Question

我一直试图解决这个问题一天，但仍然没有成功。我正在寻找建议下一步的建议。

问题是，每当我从comobobox中选择一个项目时，ViewModel（VM）中的值都已更改，但是当我触发RelayCommand（在同一个VM中）时，所选项目消失（属性为null）。

当我有用户控件（UC）嵌入另一个用户控件时，事情变得复杂，其中提到了组合框控件。

我的父用户控件的xaml是：

<UserControl 
xmlns:lookupPageControl="clr-namespace:LookupPageControl;assembly=LookupPageControl"  x:Class="SelectedLookupsControl.SelectedLookups"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
  mc:Ignorable="d" 
  d:DesignMinWidth="300"
DataContext="{Binding SelectedLookupsPageViewModel, RelativeSource={RelativeSource Self}}">
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="150"/>
        <ColumnDefinition Width="*"/> 
    </Grid.ColumnDefinitions>
    <ScrollViewer Margin="0,0,5,0" Grid.Column="0" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Disabled">
        <ListBox Padding="2" SelectionMode="Single" SelectedIndex="0" ItemsSource="{Binding SelectedLookups}" SelectedItem="{Binding SelectedLookupPage}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Path=LookupViewModel.LookupName}" ToolTip="{Binding Path=LookupViewModel.Description}" ></TextBlock>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </ScrollViewer>
    <GridSplitter Grid.Column="0" Background="Gray" Width="5" HorizontalAlignment="Right" VerticalAlignment="Stretch"  ResizeBehavior="CurrentAndNext"/>
    <DockPanel Grid.Column="1">
        <Border DockPanel.Dock="Top">
            <TextBlock Margin="5,0,5,0" Text="{Binding Path=SelectedLookupPage.LookupViewModel.LookupName}"/>
        </Border>
        <Border Padding="2">
            <StackPanel HorizontalAlignment="Left">
                <lookupPageControl:LookupPage DataContext="{Binding SelectedLookupPage}" />
            </StackPanel>
        </Border>
    </DockPanel>
</Grid>

父母的数据源来自背后的代码（我有理由这样做，不要判断我:)）视图模型层次结构如此（父VM是根）：

+ SelectedLookups : SelectedLookupsViewModel
+-- SelectedLookupPage : LookupPageViewModel
    |-- Lookup : LookupViewModel
    +-- LookupSchema : LookupSchemaViewModel
        +-- LookupAxisLabel : IEnumerable<LookupAxisLabelViewModel>
            |-- Label : String
            +-- LookupAxis : LookupAxisViewModel
                |-- LookupAxisIndex : IList<LookupAxisIndexViewModel>
                +-- SelectedLookupAxisIndexViewModel : LookupAxisIndexViewModel
                    |--- LookupAxisIndexId : int
                    |--- DisplayName : string
                    |--- SequenceNumber : int

其中，子级UC属性 DataContext 已用作嵌入式VM的网关（父级包含子级VM）。

My Child用户控件使用 SelectedLookupPage 属性，并将绑定地图数据从VM映射到控件（一切正常，所有数据都显示）：

<UserControl x:Class="LookupPageControl.LookupPage"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:viewModels="clr-namespace:PELookup.ViewModels;assembly=PELookup"
         mc:Ignorable="d" 
         d:DesignMinHeight="100" d:DesignMinWidth="320" >
<UserControl.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="Resources/Converters.xaml"/>
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
</UserControl.Resources>
<DockPanel>
    <StackPanel>
        <Grid VerticalAlignment="Center">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <RadioButton Padding="5,0,5,0" Margin="5,10,0,0" Name="SelectFileRBtn" Grid.Column="0" GroupName="Option1" VerticalAlignment="Center" Content="Select file to import"  Grid.Row="1" IsChecked="{Binding SelectedLookupHandlingOption, Converter={StaticResource BoolToLookupPageSelectedTypeEnum}, Mode=TwoWay, ConverterParameter=SelectedFileToImport}" />
            <RadioButton Padding="5,0,5,0" Margin="5,10,0,0" Name="OnePropRBtn" Grid.Column="0" GroupName="Option2" VerticalAlignment="Center" Content="Change one property" Grid.Row="5" IsChecked="{Binding SelectedLookupHandlingOption, Converter={StaticResource BoolToLookupPageSelectedTypeEnum}, Mode=TwoWay, ConverterParameter=ChangeOneProperty}" />
            <TextBox Grid.Column="0" Margin="15,10,0,0" Grid.Row="2" Width="200" HorizontalAlignment="Left" IsEnabled="{Binding IsEnabledSelectFile}" Name="FilePathTxt" Text="{Binding FilePath, UpdateSourceTrigger=PropertyChanged}" />
            <Button Grid.Column="1" Margin="0,10,5,0" Grid.Row="2" Width="100" HorizontalAlignment="Left" IsEnabled="{Binding IsEnabledSelectFile}" Click="Button_Click" >Open File</Button>
            <Button Grid.Column="2" Margin="0,10,5,0" Grid.Row="2" Width="100" HorizontalAlignment="Left" IsEnabled="{Binding IsSendButtonEnabled}" Command="{Binding SendFileCmd}" >Send</Button>
            <GroupBox Visibility="{Binding ProgressBarGroupVisibility}" Margin="5,10,5,0" Header="Lookup file upload" Grid.Row="3" Grid.ColumnSpan="3" Grid.Column="0">
                <WrapPanel Margin="5"  >

