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UWP 从 TemplateSelector 更改为用户控件不再显示绑定

[英]UWP Changing from TemplateSelector to user Control does not show binding anymore

 原文  2020-05-05 17:24:50  4   1    c#/ xaml/ data-binding/ uwp/ user-controls

问题描述

遵循 Richard Zhang - MSFT 在我的问题UWP Treeview 中提供的工作解决方案，当我调整 window 的大小时，数据选择器在 App.g.cs 中生成错误我尝试将更清晰的第二组数据模板转换为代码并尝试解决其他一些可视化问题。 代码可以编译，但没有显示任何内容。

使用 TreeView 模板选择器的工作代码：

    <Page.Resources>
        <DataTemplate
            x:Key="ItemTemplate"
            x:DataType="model:MTreeViewBase"
            x:DefaultBindMode="OneWay">
            <winui:TreeViewItem IsExpanded="False" ItemsSource="{x:Bind Visits}">
                <controls1:TreeViewControl Data="{x:Bind}" />
            </winui:TreeViewItem>
        </DataTemplate>

        <DataTemplate
            x:Key="PAZContentTemplate"
            x:DataType="model:MTreeViewPaz"
            x:DefaultBindMode="OneWay">
            <StackPanel>
                <TextBlock Style="{StaticResource TitleTextBlockStyle}" Text="{x:Bind Name}" />
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Cognome" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Cognome}" />
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="1"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Nome" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="1"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Nome}" />
                </Grid>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Telefono 1" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Telef1}" />
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="1"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Telefono 2" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="1"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Telef2}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="0"
                        Margin="{StaticResource XSmallTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Fax" />
                    <TextBlock
                        Grid.Row="3"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Fax}" />
                </Grid>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>

                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Grid.ColumnSpan="5"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Indirizzo" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Grid.ColumnSpan="5"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Indir}" />

                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Cap}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="1"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Citta}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="2"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text=" (" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="3"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Cap}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="4"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text=")" />
                    <TextBlock
                        Grid.Row="3"
                        Grid.Column="0"
                        Grid.ColumnSpan="5"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Nazione}" />

                </Grid>
                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Codice Fiscale" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.CodFis}" />

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Nato il " />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind BornDate}" />
                <TextBlock
                    Margin="{StaticResource XSmallTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="in" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Naton}" />
                <StackPanel Orientation="Horizontal">
                    <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Natoa}" />
                    <TextBlock Text=" (" />
                    <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Natop}" />
                    <TextBlock Text=")" />
                </StackPanel>

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Clinica" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Clinica}" />

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Presentato da" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.PresDa}" />

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Assicurazione" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Assicurazione}" />
            </StackPanel>
        </DataTemplate>
        <DataTemplate
            x:Key="APPContentTemplate"
            x:DataType="model:MTreeViewVisit"
            x:DefaultBindMode="OneWay">
            <StackPanel>
                <TextBlock
                    Foreground="{x:Bind ImageColor}"
                    Style="{StaticResource TitleTextBlockStyle}"
                    Text="Analisi Patologia Prossima" />
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Clinica" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Visit.(model:TApp.Clinica)}" />
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="1"
                        Margin="{StaticResource MediumLeftTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Data" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="1"
                        Margin="{StaticResource MediumLeftMargin}"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Visit.(model:TApp.DataS)}" />
                </Grid>

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Descrizione" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Visit.(model:TApp.Descr)}" />
            </StackPanel>
        </DataTemplate>
    </Page.Resources>

        <templateSelectors:TreeViewDataContentTemplateSelector
            x:Key="TreeViewDataContentTemplateSelector"
            APPTemplate="{StaticResource APPContentTemplate}"
            PAZTemplate="{StaticResource PAZContentTemplate}" />

        <ScrollViewer Grid.Column="1" Padding="{StaticResource DetailPageMargin}" x:DefaultBindMode="OneWay">
            <ContentControl Content="{x:Bind SelectedItem}" ContentTemplateSelector="{StaticResource TreeViewDataContentTemplateSelector}" />
        </ScrollViewer>

