Monthly Archives: May 2014

May 07 2014
68 Comments
LightSwitch, Visual Studio

LightSwitch 2013 HTML Client – Easily add Multi Item Selection to your Lists and Tables!

Enhancing your LightSwitch List, Tiles and Table controls – Updated!

We have refactored from the earlier build… so please review the new steps!

TableWithPersist
CustomersLimit4

As of May 2014, Out of the Box LightSwitch list, tiles and table controls only allow for selection of a single item.

Until now!

The demo/test drive has been updated showing the new upcoming functionality check it out: MultiSelect Preview

So… we’re like squirrels here, constantly distracted. And so with that said, we’ve nailed down our long term name for the library. Going forward we’ll be branding as LightSwitch Wires, or lsWires for short. Since in reality that’s kind of what we all do. We add the wiring to LightSwitch to make things work or work better. And this naming convention works for our other disciplines like Kendo UI and Syncfusion. We’ll keep the “Wires” branding and just swap out the prefix for the type of wires we’re providing. Thanks for your patience, this is the LAST breaking change.

Now on with it… Within the lsWires library we've provided the functionality to enhance the list and table controls

  • Selection of multiple items
  • Ability to limit the number of selections
  • Select/Unselect all items
  • Get the selected item count
  • Retrieve the data of the selected items
  • Persist selections for the session
  • We no longer take over the ItemTap
  • Multiple lists can be on the same screen
  • Same code base works across all 3 control types

Sounds awesome eh? So lets get started on how to implement this new functionality…

  1. Create a new LightSwitch 2013 HTML Application
  2. Lets name it: itgLsMultiSelect
  3. When at the Start with data screen, click on Attach to external…
  4. Data Source Type: OData Service
  5. OData service endpoint:
    http://services.odata.org/northwind/northwind.svc/
  6. Authentication type: None
  7. Choose the following entities:
    Customer
    Employee
    Product
  8. Name the data source: Northwind
  9. Click the finish button
  10. Close any open editor windows
  11. Save your solution
  12. Over in your your Solution Explorer pain
  13. Add the following NuGet package to the HTML Client project
    lo-dash.js
  14. From our GitHub repository
    Add lsWires.js to your Scripts folder
    Add lsWires.css to your Content folder
  15. Now open up your default.htm file in the client project
  16. Add lo-dash.js followed by lsWires.js to the scripts section
  17. Add the lsWires.css as the last stylesheet
  18. Right click on the Screens folder, select Add Screen…
  19. Select Browse Data Screen
  20. Screen Data: Northwind.Customers
  21. Click ok
  22. Save your solution, run the application
  23. Go ahead and click on items, notice single selection
  24. Stop your application
  25. Click on the Tile List, Customers
  26. Click on Edit PostRender Code in the properties window
  27. To get intellisense, drag from solution explorer the file lsWires.js onto your page
  28. Now we only need ONE line of code to enable multi-select 
    // Enable multi-item selection on this tile control
lsWire.list.enableMultiSelect(contentItem);
  29. Before you can run, remove the default ItemTap that LightSwitch automatically adds for the list. We did not create the view screen that the ItemTap is expecting so you’ll get an error when selecting if you don’t.
  30. Save your solution, run your app
  31. BOOM! Multi-Select enabled!
  32. You can also unselect by clicking a selected item
  33. Hmmmm… how do I get the data of the selected items?
  34. Stop your application
  35. Under the Customer List Tab, add a new Group
  36. Move it right under the Command Bar
  37. Change the type to be a Columns Layout
  38. Then add 3 more Rows Layout under the columns layout
  39. For all 3 change the width setting to Fit to Content
  40. Add a new Button into the first rows layout
  41. Select Write my own method, name it: GetSelected
  42. Double click the button to edit the code
  43. We're going to add a few lines
    Get the list contentItem
    Call our method to get the data, which returns an array of entities
    Then we'll display the data 
    var list = screen.findContentItem("Customers");
var count = lsWire.list.selectedCount(list);
var selected = lsWire.list.selected(list);
var text = "Customers Selected\n\n";
_.forEach(selected, function(item) {
      text += item.CustomerID + " - " + item.CompanyName + "\n";
});
text += "\n\nCount = " + count;
window.alert(text);
  44. Save and run your application
  45. Select a few items, click on Get Selected
  46. Unselect a few, Get Selected, only selected get returned
  47. Ok lets continue going thru adding functionality
  48. Add two local properties, boolean
  49. Name them SelectAll and SetLimits
  50. Drag the SelectAll under the second Rows Layout
  51. Change the control type to be of a Custom Control
  52. Over in the properties window, set the label position to None
  53. Then click on Edit Render Code and add the following 
    	// Render a checkbox
	lsWire.checkbox.render(element, contentItem);

