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Communicating with the web site

From: Visual Studio 2010 Essential Training

Video: Communicating with the web site

I'd like to show you how to connect to web servers and retrieve information. The site I'm going to use for the project is bing.com. I'll start by looking at how Bing queries are formatted. As you can see, I have the Bing web site open and in the URL, I'm going to change the query string to show you how our queries really run against the Bing servers. I'm going to type the word "search" and then a question mark, and then the letter q= and then my search term, wpf, and press Enter. So let's examine this search query.

Communicating with the web site

I'd like to show you how to connect to web servers and retrieve information. The site I'm going to use for the project is bing.com. I'll start by looking at how Bing queries are formatted. As you can see, I have the Bing web site open and in the URL, I'm going to change the query string to show you how our queries really run against the Bing servers. I'm going to type the word "search" and then a question mark, and then the letter q= and then my search term, wpf, and press Enter. So let's examine this search query.

The search means you want to do a search, the q stands for query, and then the equal sign says to assign the WPF string to the query string. If I change this to another word, say "lynda", then you see I now have a different search query. Now, one of many interesting things that Bing does that a lot of the other search engines don't do is that if you put an ampersand here, and then say format=rss, it will return your search results as an RSS feed, and then you can point your RSS reader at this feed and get a constant update for this topic.

So, I'm going to use this string when I go talk to the Bing server in my code. So now I need to switch over to Visual Studio. And I'm going to come down here and double-click on the MainWindow.xaml.cs. This is the code from the earlier movie. I did make one little change here. Now, one of the things you can do in C# when you're making a call to a function, or a method as I like to say, is that you can use name parameters now in C# 4. So, this is the name of the parameter, showAsRSS, and I can use that and then a colon. I find that it makes my code easier to read.

My job now is to write some code in this SendToBing function. The first thing I'm going to do in this function is verify whether the user entered a search term. You might recall that this text box here is called searchText. So, I'm going to write an if-then statement. I'm doing a Ctrl+Tab now to switch back to the other screen, and then I'm going to say if. Now I'm going to press the Tab key twice because "if" is a code snippet, and it will stub in the basics of an if statement. And then I'm going to say string.IsEmpty, actually I mean string .IsNullOrEmpty, and then a couple of parentheses here and then searchText.Text.

So what this says is look at the text box, see if the user has typed something in. If it's null or empty, then I'm going to show a MessageBox and say, "Please enter," something like that, okay? Now let's verify that this works. I'm going to compile my application, save my changes-- you may not see that dialog on your machine--and then I'm going to debug the application by choosing Start Debugging, which will launch my application. Now, if I click on the Search Bing button, I get my MessageBox.

If I click on the Get RSS button, I see the same MessageBox. If I type a Search Term here--wpf--and click the button, I don't see the dialog, but nothing else interesting happens yet because I haven't written the code to talk to the Bing server. So let's do that next. I return back to Visual Studio. I'm going to close this Output window on the bottom of the screen, and then the next thing I'm going to do is do is write a little bit of code here in the SendToBing function to establish a connection to Microsoft's Bing servers. To do that, I'm going to use a class called the WebClient.

I'll declare a variable and instantiate an instance of this class. Now I can format a URL and send that to the web client, and I'll get a response back from that server. Next, I am going to take this code that I have down here, and I'm going to uncomment it by clicking on this Uncomment button down here, and then I'm going to cut that, Ctrl+X, and paste that in here. So, if you say show as RSS, I'm going to build this string using that Bing search syntax I just showed you a few minutes ago. And I'm going to take the data from the text box and then place it in the string right here.

So you see how that equals q= and then whatever is typed in the TextBox. Then I'll send that off to the Bing servers. Now, I'm getting some red squiggles here because I need a variable to hold this URL. So I'll come up here and type in "string url;", and then these red squiggles should go away. And then down here at the bottom, I'm going to call the WebClient and say, "I would like to download a string." So, what I'm going to do is I'm going to send the information over the server. The server is going to send me back a result, and I'm going to say, "I want that back as a string." And I want to do it on a second thread.

I want to do it on a background worker thread so I don't block the UI, so I'm going to choose this one here, DownloadStringAsync, and one more parenthesis right there. So this says, "Start a second thread. Go talk to the server." Here, I'm doing a little magic. I've got this plain string, but that's not enough for this. It needs it formatted to something called the URI, which is a special type in .NET. That's why I'm saying new Uri, and then I'm passing the string, the url into that Uri class.

I'm about ready to go. I need to know when Bing returns the information to me. So, I'm going to add one more bit of code up here at the top. I'm going to say WebClient .DownloadStringCompleted. This event fires when the results come back from the Bing servers. So, what I'm going to do is I'm going to press the Tab key to finish typing, then the Plus sign, then the Equal sign, and then Visual Studio's going to help me write the next couple lines of code. I'm going to press Tab once, because it says press TAB to insert, and then it says press TAB to generate the wc_ DownloadStringCompleted in this class.

I'll press Tab again, and it just wrote this function for me down here. This code will run when the download is complete, and all I'm going to do down here is set my browser to NavigateToString. And I'll pass it in. The piece of information we're going to get returned from the web server, it will come in this variable right here. So I'll say e.Result. I think I am ready to run this application.

Debug > Start Debugging. I'll type in "wpf", and then I'll click the Get RSS button. I need some formatting. I would need to do some data binding and make sure that this gets loaded in a list box or a treeView. I'll show you how to do that in another demo. Now, let me click on the Search Bing button. I'll type in "lynda" this time. And for some reason on my machine, I'm getting these script errors. I just have to click the No button four times, and now you see my browser running inside my application is showing the entire HTML results coming back from the Bing servers.