当我单击 TreeView 中的项目时，面板显示正确的信息。

但如果我试试这个：

TrewView.xaml

       <ScrollViewer Grid.Column="1" Padding="{StaticResource DetailPageMargin}" >
            <controls1:TreeViewContentControl Data="{x:Bind (model:MTreeViewBase)SelectedItem, Mode=OneWay}"    />
        </ScrollViewer>

TreeViewContentControl.xaml

<UserControl
    x:Class="TitoDoc2020.Views.TreeViewContentControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:TitoDoc2020.Views"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:model="using:TitoDoc2020.Models"
    mc:Ignorable="d"
    d:DesignHeight="300"
    d:DesignWidth="400">

    <UserControl.Resources>
        <DataTemplate
            x:Name="PAZContentTemplate"
            x:DataType="model:MTreeViewPaz"
            x:DefaultBindMode="OneWay">
            <StackPanel>
                <TextBlock Style="{StaticResource TitleTextBlockStyle}" Text="{x:Bind Name}" />
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Cognome" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Cognome}" />
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="1"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Nome" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="1"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Nome}" />
                </Grid>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Telefono 1" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Telef1}" />
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="1"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Telefono 2" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="1"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Telef2}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="0"
                        Margin="{StaticResource XSmallTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Fax" />
                    <TextBlock
                        Grid.Row="3"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Fax}" />
                </Grid>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>

                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Grid.ColumnSpan="5"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Indirizzo" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Grid.ColumnSpan="5"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Indir}" />

                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Cap}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="1"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Citta}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="2"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text=" (" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="3"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Cap}" />
                    <TextBlock
                        Grid.Row="2"
                        Grid.Column="4"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text=")" />
                    <TextBlock
                        Grid.Row="3"
                        Grid.Column="0"
                        Grid.ColumnSpan="5"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Paz.Nazione}" />

                </Grid>
                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Codice Fiscale" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.CodFis}" />

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Nato il " />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind BornDate}" />
                <TextBlock
                    Margin="{StaticResource XSmallTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="in" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Naton}" />
                <StackPanel Orientation="Horizontal">
                    <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Natoa}" />
                    <TextBlock Text=" (" />
                    <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Natop}" />
                    <TextBlock Text=")" />
                </StackPanel>

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Clinica" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Clinica}" />

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Presentato da" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.PresDa}" />

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Assicurazione" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Paz.Assicurazione}" />
            </StackPanel>
        </DataTemplate>

        <DataTemplate
            x:Name="APPContentTemplate"
            x:DataType="model:MTreeViewVisit"
            x:DefaultBindMode="OneWay">
            <StackPanel>
                <TextBlock
                    Foreground="{x:Bind ImageColor}"
                    Style="{StaticResource TitleTextBlockStyle}"
                    Text="Analisi Patologia Prossima" />
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="0"
                        Margin="{StaticResource MediumTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Clinica" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="0"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Visit.(model:TApp.Clinica)}" />
                    <TextBlock
                        Grid.Row="0"
                        Grid.Column="1"
                        Margin="{StaticResource MediumLeftTopMargin}"
                        Style="{StaticResource DetailSubTitleStyle}"
                        Text="Data" />
                    <TextBlock
                        Grid.Row="1"
                        Grid.Column="1"
                        Margin="{StaticResource MediumLeftMargin}"
                        Style="{StaticResource DetailBodyBaseMediumStyle}"
                        Text="{x:Bind Visit.(model:TApp.DataS)}" />
                </Grid>

                <TextBlock
                    Margin="{StaticResource MediumTopMargin}"
                    Style="{StaticResource DetailSubTitleStyle}"
                    Text="Descrizione" />
                <TextBlock Style="{StaticResource DetailBodyBaseMediumStyle}" Text="{x:Bind Visit.(model:TApp.Descr)}" />
            </StackPanel>
        </DataTemplate>
    </UserControl.Resources>

