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C# WPF XAML Toolkit, switch views with button click

I am using Material Design in XAML Toolkit. I have the main window with drawer, which contains the list of user controls (app tabs). When I click on them - application tab switches between this controls. I want to add a button to the window, and when I click on it I want to switch between tabs too. You can see important parts of my code here:
<materialDesign:DialogHost Identifier="RootDialog" SnackbarMessageQueue="{Binding ElementName=MainSnackbar, Path=MessageQueue}">
<materialDesign:DrawerHost IsLeftDrawerOpen="{Binding ElementName=MenuToggleButton, Path=IsChecked}">
<materialDesign:DrawerHost.LeftDrawerContent>
<DockPanel MinWidth="212">
<ToggleButton Style="{StaticResource MaterialDesignHamburgerToggleButton}"
DockPanel.Dock="Top"
HorizontalAlignment="Right" Margin="16"
IsChecked="{Binding ElementName=MenuToggleButton, Path=IsChecked, Mode=TwoWay}" />
<ListBox x:Name="DemoItemsListBox" Margin="0 16 0 16" SelectedIndex="0"
ItemsSource="{Binding DemoItems}"
PreviewMouseLeftButtonUp="UIElement_OnPreviewMouseLeftButtonUp">
<ListBox.ItemTemplate>
<DataTemplate DataType="helpers:DemoItem">
<TextBlock Text="{Binding Name}" Margin="32 0 32 0" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</DockPanel>
</materialDesign:DrawerHost.LeftDrawerContent>
<DockPanel>
<materialDesign:ColorZone Padding="16" materialDesign:ShadowAssist.ShadowDepth="Depth2"
Mode="PrimaryDark" DockPanel.Dock="Top">
<DockPanel>
<ToggleButton Style="{StaticResource MaterialDesignHamburgerToggleButton}" IsChecked="False"
x:Name="MenuToggleButton"/>
<materialDesign:PopupBox x:Name="popupBox">
<TextBlock>Check me please</TextBlock>
</materialDesign:PopupBox>
<CheckBox x:Name="LizenzeCheckBox" DockPanel.Dock="Right" Style="{StaticResource MaterialDesignCheckBox}" Tag="False">
<CheckBox.IsChecked>
<Binding Path="Tag" RelativeSource="{RelativeSource Self}">
<Binding.ValidationRules>
<helpers:IsCheckedValidationRule />
</Binding.ValidationRules>
</Binding>
</CheckBox.IsChecked>CheckBox text</CheckBox>
<TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="22">My App</TextBlock>
</DockPanel>
</materialDesign:ColorZone>
<Button x:Name="TheBUTTON" Click="Button_Click">Ckicc</Button>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<ScrollViewer Grid.Row="1"
HorizontalScrollBarVisibility="{Binding ElementName=DemoItemsListBox, Path=SelectedItem.HorizontalScrollBarVisibilityRequirement}"
VerticalScrollBarVisibility="{Binding ElementName=DemoItemsListBox, Path=SelectedItem.VerticalScrollBarVisibilityRequirement}"
Padding="{Binding ElementName=DemoItemsListBox, Path=SelectedItem.MarginRequirement}">
<ContentControl Content="{Binding ElementName=DemoItemsListBox, Path=SelectedItem.Content}" />
</ScrollViewer></Grid>
This is my main window xaml code, as you can see, I bind ListBox Values to DemoItem[] array from viewModel. "TheButton" onclick event is the event which I want to use for tab switching.
My main window view model is:
public class MainWindowViewModel
{
public DemoItem[] DemoItems { get; }