Now, we've got a working WPF application. By using the WebClient class, we reached out to the Bing web site and retrieved the search results. It would be nice to store the history of my searches in a database. That's the topic of the next movie, where I show you how to work with data and data binding.

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This video is part of

Image for Visual Studio 2010 Essential Training
Visual Studio 2010 Essential Training

86 video lessons · 31447 viewers

Walt Ritscher
Author

 
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  1. 2m 3s
    1. Welcome
      1m 2s
    2. Using the exercise files
      1m 1s
  2. 7m 19s
    1. Understanding the Visual Studio versions
      3m 51s
    2. Setting up your developer computer
      3m 28s
  3. 58m 2s
    1. Creating a Visual Studio project
      4m 58s
    2. Working with Solution Explorer
      6m 32s
    3. Working with big projects
      3m 53s
    4. Taking a tour of the Integrated Developer Environment (IDE)
      8m 36s
    5. Introducing drag-and-drop UI design
      7m 38s
    6. Working with the Properties window
      6m 44s
    7. Looking at Server Explorer
      7m 4s
    8. Exploring the new Help engine
      6m 41s
    9. Setting options for the IDE
      5m 56s
  4. 39m 25s
    1. Creating a simple WPF application
      1m 32s
    2. Building the UI with the editors
      9m 14s
    3. Working with the application code
      3m 37s
    4. Communicating with the web site
      7m 15s
    5. Connecting your data
      8m 4s
    6. Binding to an RSS feed
      5m 4s
    7. Packaging and deploying the application
      4m 39s
  5. 39m 46s
    1. What languages are supported in Visual Studio 2010?
      1m 17s
    2. Exploring basic settings for the Code Editor
      5m 35s
    3. Writing a C# program
      6m 48s
    4. Writing a VB program
      6m 29s
    5. Working with C++
      6m 38s
    6. Working with F Sharp
      6m 9s
    7. Font and color options
      6m 50s
  6. 1h 5m
    1. Formatting your code
      6m 43s
    2. Navigating your code
      7m 44s
    3. Using the Task List
      2m 26s
    4. Commenting your code
      2m 45s
    5. Documenting your code
      8m 26s
    6. Using IntelliSense effectively
      7m 0s
    7. Working with code snippets
      6m 25s
    8. Refactoring your code
      5m 15s
    9. Understanding code generation
      2m 10s
    10. Generating code with T4
      6m 29s
    11. Using the Class View, Class Designer, and Class Diagram tools
      5m 51s
    12. Refactoring VB with CodeRush Xpress
      4m 33s
  7. 1h 11m
    1. Working with project and item templates
      8m 38s
    2. Creating a console application
      7m 5s
    3. Creating a class library
      6m 26s
    4. Creating a web site with ASP.NET
      7m 37s
    5. Creating a rich internet application with Silverlight
      6m 57s
    6. Creating a classic Windows application with Windows Forms
      10m 31s
    7. Creating a dramatic Windows application with Windows Presentation Foundation (WPF)
      4m 41s
    8. Creating a WCF service
      9m 1s
    9. Using an existing WCF service
      6m 38s
    10. Navigation UI designs with the Document Outline view
      3m 41s
  8. 33m 18s
    1. Creating a data project with SQL Project
      6m 24s
    2. Clarifying the confusion on .NET Data
      3m 31s
    3. Using ADO.NET in your application
      6m 50s
    4. Creating typed datasets
      7m 55s
    5. Using the data binding tools
      8m 38s
  9. 30m 13s
    1. Debugging code
      9m 32s
    2. Working with the Watch and other debug windows
      7m 46s
    3. Other debugging techniques
      6m 50s
    4. IntelliTrace historical debugging in Visual Studio Ultimate
      6m 5s
  10. 17m 56s
    1. Understanding Visual Studio editions and test tools
      2m 22s
    2. Verifying your code with unit tests
      8m 58s
    3. Running performance and load tests
      6m 36s
  11. 34m 5s
    1. Building your application
      4m 19s
    2. Customizing the build process with MSBuild
      6m 36s
    3. Setting assembly information
      2m 12s
    4. Deploying a basic Windows application
      2m 19s
    5. Creating an installer with Visual Studio
      7m 39s
    6. Creating a ClickOnce application
      5m 13s
    7. Setting up IIS for deploy
      2m 9s
    8. Deploying a Silverlight or ASP.NET application
      3m 38s
  12. 14m 0s
    1. Understanding source control
      2m 9s
    2. Setting up Team Foundation Server source control
      3m 5s
    3. Using Team Foundation Server source control
      8m 46s
  13. 17m 31s
    1. Understanding the .NET Office integration
      4m 16s
    2. Making a Word 2010 application
      7m 54s
    3. Making an Excel 2010 add-in
      5m 21s
  14. 31m 34s
    1. Understanding the extensibility model in Visual Studio
      2m 17s
    2. Adding external tools to the Tools menu
      4m 42s
    3. Creating macros
      7m 16s
    4. Using the Extension Manager
      5m 1s
    5. Creating an MEF add-in
      7m 9s
    6. Deploying and installing an add-in with VSIX
      5m 9s
  15. 25m 34s
    1. Working with configuration files
      5m 37s
    2. Using the Settings Editor
      7m 30s
    3. Using the Resources Editor
      6m 59s
    4. Localizing your resources
      5m 28s
  16. 1m 17s
    1. Goodbye
      1m 17s

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