C# 设置第二个DataContext时失去DataContext焦点

我有一个带有构造函数的类

TabItemView.xaml.cs

。我在它的

DataContext

中设置为

MainViewModel

，因为在TabItemView中找到了需要绑定数据的DataGrid

public partial class TabItemView : UserControl
{
    public TabItemView()
        {
            InitializeComponent();
            MainViewModel myModel= new MainViewModel();
            this.DataContext = myModel;
        }
    }

在class

MainWindow.xaml.cs

中，我还在按钮单击事件中将

DataContext

设置为

MainViewModel

。此事件在单击按钮时添加新选项卡

 public partial class MainWindow2 : Window
    {
     //Constructor and some other stuf
                 .....
  private void AddInvoice_Click(object sender, RoutedEventArgs e)
    {
        count++;

        string s = string.Format("Tab {0}", count);
        mainViewModel.Items.Add(new ItemViewModel(s));
        this.DataContext = mainViewModel;
    }
}

这是我的

MainViewModel

 public class MainViewModel : ViewModelBase
{
    private ObservableCollection<ItemViewModel> items = new ObservableCollection<ItemViewModel>();
    private ObservableCollection<ItemViewModel> invoice_items = new ObservableCollection<ItemViewModel>();

    public ObservableCollection<ItemViewModel> Invoice_Items
    {
        get
        {
            return invoice_items;
        }
        set
        {
            invoice_items = value;
            OnPropertyChanged("Invoice_Items");
        }
    }

    public ObservableCollection<ItemViewModel> Items
    {
        get
        {
            return items;
        }
        set
        {
            items = value;
            OnPropertyChanged("Items");
        }
    }

    private int _selectedTabIndex;

public int SelectedTabIndex
{
    get { return _selectedTabIndex; }
    set { _selectedTabIndex = value; }
}

public MainViewModel()
{
    SelectedTabIndex = 0;
}


}

这是为

TabItemView

<UserControl x:Class="WPF_AccApp.Views.TabItemView"
         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="640" d:DesignWidth="800" Focusable="True" IsHitTestVisible="True">
    <Grid Name="grid1" HorizontalAlignment="Stretch" VerticalAlignment="Top" MinWidth="768" MinHeight="446" Focusable="True">
        <Grid.RowDefinitions>
            <RowDefinition MinHeight="43" Height="*" />
            <RowDefinition Height="*" MinHeight="45" />
            <RowDefinition Height="*" MinHeight="45" />
            <RowDefinition Height="*" MinHeight="350" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" MinWidth="100" />
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <TextBox Text="{Binding Supplier}" Grid.Column="1" Height="27" Name="textBox1" VerticalAlignment="Top" Margin="11,6,0,0" HorizontalAlignment="Stretch" Width="Auto" FontSize="14" HorizontalContentAlignment="Stretch" MinWidth="141" FlowDirection="LeftToRight" DataContext="{Binding}" />
        <Label Content="Supplier" Height="27" Name="label2" VerticalAlignment="Top" FontSize="14" FontFamily="Tahoma" FontWeight="Bold" Margin="21,6,0,0" Width="Auto" IsEnabled="True" HorizontalAlignment="Stretch" Foreground="Black" Background="White" MinWidth="133" HorizontalContentAlignment="Stretch" />
        <TextBox Text="{Binding SupplierBank}" Grid.Column="1" Grid.Row="1" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,0,0" Name="textBox11" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Row="1" Content="Supplier Bank" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label3" VerticalAlignment="Top" Width="Auto" Background="White" MinWidth="133" />
        <TextBox Text="{Binding SupplierAccount}" Grid.Column="1" Grid.Row="2" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,0,0" Name="textBox12" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Row="2" Content="Account Number" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label4" VerticalAlignment="Top" Background="White" MinWidth="133" />
        <TextBox Text="{Binding Buyer}" Grid.Column="4" FontSize="14" Height="27" Margin="11,6,20,0" Name="textBox2" VerticalAlignment="Top" HorizontalAlignment="Stretch" Width="Auto" MinWidth="141" />
        <Label Grid.Column="3" Content="Buyer" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label5" VerticalAlignment="Top" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch" Background="White" MinWidth="133" />
        <TextBox Text="{Binding BuyerBank}" Grid.Column="4" Grid.Row="1" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,20,0" Name="textBox3" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Column="3" Grid.Row="1" Content="Buyer Bank" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label6" VerticalAlignment="Top" Width="Auto" HorizontalAlignment="Stretch" Background="White" MinWidth="133" />
        <TextBox Text="{Binding BuyerAccount}" Grid.Column="4" Grid.Row="2" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,20,0" Name="textBox4" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Column="3" Grid.Row="2" Content="Account Number" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label7" VerticalAlignment="Top" Width="Auto" HorizontalAlignment="Stretch" Background="White" MinWidth="133" />
    <DataGrid AutoGenerateColumns="False" Grid.ColumnSpan="5" Grid.Row="3" 
              Height="104" HorizontalAlignment="Stretch" Margin="55,115,55,0" Name="dataGrid1" 
              VerticalAlignment="Top" Width="Auto" CanUserResizeRows="True" ItemsSource="{Binding Invoice_Items}"
              IsReadOnly="False" SelectionUnit="Cell" CanUserAddRows="True">
        <DataGrid.Columns>
            <DataGridTextColumn Header="Item Name" Binding="{Binding Item_Name, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Mesure" Binding="{Binding Mesure, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Quantity" Binding="{Binding Quantity, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Price exc VAT" Binding="{Binding Price_exc_VAT, Mode=TwoWay}"/>
            <DataGridTextColumn Header="VAT" Binding="{Binding VAT, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Price Inc VAT" Binding="{Binding Price_inc_VAT, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Total" Binding="{Binding Total, Mode=TwoWay}"/>
        </DataGrid.Columns>
    </DataGrid>
    <TextBox Grid.ColumnSpan="3" Grid.Row="3" Height="27" HorizontalAlignment="Stretch" Name="textBox5" VerticalAlignment="Top" Grid.Column="1" Margin="11,0,0,0" />
    <Label Background="White" Content="Shipping Address" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,0,0,0" MinWidth="133" Name="label1" VerticalAlignment="Top" Grid.Row="3" />
    <Label Background="White" Content="Invoice #" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="78,65,0,0" MinWidth="133" Name="label8" VerticalAlignment="Top" Grid.Column="1" Grid.Row="3" Grid.ColumnSpan="2" HorizontalAlignment="Stretch" />
</Grid>