public MainWindowViewModel(ISnackbarMessageQueue snackbarMessageQueue)
{
if (snackbarMessageQueue == null) throw new ArgumentNullException(nameof(snackbarMessageQueue));
DemoItems = new[]
{
new DemoItem("Tab1", new Tab1()),
new DemoItem("Tab2", new Tab2()),
new DemoItem("Tab3", new Tab3()),
};
}
}
The MainWindow.cs is:
public partial class MainWindow : Window
{
public static Snackbar Snackbar;
public MainWindow()
{
InitializeComponent();
Task.Factory.StartNew(() =>
{
Thread.Sleep(1000);
}).ContinueWith(t =>
{
MainSnackbar.MessageQueue.Enqueue("Welcome to my app");
}, TaskScheduler.FromCurrentSynchronizationContext());
DataContext = new MainWindowViewModel(MainSnackbar.MessageQueue);
}
private void UIElement_OnPreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
//until we had a StaysOpen glag to Drawer, this will help with scroll bars
var dependencyObject = Mouse.Captured as DependencyObject;
while (dependencyObject != null)
{
if (dependencyObject is ScrollBar) return;
dependencyObject = VisualTreeHelper.GetParent(dependencyObject);
}
MenuToggleButton.IsChecked = false;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
//what to do here?
}
}
The DemoItem Class is:
public class DemoItem : INotifyPropertyChanged
{
private string _name;
private object _content;
private ScrollBarVisibility _horizontalScrollBarVisibilityRequirement;
private ScrollBarVisibility _verticalScrollBarVisibilityRequirement;
private Thickness _marginRequirement = new Thickness(16);
public DemoItem(string name, object content)
{
_name = name;
Content = content;
}
public string Name
{
get { return _name; }
set { this.MutateVerbose(ref _name, value, RaisePropertyChanged()); }
}
public object Content
{
get { return _content; }
set { this.MutateVerbose(ref _content, value, RaisePropertyChanged()); }
}
public ScrollBarVisibility HorizontalScrollBarVisibilityRequirement
{
get { return _horizontalScrollBarVisibilityRequirement; }
set { this.MutateVerbose(ref _horizontalScrollBarVisibilityRequirement, value, RaisePropertyChanged()); }
}
public ScrollBarVisibility VerticalScrollBarVisibilityRequirement
{
get { return _verticalScrollBarVisibilityRequirement; }
set { this.MutateVerbose(ref _verticalScrollBarVisibilityRequirement, value, RaisePropertyChanged()); }
}
public Thickness MarginRequirement
{
get { return _marginRequirement; }
set { this.MutateVerbose(ref _marginRequirement, value, RaisePropertyChanged()); }
}
public event PropertyChangedEventHandler PropertyChanged;
private Action<PropertyChangedEventArgs> RaisePropertyChanged()
{
return args => PropertyChanged?.Invoke(this, args);
}
}
My MutateVerbose function looks like:
public static void MutateVerbose<TField>(this INotifyPropertyChanged instance, ref TField field, TField newValue, Action<PropertyChangedEventArgs> raise, [CallerMemberName] string propertyName = null)
{
if (EqualityComparer<TField>.Default.Equals(field, newValue)) return;
field = newValue;
raise?.Invoke(new PropertyChangedEventArgs(propertyName));
}
I don't know how to switch tabs with button click in this situation. Help me, please!

