is left blank. That's because that variable is not in session or server memory yet, so I'll close the browser and I'll return to the Create Page and run that page in the browser pressing Ctrl+F5. I will type in a value into the TextBox and click the button Set Variable. That takes me to the Read page, then I'll click the Read Variable button and you will see that the value is retrieved and displayed.

Now, one of the questions that comes up about sessions is do they persist between browser sessions. That is to say if the user closes all of the browser windows and then opens the website again, is that session data still accessible to them? And the answer is No. I will go back to the Read page and load it into the browser again. Notice that I have closed all of my browser windows before this part of the test and I'll click the button and show that the data does not show up. Here is what's going on. Remember I said that cookies are used to link the web browser session to the data on the server. The types of cookies that are being used here are called memory or session cookies and the browser doesn't remember those cookies between its on-sessions. These kinds of cookies are not stored persistently on disk by the browser; they are just stored in memory.

So when the user closes all of the browser windows, its session cookies are lost and therefore, the data on the server is lost as well. So data that you placed into the session scope or into the Session object is remembered between page requests, but only for the duration of the current browser session. When the user closes all of their browser windows, that results in destroying the session cookies that are in browser memory and the next time the browser goes to the website, a new session is started automatically. Session variables again can store many different types of data: strings, numbers, arrays and many other complex objects. The most common use of sessions is to store things like shopping cards, user information after authenticating the user and so on and it's a valuable way to glue together the pages of a dynamic website built in ASP.NET.

Find answers to the most frequently asked questions about ASP.NET Essential Training.


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Q: When trying to create a new database, after pasting the text into the SQL Management Suite and executing the query, the database is not created and the following message appears: 

Database 'mybookstore' does not exist. Make sure that the name is entered correctly

What is causing this error?
A: The database must be explicitly created before the script is run. Start by right-clicking on the Databases item in the left panel, then follow the prompts to create the database. Then retry the query.
Q: I am running into problems installing the latest version of ASP.NET. Has the installation procedure changed since this tutorial was recorded?
A: The installation process for the newest version of ASP.NET and its associated tools is a little different than in ASP.NET 3.5, which was used to record this course. You can download Microsoft Web Platform Installer 2.0 from:
<a href="http://www.microsoft.com/web/downloads/platform.aspx" target="blank">http://www.microsoft.com/web/downloads/platform.aspx</a>
Microsoft Web Platform Installer 2.0 includes everything you need:
ASP.NET 4?
Visual Web Developer 2010?
SQL Server Express
You must have one of the following operating systems:
Windows 7?
Windows Vista?
Windows Vista SP1?
Windows XP SP2+?
Windows Server 2003 SP1+?
Windows Server 2008?
Windows Server 2008 R2
You must have administrator privileges on your computer to run the Web Platform Installer.
Q: This course was updated on 2/13/2013. What changed?
A: Since this course was recorded, Microsoft has released both ASP.NET 4.5, the latest version of the server-side web application server, and Visual Studio Express 2012 for Web (the successor product to Visual Web Developer). Both have been adapted to work on Windows 8. There will be some visual changes and some functional changes, but most of the server-side code shown in the course is the same. This update provides a map for those working with the latest software so they can navigate their way through the course.

In particular, we added <em>What's new</em> movies for both ASP.NET 4 and 4.5, a movie explaining the significance of the update, a movie on installing SQL Server Express 2012, and one on exporting database scripts in SQL Server Management Studio 2012, as well as updates to visuals throughout the course.
Q: In the chapter on user authentication, an authentication error results when I try to use the Login component or register a new user. How do I fix this?
A: This is a known error that can occur when using the original release of Visual Studio 2012 Express for Web. Update your copy of Visual Studio for Web to at least maintenance release 1, and then try the exercise again.
 
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