	// When the checkbox changes state, either select all or not
	contentItem.dataBind("screen.SelectAll", function (newValue) {
		if (newValue != undefined) {
			var list = contentItem.screen.findContentItem("Customers");
			lsWire.list.selectAll(list, newValue);
		}
	});
  54. Now drag the SetLimits property under your 3rd Rows Layout
  55. Change the control type to be of a Custom Control
  56. Change its Display Name to: Limit of 4
  57. Change the label position to None
  58. Then click on Edit Render Code and add the following for this one, its a bit more lengthy as we’re adding in some cool features 
    	// Render our checkbox
	lsWire.checkbox.render(element, contentItem);

	// When the checkbox changes state, set or remove our limits
	contentItem.dataBind("screen.SetLimits", function (newValue) {
		
		if (newValue !== undefined) {

			// Our dependent item
			var selectAll = contentItem.screen.findContentItem("SelectAll");

			// Get our list
			var list = contentItem.screen.findContentItem("Customers");

			// Current count of selected items
			var count = lsWire.list.selectedCount(list);

			// If the checkbox is selected, limit to 4 items
			if (newValue != undefined && newValue === true) {

				// Set our limit, returns the limit count
				var ttl = lsWire.list.totalSelectionsAllowed(list, 4);

				// if select all was set, checked
				if (selectAll.value === true)

					// set the property to false, dataBinding will do the rest
					contentItem.screen.SelectAll = false;

				// Else is the current count greater than our limit?
				else if (count > ttl) {

					// Count is greater, so unselect all items
					lsWire.list.selectAll(list, false);
				}

				// Since we are limiting, disable the select all checkbox
				selectAll.isEnabled = false;
			} else {

				// Limit was unselected, renable select all and remove limits
				selectAll.isEnabled = true;
				lsWire.list.totalSelectionsAllowed(list, null);
			}
		}
	});
  59. Its that easy!
  60. Save and run your application
  61. Toggle your limits
  62. Select your 4 items, try and select a 5th
  63. No can do! Now unselect a selected and select another
  64. Notice the Select All is no longer a valid option
  65. Uncheck the Limit of 4
  66. Test again, notice the limitations were removed
  67. So what happens if this was a list vs a Tile List?
  68. Stop your application
  69. In the screen designer, change the control type to List
  70. Run your app, test the functionality
  71. As you see, same code, different control type, same results!
  72. Now you ask… table too?
  73. Yep! Go ahead and change it to a table control
  74. Run and test the app
  75. Same code, works as expected on all 3 controls!

So there you go… an easy, reproduceable method of enabling multi-select on your LightSwitch list controls. You can even have multiple lists on the same screen, each will behave independently. We'll leave that up to you to go play around and test. Our sample project already has a multi-list screen if you want to go check it out.

We’ve added functionality to persist selections for a session. Its also a key part for a table control if you are going to allow your clients to change the sort order by clicking on the columns. You’ll set the control to persistSelections and it won’t be a problem. Check out the sample project for the code, its quite simple. Also check out the live preview on how it works.

Obviously if you are using an ItemTap to get to an edit/view screen, you would not implement this, but you could, since we no longer take that over and we do allow for persistent selections. But for most, selection and batch processing, this is the ticket.

One final note regarding the Select All functionality. We are selecting and working with rendered items. So with virtual scrolling, not all items from a query have been returned and rendered. Which means if you do a Select All, scroll and more data comes down, the new data is not selected. Of course one could go and press the Select All button again, or you could do a dataBind and fire off another Select All. But I don't see many instances of where that is appropriate. But you could.

Enjoy! More to come…