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Using trace statements

From: ASP.NET Essential Training

Video: Using trace statements

When working with programming, it's useful to be able to see what's going on inside the application at runtime. Visual Web Developer provides a powerful debugger and the .NET Framework itself provides additional tools, both of which allow you to see what's happening by either adding code to your page or creating what are known as break points. In this video, I'm going to describe the use of tracing. The ability to output information to the webpage at runtime. This is a feature of the .NET Framework rather than Visual Web Developer the tool. And so it's done completely with code.

Using trace statements

When working with programming, it's useful to be able to see what's going on inside the application at runtime. Visual Web Developer provides a powerful debugger and the .NET Framework itself provides additional tools, both of which allow you to see what's happening by either adding code to your page or creating what are known as break points. In this video, I'm going to describe the use of tracing. The ability to output information to the webpage at runtime. This is a feature of the .NET Framework rather than Visual Web Developer the tool. And so it's done completely with code.

I will start off with the file LoopingCSharp.aspx. In this file, there is already some code that's doing some looping with a For loop and a While loop. If you didn't do the previous exercise where this file was created, you can create a new file now using a For loop or a While loop. I'll save this file under a name. Selecting File > Save LoopingCSharp.aspx as and I'll name the new file Tracing.aspx.

The concept of tracing will be the same regardless of whether you are working C# or Visual Basic. So we'll only demonstrate it with the single file. In order to use the tracing capability you must turn it on first. You can do this either one page at a time or you can do it globally for your entire website in the web.config file. I am going to demonstrate turning on tracing for just one file. I'll go up to the top of the file, to the page declaration and I'll add an attribute Trace = true. By default the Tracing capability is turned off. Now I'll save and I'll run the page, selecting Debug > Start Without Debugging.

As the page starts up it displays the code and then at the bottom of the page, a whole bunch of information is dumped on to the screen. You can find out what's going on as the page is loaded, by looking not just at the messages but also at the time stamps, the numeric values. If for example, a page is a long time to load, you can trace and find out where the time lag is happening by comparing the numeric values. As you scroll down, you will see a lot of information including the timing, the tracing and you will see also see something called the control tree which shows you what kind of objects that are part of the page.

Down toward the bottom, you will see a listing of different variable types. I have described how to use variable types in other videos in the series. There is the Headers Collection which lets you see what kind of information is being sent from the browser to the server and lots more information. So that's how you turn tracing on. Now let's take a look at how you can use this feature and create your own custom messages. I'll close the browser and return to the page. I'll press Alt+ Shift+Enter to go to full screen and then I'm going to take out the While loop in this portion of the page. I only need the For loop to demonstrate this and within the For loop, I'll place the cursor after the call to the output function and I'll use this code, Trace.Write.

Trace is the name of a class that's always available to you. As you can see in the pop-up help, the Trace.Write function, we see it's a number of arguments. The only one that's really required in this context is the string. The first argument and I'm going to pass in a value which is the same as I'm passing to the output message, The value of counter is, and I'll append the value of the counter variable. So now I'll be writing to the trace section at the bottom of the page.

I'll save my changes and I'll run the page. When the page first loads I see the trace information for the initial load. Then I'll click the Run Code page and I'll see the value of the counter is 1 and 2 in the top section that output is being handled by my custom output function. But then if I scroll down, I'll see in the Trace section the same information. Notice that I see time stamps indicating how long it took to get from one phase of creating the file to the next phase. So once again, if you are having performance problems in a page, the Trace functionality is a great way of tracking down where the delay might be happening.

As I mentioned, you can also turn Tracing on for the entire website. You do this in the web.config file. I won't go through those steps here but if you do need to turn tracing on for the entire site for some reason, you can do it through a centralized mechanism.

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This video is part of

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ASP.NET Essential Training

79 video lessons · 49184 viewers

David Gassner
Author

 
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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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