现在问题来了。当我仅在

主窗口中设置DataContext时

my

文本框

的反应正常，my

ObservableCollection

项目会收到有关更改的通知。当我添加新选项卡时，它会在

文本框

中创建无文本的正常状态

但是，当我在

main窗口

和

TabItemView

中设置DataContext（就像我添加的代码）以通知我的发票项目

observedcollection

有关

DataGrid

中的更改时，这两个

observedcollection

的DataContext都丢失了，它们不再被通知更改。当我添加新选项卡时，它将复制我在

TextBox

s和

DataGrid

中先前选项卡中添加的数据

另外，当我没有在

main窗口中设置DataContext，并且仅在
TabItemView
my
ObservableCollection
Invoice\u中设置DataContext时，项目会收到有关
DataGrid
中更改的通知，但当我添加新选项卡时，
DataGrid
的数据只会在每个添加的选项卡中重复出现

为什么会这样，我做错了什么？我如何解决这个问题？
如果你需要更多的代码或信息，只需说。我正在寻求任何帮助，以了解如何解决我的问题。谢谢您的回答。
DataGrid的数据仅在每个添加的选项卡中重复。因为您为每个包含集合的选项卡设置了相同的ViewModel实例。>>当我在MainWindow和TabItemView中设置DataContext时，您在哪里为
TabItemView
设置了
DataContext
。在TabItemView构造函数中…
DataGrid的
数据只会在每个添加的选项卡中复制。因为您正在为每个包含集合的选项卡设置相同的ViewModel实例。>>当我在MainWindow和TabItemView中设置DataContext时，您在哪里为
TabItemView
设置
DataContext
。在TabItemView构造函数中。。。
<UserControl x:Class="WPF_AccApp.Views.TabItemView"
         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="640" d:DesignWidth="800" Focusable="True" IsHitTestVisible="True">
    <Grid Name="grid1" HorizontalAlignment="Stretch" VerticalAlignment="Top" MinWidth="768" MinHeight="446" Focusable="True">
        <Grid.RowDefinitions>
            <RowDefinition MinHeight="43" Height="*" />
            <RowDefinition Height="*" MinHeight="45" />
            <RowDefinition Height="*" MinHeight="45" />
            <RowDefinition Height="*" MinHeight="350" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" MinWidth="100" />
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <TextBox Text="{Binding Supplier}" Grid.Column="1" Height="27" Name="textBox1" VerticalAlignment="Top" Margin="11,6,0,0" HorizontalAlignment="Stretch" Width="Auto" FontSize="14" HorizontalContentAlignment="Stretch" MinWidth="141" FlowDirection="LeftToRight" DataContext="{Binding}" />
        <Label Content="Supplier" Height="27" Name="label2" VerticalAlignment="Top" FontSize="14" FontFamily="Tahoma" FontWeight="Bold" Margin="21,6,0,0" Width="Auto" IsEnabled="True" HorizontalAlignment="Stretch" Foreground="Black" Background="White" MinWidth="133" HorizontalContentAlignment="Stretch" />
        <TextBox Text="{Binding SupplierBank}" Grid.Column="1" Grid.Row="1" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,0,0" Name="textBox11" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Row="1" Content="Supplier Bank" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label3" VerticalAlignment="Top" Width="Auto" Background="White" MinWidth="133" />
        <TextBox Text="{Binding SupplierAccount}" Grid.Column="1" Grid.Row="2" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,0,0" Name="textBox12" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Row="2" Content="Account Number" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label4" VerticalAlignment="Top" Background="White" MinWidth="133" />