                    <ProgressBar Margin="0,5,0,5" HorizontalAlignment="Stretch" Orientation="Horizontal" Visibility="Visible" Height="10" IsIndeterminate="{Binding IsFileSendProgressBarIsIndeterminate}" 
                              Minimum="0" Maximum="100" Value="{Binding FileSendProgressBarValue}" Width="300" Name="FileSendProgressBar" />
                    <Image Margin="10,0,0,0" Visibility="{Binding ElementName=FileSendProgressBar, Path=Value, Converter={StaticResource IntToVisibilityConverter}, Mode=OneWay}" Source="{Binding IsFileSentSuccess, Converter={StaticResource BoolToPathFileSuccFailConverter}}" Height="30" />

                </WrapPanel>
            </GroupBox>
            <GroupBox Visibility="{Binding IsFileSentSuccess, Converter={StaticResource BoolToVisibilityCollapsedConverter}}" Margin="5,5,5,0" Header="Lookup processing" Grid.Row="4" Grid.ColumnSpan="3" Grid.Column="0">
                <WrapPanel Margin="5"  >

                <ProgressBar Margin="0,5,0,5" HorizontalAlignment="Stretch" Orientation="Horizontal" Visibility="{Binding IsSendFileProgressBarVisible, Converter={StaticResource BoolToVisibilityConverter}, Mode=OneWay}" Height="10" IsIndeterminate="{Binding IsProgressBarIsIndeterminate}" 
                              Minimum="0" Maximum="100" Value="{Binding ImportedFileProgress}" Width="300" Name="LookupProcessingProgressBar" />
                    <Image Margin="10,0,0,0" Visibility="{Binding ElementName=LookupProcessingProgressBar, Path=Value, Converter={StaticResource IntToVisibilityConverter}, Mode=OneWay}" Source="Images\success.png" Height="30" />

                </WrapPanel>
            </GroupBox>

        </Grid>
        <StackPanel IsEnabled="{Binding IsEnabledChangeOneProp}">
            <GroupBox Margin="5,10,5,0" Header="Lookup Axis">
                <ItemsControl Margin="5,0,5,0" ItemsSource="{Binding Path=LookupSchema.LookupAxisLabel}" >
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition Width="Auto" />
                                </Grid.ColumnDefinitions>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto"/>
                                    <RowDefinition Height="Auto"/>
                                </Grid.RowDefinitions>
                                <Label MinWidth="100" Grid.Column="0" Grid.Row="0" Content="{Binding Label}" VerticalAlignment="Bottom" Padding="5,5,5,0" />
                                <ComboBox MinWidth="100" Grid.Column="1" Grid.Row="0" Height="Auto" Name="cmbName" IsSynchronizedWithCurrentItem="True" 
                                          SelectedItem="{Binding Path=LookupAxis.SelectedLookupAxisIndexViewModel, Mode=TwoWay}"  
                                  ItemsSource="{Binding Path=LookupAxis.LookupAxisIndex}" VerticalAlignment="Top" Padding="5,5,5,0">
                                    <TextSearch.TextPath>DisplayName</TextSearch.TextPath>
                                    <ComboBox.ItemTemplate>
                                        <DataTemplate>
                                            <TextBlock DataContext="{Binding}">
                                                <TextBlock.Text>
                                                    <MultiBinding StringFormat="{}{0}">
                                                        <!--<Binding Path="SequenceNumber" />-->
                                                        <Binding Path="DisplayName" />
                                                    </MultiBinding>
                                                </TextBlock.Text>
                                            </TextBlock>
                                        </DataTemplate>
                                    </ComboBox.ItemTemplate>
                                </ComboBox>
                            </Grid>
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>

