UserControls中控件的大小

Question

在我的应用程序中，我有几个UserControl。一个是显示所有人。因此，我有以下UserControl，它显示在我的MainWindow的内容部分中：

<UserControl x:Class="ScM.Contents.View.PersonssView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:viewModel="clr-namespace:ScM.Contents.ViewModel"
             xmlns:view="clr-namespace:ScM.Contents.View"
             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">
    <UserControl.DataContext>
        <viewModel:PersonsViewModel />
    </UserControl.DataContext>
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="200" />
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <view:PersonsTreeView Grid.Column="0" Margin="2"
                         OpenPerson="{Binding DataContext.OpenPersonCommand, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}}"
                         Persons="{Binding DataContext.Persons, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, 
        RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}}" />
    <GridSplitter Grid.Column="1" Width="2" ShowsPreview="True" VerticalAlignment="Stretch"
                  HorizontalAlignment="Center" Margin="0,2" />
        <DockPanel LastChildFill="True" Grid.Column="2"  Margin="2">
            <ContentControl Content="{Binding CurrentContent, UpdateSourceTrigger=PropertyChanged}" 
                    HorizontalAlignment="Stretch" VerticalAlignment="Stretch" MinWidth="400"/>
        </DockPanel>
</Grid>

如果用户点击了PersonsTreeView中的TreeViewItem，则应在UserControl中显示另一个ContentControl。

UserControl中显示的ContentControl称为PersonView，看起来像

 <UserControl x:Class="ScM.Contents.View.PersonView"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:viewModel="clr-namespace:ScM.Contents.ViewModel"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<UserControl.DataContext>
    <viewModel:PersonViewModel/>
</UserControl.DataContext>
<TabControl>
        <TabItem Header="Personal">
            <GroupBox Header="Name">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition Width="*"/>
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="Auto"/>
                    </Grid.RowDefinitions>
                    <Label Grid.Row="0" Grid.Column="0" Content="Firstname:"/>
                    <TextBox Grid.Row="0" Grid.Column="1"></TextBox>
                    <Label Grid.Row="1" Grid.Column="0" Content="Lastname:"/>
                    <TextBox Grid.Row="1" Grid.Column="1"></TextBox>                
                </Grid>
            </GroupBox>
        </TabItem>
    </TabControl>

我现在的问题是，PersonView中的控件非常小（因此也是AutoSize）。我以为他们会*（最大）。

我做错了什么？