        <TextBox Text="{Binding Buyer}" Grid.Column="4" FontSize="14" Height="27" Margin="11,6,20,0" Name="textBox2" VerticalAlignment="Top" HorizontalAlignment="Stretch" Width="Auto" MinWidth="141" />
        <Label Grid.Column="3" Content="Buyer" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label5" VerticalAlignment="Top" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch" Background="White" MinWidth="133" />
        <TextBox Text="{Binding BuyerBank}" Grid.Column="4" Grid.Row="1" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,20,0" Name="textBox3" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Column="3" Grid.Row="1" Content="Buyer Bank" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label6" VerticalAlignment="Top" Width="Auto" HorizontalAlignment="Stretch" Background="White" MinWidth="133" />
        <TextBox Text="{Binding BuyerAccount}" Grid.Column="4" Grid.Row="2" FontSize="14" Height="27" HorizontalAlignment="Stretch" Margin="11,6,20,0" Name="textBox4" VerticalAlignment="Top" Width="Auto" MinWidth="141" />
        <Label Grid.Column="3" Grid.Row="2" Content="Account Number" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,6,0,0" Name="label7" VerticalAlignment="Top" Width="Auto" HorizontalAlignment="Stretch" Background="White" MinWidth="133" />
    <DataGrid AutoGenerateColumns="False" Grid.ColumnSpan="5" Grid.Row="3" 
              Height="104" HorizontalAlignment="Stretch" Margin="55,115,55,0" Name="dataGrid1" 
              VerticalAlignment="Top" Width="Auto" CanUserResizeRows="True" ItemsSource="{Binding Invoice_Items}"
              IsReadOnly="False" SelectionUnit="Cell" CanUserAddRows="True">
        <DataGrid.Columns>
            <DataGridTextColumn Header="Item Name" Binding="{Binding Item_Name, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Mesure" Binding="{Binding Mesure, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Quantity" Binding="{Binding Quantity, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Price exc VAT" Binding="{Binding Price_exc_VAT, Mode=TwoWay}"/>
            <DataGridTextColumn Header="VAT" Binding="{Binding VAT, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Price Inc VAT" Binding="{Binding Price_inc_VAT, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Total" Binding="{Binding Total, Mode=TwoWay}"/>
        </DataGrid.Columns>
    </DataGrid>
    <TextBox Grid.ColumnSpan="3" Grid.Row="3" Height="27" HorizontalAlignment="Stretch" Name="textBox5" VerticalAlignment="Top" Grid.Column="1" Margin="11,0,0,0" />
    <Label Background="White" Content="Shipping Address" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="21,0,0,0" MinWidth="133" Name="label1" VerticalAlignment="Top" Grid.Row="3" />
    <Label Background="White" Content="Invoice #" FontFamily="Tahoma" FontSize="14" FontWeight="Bold" Height="27" Margin="78,65,0,0" MinWidth="133" Name="label8" VerticalAlignment="Top" Grid.Column="1" Grid.Row="3" Grid.ColumnSpan="2" HorizontalAlignment="Stretch" />
</Grid>