Data Binding does not Update on Property Change (UWP)

I am developing an application using c# and the Universal Windows Platform (UWP) and am struggling with creating a one-way data-bind between a layout control and an observable class. Currently, when the observable class property is changed, it does not update the UI element. I think it has something to do with the fact that I am binding a DataTemplate ListViewItem rather than a static layout element, but I am not sure if this is the problem or how to solve it. Any help would be appreciated. The code for the UI element and backend code is shown.
DataTemplate (XAML) (Styling is removed for readability)
<DataTemplate x:Key="variableTemplate"
x:DataType="local:VariableNode">
<Border>
<StackPanel Orientation="Vertical">
<Border>
<Grid>
<TextBlock Text="{Binding Name}" />
<StackPanel Orientation="Horizontal" >
<Button Tag="{Binding Description}"/>
<Button Tag="{Binding}"/>
</StackPanel>
</Grid>
</Border>
<Grid Margin="0, 10">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"/>
<ColumnDefinition Width="1*"/>
</Grid.ColumnDefinitions>
<Border >
<Grid Grid.Column="0">
<Button Click="Choose_Measurement"
Tag="{Binding}">
<StackPanel Orientation="Vertical">
<TextBlock Text="{x:Bind Path=Measurement_Name, Mode=TwoWay}"
Foreground="{x:Bind MF}" />
<TextBlock Foreground="{x:Bind MF}" />
</StackPanel>
</Button>
</Grid>
</Border>
<Grid Grid.Column="1">
<Button Foreground="{Binding UF}"
Tag="{Binding}"
IsEnabled="{Binding Unit_Exists}"
Click="Choose_Unit">
<StackPanel Orientation="Vertical">
<TextBlock Text="{x:Bind Path=Unit_Name, Mode=OneWay}"
Foreground="{Binding UF}" />
<TextBlock Foreground="{Binding UF}" />
</StackPanel>
</Button>
</Grid>
</Grid>
</StackPanel>
</Border>
</DataTemplate>
C# Observable Class VariableNode (Irrelevant properties removed)
public class VariableNode : ExperimentNode
{
public VariableNode() { }
public VariableNode(VariableType type)
{
Type = type;
Name = name_ref[(int)Type];
Category = "Problem";
Unit = -1;
}
private string[] name_ref = { "Independent Variable", "Dependent Variable", "Controlled Variable" };
public enum VariableType { Independent, Dependent, Controlled };
public VariableType Type { get; set; }
public Measurement Measure { get; set; }
public int Unit { get; set; }
[XmlIgnoreAttribute]
public Measurement MeasureSource
{
get { return this.Measure; }
set
{
this.Measure = value;
OnPropertyChanged("Measurement_Name");
}
}
[XmlIgnoreAttribute]
public string Measurement_Name
{
get
{
if (Measure == null) { return "Select a Measurement"; }
else { return Measure.Name; }
}
set
{
if (Measure != null)
{
Measure.Name = value;
OnPropertyChanged();
}
}
}
[XmlIgnoreAttribute]
public string Unit_Name
{
get
{
if (Measure == null) { return "No measurement"; }
else if (Unit < 0) { return "Select a unit"; }
else { return Measure.Unit[Unit]; }
}
}
[XmlIgnoreAttribute]
public bool Unit_Exists
{
get { return Measure != null; }
}
}
C# XAML.CS code calling the property change
public void Choose_Measurement (object sender, RoutedEventArgs e)
{
Button butt = sender as Button
VariableNode sel = butt.Tag as VariableNode;
sel.Measurement_Name = "New Name";
}
Again thanks for the help, I know its a lot of code, and I appreciate the help in debugging / learning.

Ok, so I ended up finding the answer, and I think that it may help others trying to replicate what I am trying to do:
Basically, the class that one is trying to make observable must extend the class INotifyPropertyChanged. So, I ended up making a base class from which to extend all of my observable classes from:
public class BaseClass : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
protected void OnPropertyChanged(PropertyChangedEventArgs e)
{
PropertyChanged(this, e);
}
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
}

