ACTIVATING MULTI SELECTION WITH CHECKBOXES IN A LIGHTSWITCH GRID WITH A ONE-LINER

2013/04/02 · by paul van bladel · in Uncategorized

Introduction

In a business app grid, you often need the ability the select multiple rows and apply an action on the selected rows.

lightswitch Grid 控件添加 CheckBox 多选ACTIVATING MULTI SELECTION WITH CHECKBOXES IN A LIGHTSWITCH GRID WITH A ONE-LINER

Wouldn’t it be great if we could inject this via following “one-liner”;

ObservableCollection<Product> SelectedProducts =

new

ObservableCollection<Product>();

partial

void

EditableProductsGrid1_InitializeDataWorkspace(List<IDataService> saveChangesTo)

this

.FindControl(

"grid"

).AddCheckBoxColumnForMultiSelection<Product>(SelectedProducts);

The line that really matters is the extension method “AddCheckBoxColumnForMultiSelection”. It takes at input an ObservableCollection which will hold the selected items.

As you can see, there is a button called “Do Something With Selection”. We can tweak also the CanExecute behavior as follows:

1 2 3 4 5 6 7 8 9 10 11 12

partial

void

DoSomethingWithSelection_Execute()

foreach (

var

item

in

SelectedProducts)

this

.ShowMessageBox(item.ProductName);

partial

void

DoSomethingWithSelection_CanExecute(ref bool result)

result =

this

.Products.SelectedItem !=

null

&& SelectedProducts.Count >=

; ;

This will make sure the button is not clickable if there are no checkboxes checked.

What’s our base infrastructure for doing this?

That’s a bit more involved. But it doesn’t matter, since it’s implemented as an extension method, the whole functionality becomes a … one liner.

using

Microsoft.LightSwitch;

using

Microsoft.LightSwitch.Client;

using

Microsoft.LightSwitch.Presentation;

using

System;

using

System.Linq;

using

System.Collections.ObjectModel;

using

System.Net;

using

System.Windows;

using

System.Windows.Controls;

using

System.Windows.Documents;

using

System.Windows.Ink;

using

System.Windows.Input;

using

System.Windows.Markup;

using

System.Windows.Media;

using

System.Windows.Media.Animation;

using

System.Windows.Shapes;

using

Microsoft.LightSwitch.Framework.Client;

using

Microsoft.LightSwitch.Presentation.Extensions;

using

System.Diagnostics;

using

Microsoft.LightSwitch.Presentation.Implementation;

using

System.Collections.Generic;

namespace

LightSwitchApplication

public

static

class

MultiSelectGridExtensions

public

static

void

AddCheckBoxColumnForMultiSelection<T>(

this

IContentItemProxy gridProxy, ObservableCollection<T> selectedItems) where T :

class

,IEntityObject

EventHandler<ControlAvailableEventArgs> gridProxy_ControlAvailable =

null

gridProxy_ControlAvailable = (s1, e1) =>

DataGrid dataGrid = e1.Control

as

DataGrid;

var contentItem = dataGrid.DataContext

as

IContentItem;

var visualCollection = (contentItem.Value)

as

IVisualCollection;

dataGrid.LoadingRow +=

new

EventHandler<DataGridRowEventArgs>((s2, e2) =>

DataGridColumn column = dataGrid.Columns[0];

var checkBox = column.GetCellContent(e2.Row)

as

CheckBox;

T currentRowItem = e2.Row.DataContext

as

T;

if

(currentRowItem !=

null

checkBox.IsChecked = selectedItems.Contains(currentRowItem);

RoutedEventHandler checkboxClick =

null

checkboxClick = (

(s3, e3) =>

var selectedItem = dataGrid.SelectedItem

as

T;

if

(selectedItem ==

null

return

if

(checkBox.IsChecked ??

false

if

(!selectedItems.Contains(selectedItem))

selectedItems.Add(selectedItem);

else

selectedItems.Remove(selectedItem);

TriggerCanExecute(visualCollection);

});

checkBox.Click += checkboxClick;

});

var col =

new

DataGridTemplateColumn();

var xaml =

@"<DataTemplate  xmlns=""http://schemas.microsoft.com/winfx/2006/xaml/presentation"">

<CheckBox/>

</DataTemplate>"

var dataTemplate = XamlReader.Load(xaml)

as

DataTemplate;

col.CellTemplate = dataTemplate;

dataGrid.Columns.Insert(0, col);

gridProxy.ControlAvailable -= gridProxy_ControlAvailable;

};

gridProxy.ControlAvailable += gridProxy_ControlAvailable;

private

static

void

TriggerCanExecute(IVisualCollection visualCollection)

//this will make sure that the CanExecute method is triggered in a potential button for doing something

//with the selection result.

//not elegant, but no other option...

var currentItem = visualCollection.SelectedItem;

var collection = visualCollection

as

IEnumerable<IEntityObject>;

if

(!visualCollection.SelectedItem.Equals(collection.Last()))

visualCollection.SelectedItem = collection.Last();

else

visualCollection.SelectedItem = collection.First();

visualCollection.SelectedItem = currentItem;

Can I download it?

No, you can’t because I stopped uploading samples, as from today. Full stop.

But, … you can directly inject the functionality with NuGet into the silverlight client project. (at least when you use the latest LightSwitch version)