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Editing data with the GridView control

From: ASP.NET Essential Training

Video: Editing data with the GridView control

The GridView control combined with the SqlDataSource control can be used to create a very elegant editing interface where the user sees data listed in an HTML table and then can click a hyperlink to open just the selected row for editing. From there, you can then allow the user to make changes to the data, which will automatically be saved to the server-side database. Most of the code that you need for this is already generated when you drag a GridView control into a page within Visual Web Developer. In this demonstration, I'll show you how to modify the code to turn editing on and then how to block editing of particular columns. I'll work with the file AuthorsWithEditing.aspx and then look at the file in Design View. You'll see that it has a version of the Authors GridView, this time displaying just three columns, the Last Name, First Name and Phone Number.

Editing data with the GridView control

The GridView control combined with the SqlDataSource control can be used to create a very elegant editing interface where the user sees data listed in an HTML table and then can click a hyperlink to open just the selected row for editing. From there, you can then allow the user to make changes to the data, which will automatically be saved to the server-side database. Most of the code that you need for this is already generated when you drag a GridView control into a page within Visual Web Developer. In this demonstration, I'll show you how to modify the code to turn editing on and then how to block editing of particular columns. I'll work with the file AuthorsWithEditing.aspx and then look at the file in Design View. You'll see that it has a version of the Authors GridView, this time displaying just three columns, the Last Name, First Name and Phone Number.

First, I'll turn Editing on, on the GridView control. I'll click on the GridView control and then open the list of available tasks and I'll select Enable Editing. When I select that option that changes a single property of the GridView control. Then I'll save my changes by pressing Ctrl+S and I'll run the page in the browser. When the GridView is displayed now, it shows a new column with a hyperlink next to each row. I'll go down to a particular page, let's say page number 2 and I'll click the Edit link for the first row currently displayed. You'll see that that results in opening up the row for editing, displaying text input controls for each of the columns.

I'll make certain changes to the columns. For example, I'll change Ann's name and add an "e" at the end and then I'll click the Update link. That results in saving the data all the way back to the server-side database. I can prove that the data was actually changed by continuing to navigate around in the pages and you'll see that the updated change has taken or is currently displayed. Now in certain conditions, you may want to allow editing for one column but not others. When you turn editing on for the entire GridView, by default, all columns are editable. You can then go into individual bound fields and turn on a property called ReadOnly.

When you set the ReadOnly property to True for a particular bound field and then you click the Edit link for a row, the columns marked as ReadOnly will be displayed as text rather than displayed with an input control. And then there are some changes you'll need to make in the underlying definition of the SqlDataSource object to make it compatible with your changes to the GridView. Close the browser and return to Visual Web Developer and with the GridView still selected I'll open the list of available tasks and click Edit Columns. Now, let's say that I want the user to be able to edit the phone number, but not the last name or first name. So I'll click the Last Name field in the list of Selected Fields and then I'll go to the Behavior category and locate the ReadOnly property and change it to True.

I'll do the same thing for the First Name. I'll click on the field in the list of Selected Fields. Locate the ReadOnly property and set it to True and then I'll click OK. I'll press Ctrl+S to save my changes and then select Debug > Start Without Debugging to run the page. Now this time when I click the Edit link, you'll see that only the phone number is displayed as an input control. If I cancel, my changes aren't saved. But here is that problem that you'll run into and I'll show you the solution in a moment. I'll click the Edit link. I'll make a small change to the phone number and then click the Update link and I'll see a big old ASP.NET error displayed on the screen.

The problem that you're encountering is shown down here. The message is Cannot insert the value Null into column au_ lname. The problem that you're running into is that the GridView control passes in what's called a Null value or the absence of a value into the Last Name column. You can solve this problem by modifying the structure of the Update SQL statement that's being executed when the page is updated. I'll close the browser and return to Visual Web Developer and then I'll look at the page in Source view and I'll look at it in full screen, so I can see as much code as possible. I'll press Alt+ Shift+Enter. Now, I'll scroll down to the SqlDataSource definition. The problem is here in the UpdateCommand attribute.

The Update statement is expecting to set the values of all of the columns in the backend database table. But I'm only passing in a value for the phone number. So I'm going to reduce the SQL statement. I'll get rid of the column value pair for au_lname. I'll do the same thing for au_fname and its trailing comma. I'll leave the phone number in, but then I'll place the cursor right before the comma after the phone number. I'll hold down the Shift key and then start cursoring over to select as much of the SQL statement as I need to delete and I'll finish selecting text right before the keyword WHERE. Then I'll press the Delete key.

Here is the remaining SQL statement. Update authors. Set phone equal to the phone parameter where the au_id column equals the au_id parameter. So, that's how the Update statement will match the structure of the GridView. I'm only going to be passing in that one value. So I don't need to set up the SQL statement to update more than that column. Then I'll go to the UpdateParameters section of the SqlDataSource definition and I'll do the same thing, this time for the parameters which are being filled in automatically from the GridView. I'll remove the au_lname and au_fname parameters and also remove address, city, state and zip. I'll leave the phone and the Author ID, which are both needed.

Now, I'll save my changes and I'll run the page in the browser once again, selecting Debug > Start Without Debugging. I'll click the Edit link. Once again, I'm only able to edit the phone number because I set the other columns as ReadOnly. I'll make a change to the Phone number. I'll change it to have a trailing number of 1111. I'll click the Update link and you'll see that the data is successfully saved to the database on the server and displayed in the updated page. I can now page forward and back through the data display and you'll see that the data has been saved successfully and is being displayed on the refreshed page.

So, to review the steps for setting up an updatable GridView, in Design View, you turn editing on by selecting the task list and selecting Enable Editing. Then you edit the columns. Set ReadOnly to True for each column you don't want the user to edit. Then go into the Source View and modify the SqlDataSource definition, modify the SQL statement for updating the table so it's only affecting the columns that the user is allowed to edit and then remove the parameters for those columns that are ReadOnly as well. Then you'll be allowing the user to modify the data directly through the GridView with minimal programming on your part.

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This video is part of

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ASP.NET Essential Training

79 video lessons · 49162 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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