Change item checkbox on ListBox selection change

I have a ListBox created by ItemTemplate and Binding
<controls:PanoramaItem Header="{Binding AppResources.SettingsSubpage2, Source={StaticResource LocalizedStrings}}" HeaderTemplate="{StaticResource HeaderTemplate}">
<Grid>
<ListBox x:Name="DayOfWeekSelector" ItemTemplate="{StaticResource DayOfWeekTemplate}" ItemsSource="{Binding DayOfWeekElementList}" Foreground="{StaticResource AppForegroundColor}" LostFocus="DayOfWeekSelector_LostFocus" HorizontalAlignment="Left" Width="420" />
</Grid>
</controls:PanoramaItem>
Template code:
<phone:PhoneApplicationPage.Resources>
<!--- ... --->
<DataTemplate x:Key="DayOfWeekTemplate">
<Grid Height="65" Width="332">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="60"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<CheckBox IsChecked="{Binding IsActive, Mode=TwoWay}" Tag="{Binding}" d:LayoutOverrides="Width, Height" BorderBrush="{StaticResource AppBackgroundColor}" Background="{StaticResource ScheduleBackgroundAccentsColor}" Grid.Column="0" Unchecked="CheckBox_Unchecked" />
<StackPanel Grid.Column="1" Orientation="Horizontal">
<TextBlock Text="{Binding Name}" VerticalAlignment="Center" d:LayoutOverrides="Width"/>
<TextBlock Text="{Binding TaskCounter, Mode=OneWay, Converter={StaticResource DayOfWeekCounter}}" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="10,0,0,0"/>
</StackPanel>
</Grid>
</DataTemplate>
<!--- ... --->
And it's working fine. I've got all my items on the list. Checkboxes are binded to appropriate elements (clicking on it is changing proper value).
But by default ListBox can be also selected. Selection high-light TextBox binded to Name but don't change CheckBox (binded to IsActive). How can I tie item selection changing to checkbox state changing (in Silverlight)?
Edit:
public partial class SettingsPage : PhoneApplicationPage, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
public List<DayOfWeekElement> DayOfWeekList
{
get
{
return CyberSyncPlanBase.Instance.DayOfWeekElementList;
}
set
{
CyberSyncPlanBase.Instance.DayOfWeekElementList = value;
NotifyPropertyChanged("DayOfWeekList");
}
}
public SettingsPage()
{
InitializeComponent();
DayOfWeekSelector.DataContext = CyberSyncPlanBase.Instance;
}
private void DayOfWeekSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
DayOfWeekElement dowe = (DayOfWeekElement) DayOfWeekSelector.SelectedItem;
if (dowe != null)
dowe.IsActive = (dowe.IsActive) ? false : true;
}
And in singleton INotifyPropertyChanged i've implemented in the same way:
private List<DayOfWeekElement> dayOfWeekElementList;
public List<DayOfWeekElement> DayOfWeekElementList
{
get { return dayOfWeekElementList; }
set
{
dayOfWeekElementList = value;
RecalcWeekTasks();
NotifyPropertyChanged("DayOfWeekElementList");
}
}
Bottom class:
public class DayOfWeekElement
{
public string Name { get { return this.DayOfWeek.ToStringValue(); } }
public bool IsNotEmpty { get { return (TaskCounter > 0); } }
public int TaskCounter { get; set; }
public bool IsActive { get; set; }
public DayOfWeek DayOfWeek { get; set; }
}

I think you could use the SelectedItem property of the ListBox control.
A possible implementation could be this:
Subscribe to the event SelectedIndexChanged of the ListBox.
Get the selected item.
For the selected item, change its IsActive property to true.
This works if the interface INotifyPropertyChanged is implemented in your data class.
E.g.:
public class DayOfWeekElement : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
private bool isActive = false;
public bool IsActive {
get
{
return this.isActive;
}
set
{
if (value != this.isActive)
{
this.isActive= value;
NotifyPropertyChanged("IsActive");
}
}
}
}

How to represent hierarchical DATA using HierarchicalDataTemplate in wpf

I am using MVVM and trying to represent my ViewModel data in View.
I have a class called Track containing list of Variations. I want to represent each variation as a TextBlock using data binding.
I am able to represent a single track as:
<Window.Resources>
<src:Track x:Key="trck"/>
...
</Window.Resources>
<StackPanel DataContext="{Binding Source={StaticResource trck}}" Orientation="Horizontal">
<ItemsControl ItemsSource="{Binding Vars}" Height="53" Width="349">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Background="{Binding Path=color}" Height="15" Width="{Binding Path=elapsedtime}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
I also have a class called TrackList containing collection of Tracks.
I tried to use HierarchicalDataTemplate to represent Hierarchical Data of TrackList.
But it's not working..
I am new to WPF, and I have tried the below things so far:
<DockPanel.Resources>
<DataTemplate DataType="{x:Type src:Variation}">
<TextBlock Background="{Binding Path=color}" Height="15" Width="{Binding Path=elapsedtime}"/>
</DataTemplate>
<HierarchicalDataTemplate DataType = "{x:Type src:Track}" ItemsSource = "{Binding Path=Vars}">
<StackPanel/>
</HierarchicalDataTemplate>
</DockPanel.Resources>
public class TrackList : ViewModel
{
private ICollection<Track> tracks;
private Track selectedTrack;
public string Name
{ get; set; }
public TrackList()
{
this.tracks = new List<Track>();
this.tracks.Add(new Track("T1"));
this.tracks.Add(new Track("T2"));
Name = "Track List";
selectedTrack = tracks.ElementAt(1);
}
public ICollection<Track> Tracks
{
get { return this.Tracks; }
set { this.Tracks = value; }
}
public Track SelectedTrack
{
get { return this.selectedTrack; }
set
{
if (this.selectedTrack != value)
{
this.selectedTrack = value;
this.OnPropertyChanged("SelectedTrack");
}
}
}
}
public class Track : ViewModel
{
private ICollection<Variation> vars;
private Variation selectedVar;
public string Name { get; set; }
public Track()
{
Init();
}
public Track(string p)
{
// TODO: Complete member initialization
this.Name = p;
Init();
}
private void Init()
{
this.vars = new List<Variation>();
this.vars.Add(new Variation("var1", 20, Brushes.Red));
this.vars.Add(new Variation("var2", 60, Brushes.Green));
this.vars.Add(new Variation("var3", 40, Brushes.Khaki));
this.vars.Add(new Variation("var4", 120, Brushes.Aqua));
selectedVar = vars.ElementAt(1);
}
public ICollection<Variation> Vars
{
get { return this.vars; }
set { this.vars = value; }
}
public Variation SelectedVar
{
get { return this.selectedVar; }
set
{
if (this.selectedVar != value)
{
this.selectedVar = value;
this.OnPropertyChanged("SelectedVar");
}
}
}
}
public class Variation : ViewModel
{
public int elapsedtime { get; set; }
public string Name { get; set; }
public System.Windows.Media.Brush color { get; set; }
public Variation(string varname)
{
Name = varname;
}
public Variation(string name, int time, System.Windows.Media.Brush br)
{
// TODO: Complete member initialization
this.Name = name;
this.elapsedtime = time;
this.color = br;
}
}
public abstract class ViewModel : INotifyPropertyChanged
{
private readonly Dispatcher _dispatcher;
protected ViewModel()
{
}
public event PropertyChangedEventHandler PropertyChanged;
protected Dispatcher Dispatcher
{
get { return _dispatcher; }
}
protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
{
PropertyChanged(this, e);
}
protected void OnPropertyChanged(string propertyName)
{
OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
}
Please let me know for any farther information.
Thanks

I don't think you need HierarchicalDataTemplate, your tree has known number of levels (TrackList>Track>Variation). You can simply do this:
<DockPanel.Resources>
<DataTemplate DataType="{x:Type src:Variation}">
<TextBlock Background="{Binding Path=color}" Height="15" Width="{Binding Path=elapsedtime}"/>
</DataTemplate>
<DataTemplate DataType="{x:Type src:Track}">
<StackPanel>
<TextBlock Text="{Binding Name}"/>
<ItemsControl ItemsSource="{Binding Vars}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
</StackPanel>
</DataTemplate>
</DockPanel.Resources>
<ItemsControl ItemsSource="{Binding Tracks}" />
Where ItemsControl bind to Tracks property of the TrackList (ItemsControl.DataContext = TrackList).