            </GroupBox>
            <Button Margin="5,10,5,0" Width="100" HorizontalAlignment="Right" Command="{Binding GetLookupCellsCmd}" IsEnabled="{Binding IsGetLookupDataBtnEnabled}" >Get lookup data</Button>
            <DataGrid Name="CellResultDataGrid" Margin="5,10,5,0" ItemsSource="{Binding Path=LookupCellsResultData}" Visibility="{Binding Path=LookupCellSearchViewModel, Converter={StaticResource NullGridToGridVisibility}}" IsTextSearchEnabled="True" IsTextSearchCaseSensitive="False"
                  CanUserSortColumns="True" CanUserAddRows="False" AutoGeneratingColumn="CellResultDataGrid_AutoGeneratingColumn" />
            <Button Margin="5,10,5,5" Width="100" HorizontalAlignment="Right" Command="{Binding SaveLookupCellsCmd}" IsEnabled="{Binding IsSaveCellBtnEnabled}" Visibility="{Binding ElementName=CellResultDataGrid, Path=Visibility}" >Save</Button>
        </StackPanel>
    </StackPanel>
</DockPanel>

不幸的是，当我调用RelayCommand obj来更新另一个我需要知道项目用户选择的数据的时候，当selectedItem值被更改（VM中的值也被更改）时， value为null

让我想知道，如果嵌入式UC的DataSource属性没有权限拒绝更新作为父VM（嵌入式）的一部分的VM。然后我尝试从后面的代码中加载组件，其中整个父VM被注入到子UC中，我最终得到了相同的行为。出于某些原因，看起来像组合框控制让我的生活更加艰难。

请有人帮助我。

FYI我的方式＆＃34; LookupSchema＆＃34;填充的属性：

 public LookupSchemaViewModel LookupSchema
    {
        get
        {
            if (_lookupSchema == null)
            {
                Task.Run(() => UpdateLookupSchema());
            }

            return _lookupSchema;
        }
        set
        {
            SetProperty(ref _lookupSchema, value);                
        }
    }

当你点击按钮＆＃34;获取查找数据＆＃34;时，另一个命令被用来触发调用＆＃34; GetLookupCells＆＃34;方法如下：

private void GetLookupCells(object obj)
    {
        try
        {
            lock (Lock)
                IsInProgress = true;

            lock (LookupSchema)
            {
                var x =
                    LookupSchema.LookupAxisLabel.FirstOrDefault(
                        axi => axi.LookupAxis.AxiSequenceIndex == (int)LookupAxiSequenceIndexEnum.X);
                var y =
                    LookupSchema.LookupAxisLabel.FirstOrDefault(
                        axi => axi.LookupAxis.AxiSequenceIndex == (int)LookupAxiSequenceIndexEnum.Y);
                var z =
                    LookupSchema.LookupAxisLabel.FirstOrDefault(
                        axi => axi.LookupAxis.AxiSequenceIndex == (int)LookupAxiSequenceIndexEnum.Z);

                LookupCellSearchViewModel = _lookupRestAPIService.GetCellSearch(LookupViewModel.LookupId,
                    x != null ? x.LookupAxis.SelectedLookupAxisIndexViewModel.DisplayName : String.Empty,
                    y != null ? y.LookupAxis.SelectedLookupAxisIndexViewModel.DisplayName : String.Empty,
                    z != null ? z.LookupAxis.SelectedLookupAxisIndexViewModel.DisplayName : String.Empty)
                    .ToLookupCellSearchViewMolel();

                // subscribe on value change to update "save cell value button"
                LookupCellSearchViewModel.LookupCells.ToList().ForEach(item=>item.ToList().ForEach(vm=>vm.PropertyChanged +=
                    (sender, args) => RaisePropertyChanged(() => IsSaveCellBtnEnabled)));
            }
        }
        catch (Exception ex)
        {
            lock (ErrorMessage)
                ErrorMessage = ex.Message;
        }
        finally
        {
            lock (Lock)
                IsInProgress = false;
        }
    }

图片中的样子如下：

Answer 1

通常回答这类问题并不容易，但请尝试检查这些项目并检查其提到的更改：

当您使用ViewModel和Test Axis Combobox以及其他Get lookup data Button和主持人{{1}时，请确保您引用UserControls的一个实例。 }}。
在Window属性中UpdateLookupSchema()使用LookupSchemaViewModel
确保Task.Run文件中的每个已使用属性都属于以下属性之一：
- 在Xaml部分中调用ViewModel的{{1}}的媒体资源。查看this article，它会在OnPropertyChanged类中正确实现Set接口。
- INotifyPropertyChanged
在VM属性和UserControl命令中的用户控件中添加一些括号，以检查单击LookupSchema按钮时的确切情况。

我们在您的问题中没有您的GetLookupCellsCmd课程和其他部分项目，所以当您点击get lookup data时，我们不知道其中发生了什么！

Answer 2

好的，在玩了我的虚拟机后，我发现我的“LookupAxisLabel”集合不是可观察集合的类型。

这一改变之后一切正常。

感谢大家的评论，感谢它。

WPF Combobox SelectedItem数据持久性失败

2 个答案: