lightswitch Grid 控件添加 CheckBox 多选

最新推荐文章于 2016-10-25 08:45:53 发布

转载最新推荐文章于 2016-10-25 08:45:53 发布 · 82 阅读

本文介绍了一种在LightSwitch Grid中通过一行代码实现多选功能的方法，并详细解释了背后的实现原理，包括如何使用扩展方法为网格添加复选框列，以及如何处理选择状态的变化。

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.

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:

          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 >= 
          1
          ; ;
         
          }

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)