You can represent your hierarchical data using a TreeView:
<TreeView ItemsSource="{Binding Tracks}">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type src:Track}" ItemsSource="{Binding Vars}">
<TextBlock Text="{Binding Name}" />
</HierarchicalDataTemplate>
</TreeView.Resources>
</TreeView>

binding not working windows phone 7

hi guys am trying to bind some data.
i have a list of people . on tap of each of these i take the user to details page.
on tap of each item i get the data from the web and parse it.
public ObservableCollection<ItemViewModel> PeopleDetails { get; set; }
the above line i have declared in my MainViewModel
ItemViewModel.cs
public class ItemViewModel : INotifyPropertyChanged
{
private string _person_name;
public string _Person_name
{
get { return _person_name; }
set
{
if (value != _person_name)
{
_person_name= value;
NotifyPropertyChanged("_Person_name");
}
}
}
private string _person_info;
public string _Person_info
{
get { return _person_info; }
set
{
if (value != _person_info)
{
_person_info= value;
NotifyPropertyChanged("_Person_info");
}
}
}
private string _person_image_link;
public string _Person_image_link
{
get { return _person_image_link; }
set
{
if (value != _person_image_link)
{
_person_image_link= value;
NotifyPropertyChanged("_Person_image_link");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
on tap of each item am executing the following code
private void getPeopleDetails(object sender, SelectionChangedEventArgs e)
{
// Navigate to the new page
if (e.AddedItems != null && e.AddedItems.Count == 1)
{
People selectedItem = (People)e.AddedItems[0];
NavigationService.Navigate(new Uri("/PeopleDetailsView.xaml?id="+selectedItem.id, UriKind.Relative));
}
}
then in PeopleDetailsView.xaml.cs my code is as follows
public PeopleDetailsView()
{
DataContext = App.Model;
InitializeComponent();
Loaded+=new RoutedEventHandler(PeopleDetailsView_Loaded);
}
private void PeopleDetailsView_Loaded(Object sender ,RoutedEventArgs e){
string id = "";
if (NavigationContext.QueryString.TryGetValue("id",out id))
{
string url = "*****&id=" + id;";
WebClient client = new WebClient();
client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompletedC);
client.DownloadStringAsync(new Uri(url));
}
}
private void client_DownloadStringCompletedC(object sender, DownloadStringCompletedEventArgs e)
{
try
{
JToken a = JObject.Parse(e.Result);
App.Model.PeopleDetails.Add(
new ItemViewModel()
{
_Person_info = a.SelectToken("info").ToString(),
_Person_image_link = a.SelectToken("image_link").ToString(),
_Person_name = a.SelectToken("name").ToString(),
}
);
}
catch (Exception execp)
{
MessageBox.Show(execp.Message.ToString());
}
}
and finally am binding the data in my PeopleDetailsView.xaml as follows
<Grid x:Name="ContentPanel" DataContext="{Binding PeopleDetails}" Grid.Row="1" Margin="12,0,12,0">
<Grid.RowDefinitions>
<RowDefinition Height="269*" />
<RowDefinition Height="338*" />
</Grid.RowDefinitions>
<Image Height="250" HorizontalAlignment="Left" Margin="12,6,0,0" Name="image1" Stretch="Fill" Source="{Binding _Person_image_link}" VerticalAlignment="Top" Width="246" />
<ScrollViewer Grid.Row="1" Height="274" HorizontalAlignment="Left" Margin="12,42,0,0" Name="scrollViewer1" VerticalAlignment="Top" Width="420">
<TextBlock Height="264" Name="textBlock1" Text="{Binding _Person_info}" />
</ScrollViewer>
</Grid>
</Grid>
but in the PeopleDetailsView i cant see any data being displayed. Please help me

You're ViewModel has an ObservableCollection of items and you're binding directly to a property of one of the children. Instead you should use a ListBox and template your binding:
<ListBox x:Name="ContentPanel" ItemsSource="{Binding PeopleDetails}" Grid.Row="1" Margin="12,0,12,0">
<ListBox.ItemTemplate>
<DataTemplate>
<Image Height="250" HorizontalAlignment="Left" Margin="12,6,0,0" Name="image1" Stretch="Fill" Source="{Binding _Person_image_link}" VerticalAlignment="Top" Width="246" />
<ScrollViewer Grid.Row="1" Height="274" HorizontalAlignment="Left" Margin="12,42,0,0" Name="scrollViewer1" VerticalAlignment="Top" Width="420">
<TextBlock Height="264" Name="textBlock1" Text="{Binding _Person_info}" />
</ScrollViewer>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>