Lightswitch中树形控件的使用

Lightswitch中没有树形展示的方式,也未找到第三方的扩展，只好用silverlight toolkit中的tree来实现。主要实现部门功能（自引用关系)

表定义如下

ID,deptname,ParentID

在LightSwitch中数据实体如下：

后来加了一个IsRoot 主要是用来获取根节点，Ls在查询条件时没办法设置参数值为null,只好将就一下来解决了。

建一个silverligth类库工程解决树的问题，主要二个文件，代码后续。

1.在需要树展示的屏幕中添加一个本地变量，类型Dept类型，同时编辑其过涉条件为IsRoot=true

2.在需要树展示的屏幕合适位置中添加一个自定义控件（就是我们建的工程，将数据源Screen赋上)，命名为DeptTree（后面会用到)

3，在屏幕保存的地方，加上保存处理

  partial void EditableDeptmentSetGrid_Saved()
        {
            // 在此编写您的代码。
            DeptTree.refresh();

        }

<UserControl x:Class="SilverLightclassLibrary1.SilverlightTreeControl"
   xmlns="http://scheR_30_11845@as.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://scheR_30_11845@as.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://scheR_30_11845@as.microsoft.com/expression/blend/2008"
    xmlns:mc="http://scheR_30_11845@as.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:SilverLightclassLibrary1"  
    xmlns:sdk="http://scheR_30_11845@as.microsoft.com/winfx/2006/xaml/presentation/sdk"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <UserControl.resources>
        <local:EntityCollectionValueConverter x:Key="EntityCollectionValueConverter" />
    </UserControl.resources>

    <Grid x:Name="LayoutRoot" BACkground="White">
        <StackPanel Orientation="Horizontal">
            <sdk:TreeView Name="treeViewControl" Itemssource="{Binding Screen.DeptTreE}">
                <sdk:TreeView.ItemContainerStyle>
                    <Style TargetType="sdk:TreeViewItem">
                        <Setter Property="IsExpanded" Value="True"/>
                    </Style>
                </sdk:TreeView.ItemContainerStyle>
                <sdk:TreeView.ItemTemplate>
                    <sdk:HierarchicalDataTemplate 
                            Itemssource="{Binding 
                        Converter={Staticresource EntityCollectionValueConverter},ConverterParameter=SubDepts}">
                        <StackPanel Orientation="Horizontal">
                            <TextBlock Text="{Binding Path=deptname,Mode=TwoWay}" 
                                       Margin="5,0" Width="74" />
                        </StackPanel>
                    </sdk:HierarchicalDataTemplate>
                </sdk:TreeView.ItemTemplate>
            </sdk:TreeView>
        </StackPanel>
    </Grid>
</UserControl>

 // By: Karol Zadora-Przylecki (Microsoft)
    // From: http://bit.ly/oNTsJo
    // Ensures that an entity collection is loaded before accessed by UI thread.
    // The binding should use the whole entity object as data binding context
    public class EntityCollectionValueConverter : IValueConverter
    {
        public object Convert(object value,Type targetType,object parameter,System.Globalization.CultureInfo culturE)
        {
            String strErrormessage
                = "Converter parameter should be set to the property name that will serve as source of data";
                
            IEntityObject entity = value as IEntityObject;
            if (entity == null) 
                throw new Argumentexception("The converter should be using an entity object");

            String sourcePropertyName = parameter as String;
            if (String.IsNullOrWhiteSpace(sourcePropertyName)) 
                throw new Argumentexception(strErrormessagE);
            
            // Enumerate the source property using logic dispatcher 
            // and prepare the collection of entities that the control will bind to
            var entities = new ObservableCollection<IEntityObject>();
            var temporaryEntites = new List<IEntityObject>();

            entity.Details.Dispatcher.beginInvoke(delegate
            {
                IEntityCollection eCollection = 
                    entity.Details.Properties[sourcePropertyName].Value as IEntityCollection;
                if (eCollection == null)
                {
                    Debug.Assert(false,"The property " + sourcePropertyName + " is not an entity collection");
                    return;
                }

                // Now we are on the logic thread. We cAnnot just stuff the observable collection
                // with entities because the collection will immediately raise Changed events
                // and this will result in invalid cross-thread access. So we'll use a temporary collection
                // and copy the entites again on the UI thread

                foreach (IEntityObject e in eCollection)
                {
                    temporaryEntites.Add(E);
                }

                Microsoft.LightSwitch.Threading.Dispatchers.Main.beginInvoke(delegate
                {
                    // I wish ObservableCollection had an AddRange() method...
                    foreach (IEntityObject e in temporaryEntites)
                    {
                        entities.Add(E);
                    }
                });
            });

            return entities;
        }

        public object ConvertBACk(object value,System.Globalization.CultureInfo culturE)
        {
            throw new NotImplementedException();
        }
    }