C＃WPF OneWayToSource绑定未按预期工作

Question

我的xaml文件中有以下代码：

<WrapPanel Grid.Row="0" HorizontalAlignment="Center" Margin="10">
            <Label Content="Azonosító:"/>
            <TextBox x:Name="txtId" Width="80" IsEnabled="False" Text="{Binding Path=SelectedStudent.Id, Mode=TwoWay}"/>
            <Label Content="Név:"/>
            <TextBox x:Name="txtName" Width="100" Text="{Binding Path=SelectedStudent.Name, Mode=TwoWay}"/>
            <Label Content="Cím:"/>
            <TextBox x:Name="txtAddress" Width="150" Text="{Binding Path=SelectedStudent.Address, Mode=TwoWay}"/>
            <Label Content="Kar:"/>
            <TextBox x:Name="txtFaculty" Width="50" Text="{Binding Path=SelectedStudent.Faculty, Mode=TwoWay}"/>
        </WrapPanel>

...

<DataGrid x:Name="dgdStudents" Grid.Row="1" Background="White" BorderBrush="LightGray" CanUserAddRows="False" 
              CanUserDeleteRows="False" CanUserReorderColumns="False" Cursor="Hand"
              ItemsSource="{Binding Students}" AutoGenerateColumns="False" IsReadOnly="True" SelectionMode="Single" 
              SelectionUnit="FullRow" SelectedItem="{Binding SelectedStudent, Mode=OneWayToSource}">

正如您所看到的，我在WrapPanel中将SelectedStudent与TwoWay模式绑定，并在DataGrid中绑定OneWayToSource模式。但是，每当我在数据网格中选择一行并修改文本框中的值时，所选行也会根据修改而更改。为什么呢？