WPF DataGrid 未填充来自 viewmodel 的信息（DataBinding 不工作）

Question

我有一个名为 TagGridView 的 UserControl 和一个相应的 TagGridViewModel，它包含一个 ObservableCollection<TagViewModel>，使用数据绑定显示在 DataGrid 中。 TagViewModel 公开了一些我试图在 DataGrid 中显示的属性。

我创建了一个按钮，用于将项目添加到 ObservableCollection<TagViewModel> 并显示一个消息框，其中包含集合的项目计数和数据网格的项目计数。该集合正在获取所有项目，除了 DataGrid 始终表示其计数为 0。

这是带有数据绑定的 XAML 代码：

<UserControl x:Class="Company.TagVisualizer.Views.TagGridView"
             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" Width="Auto" Height="Auto" Name="TagGrid" DataContext="{Binding Source=TagGridContext}">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <DataGrid Name="DataGridTag" Grid.Column="0" Grid.Row="0" ItemsSource="{Binding Path=TagsCollection}" Margin="0" CanUserReorderColumns="False" CanUserResizeColumns="True" CanUserAddRows="True" CanUserDeleteRows="True">
            <DataGrid.Columns>
                <DataGridCheckBoxColumn Width="*"  Header="Selected" />
                <DataGridTextColumn Width="3*" Binding="{Binding Path=TagName}" Header="Tag Name"/>
                <DataGridTextColumn Width="3*" Binding="{Binding Detections.Count}" Header="Detections"/>
                <DataGridTextColumn Width="3*" Binding="{Binding EarliestDetection}"  Header="Earliest Detection"/>
                <DataGridTextColumn Width="3*" Binding="{Binding LatestDetection}" Header="Latest Detection"/>
            </DataGrid.Columns>
        </DataGrid>
        <Button Grid.Column="0" Grid.Row="1" Content="Add" Click="Add_OnClick"/>
    </Grid>

</UserControl>

这是 TagGridView 的代码隐藏文件：

public partial class TagGridView : UserControl
    {
        private TagGridViewModel _tagGridViewModel = new TagGridViewModel();

        public TagGridView()
        {
            InitializeComponent();

        }

        public TagGridViewModel TagGridContext { get { return _tagGridViewModel; } set { _tagGridViewModel = value; } }

        private void Add_OnClick(object sender, RoutedEventArgs e)
        {
            TagGridContext.TagsCollection.Add(new TagViewModel("Boogie", 134.5, 145.8));

            MessageBox.Show(string.Format("Items in collection: {0}\nItems in Grid: {1}", TagGridContext.TagsCollection.Count, DataGridTag.Items.Count));
        }
    }

这里是 TagGridViewModel class:

public class TagGridViewModel
    {
        private ObservableCollection<TagViewModel> _tagsCollection = new ObservableCollection<TagViewModel>();

        public ObservableCollection<TagViewModel> TagsCollection
        {
            get { return _tagsCollection; }
            set
            {
                _tagsCollection = value;
            }
        }
    }

我不确定发生了什么。我尝试在 UserControl 标签和 DataGrid 标签中设置 DataContext。无论我做什么，DataGrid 都不会向自身添加任何项目。

Answer 1

是用户控件数据上下文问题。请参考下面的数据绑定代码。

<UserControl x:Class="Tags_Learning.TagGridView"
         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:DesignHeight="300" d:DesignWidth="300" **DataContext="{Binding Path=TagGridContext, RelativeSource={RelativeSource Self}}"**>
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition/>
    </Grid.RowDefinitions>
    <DataGrid Name="DataGridTag" Grid.Column="0" Grid.Row="0" ItemsSource="{Binding Path=TagsCollection}" Margin="0" 
              CanUserReorderColumns="False" CanUserResizeColumns="True" CanUserAddRows="True" CanUserDeleteRows="True">
        <DataGrid.Columns>
            <DataGridCheckBoxColumn Width="*"  Header="Selected" />
            <DataGridTextColumn Width="3*" Binding="{Binding Path=TagName}" Header="Tag Name"/>                
            <DataGridTextColumn Width="3*" Binding="{Binding EarliestDetection}"  Header="Earliest Detection"/>
            <DataGridTextColumn Width="3*" Binding="{Binding LatestDetection}" Header="Latest Detection"/>
        </DataGrid.Columns>
    </DataGrid>
    <Button Grid.Column="0" Grid.Row="1" Content="Add" Click="Add_OnClick"/>
</Grid>

WPF DataGrid 未填充来自 viewmodel 的信息（DataBinding 不工作）

WPF DataGrid not populating with information from viewmodel (DataBinding not working)

wpf

xaml

mvvm

datagrid