    <Grid>
        <ContentControl x:Name="MainContent" />
    </Grid>
</UserControl>

TreeViewContentControl.xaml.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using TitoDoc2020.Models;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236

namespace TitoDoc2020.Views
{
    public sealed partial class TreeViewContentControl : UserControl
    {
#if LOG
        private static readonly NLog.Logger Logger = NLog.LogManager.GetCurrentClassLogger();
#endif
        public MTreeViewBase Data
        {
            get { return (MTreeViewBase)GetValue(DataProperty); }
            set { SetValue(DataProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Data.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty DataProperty =
            DependencyProperty.Register("Data", typeof(MTreeViewBase), typeof(TreeViewContentControl), new PropertyMetadata(null, new PropertyChangedCallback(Data_Changed)));

        private static void Data_Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (e.NewValue != null)
            {
                var instance = d as TreeViewContentControl;
                if (e.NewValue is MTreeViewPaz)
                {
                    instance.MainContent.ContentTemplate = instance.PAZContentTemplate;
                }
                else
                {
                    //instance.MainContent.ContentTemplate = instance.VisitTemplate;
                    switch (((MTreeViewVisit)e.NewValue).Type)
                    {
                        // Generic Visits
                        case "APP":
                            instance.MainContent.ContentTemplate = instance.APPContentTemplate;
                            break;
                        default:
                            if (e.NewValue != null)
                            {
#if LOG
                                Logger.Error("Should never be default");
#endif
                            }
                            break;
                    }
                }

            }
        }
        public TreeViewContentControl()
        {
            this.InitializeComponent();
        }
    }
}

它不显示 x:Bind 中的任何内容。 页面更改正确，显示 static 文本但不是真实数据。

我认为我所做的与其他控件完全相同，但无法理解我搞砸了什么

1 个解决方案

解决方案1
 0  2020-05-06 18:52:21

感谢Peter Spada和他的惊人帮助，我能够让它工作：

这就是问题所在：我将 instance.MainContent.ContentTemplate 设置为带有x:DataType=”model:MTreeViewPaz”的 DataTemplate。 但是， instance.MainContent从未设置其Content或DataContext ，因此它使用默认的DataContext 。 默认DataContext继承自 XAML 树并来自根ShellPage ：

这就是InvalidCastException无法将ShellPage转换为MTreeViewPaz的原因。

我可以通过手动设置 DataContext 来修复它，如下所示。

TreeViewContentControl.xaml.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using TitoDoc2020.Models;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236

namespace TitoDoc2020.Views
{
    public sealed partial class TreeViewContentControl : UserControl
    {
#if LOG
        private static readonly NLog.Logger Logger = NLog.LogManager.GetCurrentClassLogger();
#endif
        public MTreeViewBase Data
        {
            get { return (MTreeViewBase)GetValue(DataProperty); }
            set { SetValue(DataProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Data.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty DataProperty =
            DependencyProperty.Register("Data", typeof(MTreeViewBase), typeof(TreeViewContentControl), new PropertyMetadata(null, new PropertyChangedCallback(Data_Changed)));

        private static void Data_Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (e.NewValue != null)
            {
                var instance = d as TreeViewContentControl;
                if (e.NewValue is MTreeViewPaz)
                {
                    instance.MainContent.ContentTemplate = instance.PAZContentTemplate;
                }
                else
                {
                    //instance.MainContent.ContentTemplate = instance.VisitTemplate;
                    switch (((MTreeViewVisit)e.NewValue).Type)
                    {
                        // Generic Visits
                        case "APP":
                            instance.MainContent.ContentTemplate = instance.APPContentTemplate;
                            break;
                        default:
                            if (e.NewValue != null)
                            {
#if LOG
                                Logger.Error("Should never be default");
#endif
                            }
                            break;
                    }
                }

                instance.MainContent.DataContext = e.NewValue;

            }
        }
        public TreeViewContentControl()
        {
            this.InitializeComponent();
        }
    }
}

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