I am trying to reproduce the BingMaps sample of the Windows Phone 7 trainingkit:
http://msdn.microsoft.com/en-us/wp7trainingcourse_usingbingmapslab_topic2.aspx#_Toc271039352
but instead of wiring everything in codebehind i'd like to use a viewmodel.
Everything works fine except binding to the Mode property (aerial or road) causes a XamlParseException.
Is there a problem because it isn't a simple property?
This is the original Xaml:
<my:Map Name="Map"
CredentialsProvider="{Binding CredentialsProvider}">
<my:Map.Mode>
<my:AerialMode ShouldDisplayLabels="True" />
</my:Map.Mode>
</my:Map>
The Map.Mode can be changed from codebehind.
Instead I am trying the following:
<my:Map x:Name="Map"
CredentialsProvider="{Binding CredentialsProvider}"
ZoomLevel="{Binding Zoom, Mode=TwoWay}"
Center="{Binding Center, Mode=TwoWay}"
Mode="{Binding MapMode}" />
and the important part of the viewmodel:
private MapMode _mapMode = new AerialMode(true);
public MapMode MapMode
{
get { return _mapMode; }
set
{
_mapMode = value;
RaisePropertyChanged("MapMode");
}
}
private void ChangeMapMode()
{
if (MapMode is AerialMode)
{
MapMode = new RoadMode();
}
else
{
MapMode = new AerialMode(true);
}
}
Thanks for your help!
Solved.
"Mode" isn't a dependency property. So it cannot be bound.
My workaround:
added dependency property to view (=Page)
bound dependency property to property in viewmodel (via code in the constructor)
Set Mode of Map control in the propertyChanged callback handler
//Constructor
public MainPage()
{
InitializeComponent();
DataContext = new MainViewModel();
Binding b = new Binding("MapMode");
this.SetBinding(MapModeProperty, b);
}
//DependencyProperty. No need for corresponding CLR-property.
public static readonly DependencyProperty MapModeProperty =
DependencyProperty.Register("MapMode", typeof(MapMode), typeof(MainPage),
new PropertyMetadata(OnMapModeChanged));
//Callback
private static void OnMapModeChanged(DependencyObject element,
DependencyPropertyChangedEventArgs e)
{
((MainPage)element).Map.Mode = e.NewValue as MapMode;
}
Hope this one will help others!
I suspect you'll need to use a converter with your binding.
Related
I have a multiselect Combobox usercontrol and a dependency property 'SelectedItems'.
I m trying to use the usercontrol and bind the 'SelectedItems' to another property called 'SelectedResultItems' in my ViewModel. But I dont get any values to SelectedResultItems. Please help
Here is what i tried.
My main xaml:
<DataTemplate x:Key="TypeATemplate">
<control:MultiSelectComboBox Width="315" ItemsSource="{Binding
ResultvalueList,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
SelectedItems="{Binding
SelectedResultItems,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>
</DataTemplate>
My Combobox usercontrol code behind:
public static readonly DependencyProperty SelectedItemsProperty =
DependencyProperty.Register("SelectedItems",
typeof(ObservableCollection<string>), typeof(MultiSelectComboBox), new
FrameworkPropertyMetadata(null,new
PropertyChangedCallback(MultiSelectComboBox.OnSelectedItemsChanged)));
public ObservableCollection<string> SelectedItems
{
get { return
(ObservableCollection<string>)GetValue(SelectedItemsProperty); }
set
{
SetValue(SelectedItemsProperty, value);
}
}
I am setting the 'SelectedItems' on click of the checkbox.
My mainviewmodel:
public ObservableCollection<string> SelectedResultItems
{
get => _selectedResultItems;
set
{
_selectedResultItems = value;
NotifyPropertyChanged(nameof(SelectedResultItems));
}
}
If this is the same as for ListView(never used MultiSelectCombobox), you cannot bind to SelectedItems because it is a read-only property.
What I did to solve that is add the event SelectionChanged to ListView(or MultiSelectCombobox for you).
Then event would be :
private void YourComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
contexte.ResultItems = YourComboBox.SelectedItems.Cast<YourItem>().ToList();
}
Maybe there is a different way to do it, but until now that's the easiest way I found.
I have created a custom control CustomTextBox inherited from TextBox class. I have created a dependency property named CustomTextProperty.
I have binded this DP with my Viewmodel property.
While Registering the DP i have given the property change callback but it is only get called one time when my control gets the binded data initially when my xaml loads.
When i try to set my control from view the binded VM property setter does not gets called and also the propertychangecallback not gets fired.
Please help!!
Code snipet below:
My Custom control
class CustomTextBox : TextBox
{
public static readonly DependencyProperty CustomTextProperty = DependencyProperty.Register("CustomText",
typeof(string), typeof(CustomTextBox),
new FrameworkPropertyMetadata("CustomTextBox",
FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
new PropertyChangedCallback(OnCustomPropertyChange)));
public string CustomText
{
get { return (string)GetValue(CustomTextProperty); }
set { SetValue(CustomTextProperty, value); }
}
private static void OnCustomPropertyChange(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// This is Demo Application.
// Code to be done Later...
}
}
My View Model:
public class ViewModel : INotifyPropertyChanged
{
private string textForTextBox;
public string TextForCustomTextBox
{
get
{
return this.textForTextBox;
}
set
{
this.textForTextBox = value;
this.OnPropertyChange("TextForCustomTextBox");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChange(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
My Xaml Code with Binding:
<custom:CustomTextBox x:Name="CustomTextBox"
CustomText="{Binding TextForCustomTextBox, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
Grid.Row="1" HorizontalAlignment="Center" Width="200" Height="50" />
My Code Behind to set DataContext:
// My View Constructor
public View1()
{
InitializeComponent();
this.DataContext = new ViewModel();
}
You said that you declared a CustomText DependencyProperty and data bound it to your view model TextForCustomTextBox property and that much is correct. However, when you said that you tried to set your property from the view, you were mistaken.
What you were actually doing was setting the CustomTextBox .Text property from the view and that wasn't connected to your CustomTextBox.CustomText property. You can connect them like this, although I'm not quite sure what the point of that would be:
<Views:CustomTextBox x:Name="CustomTextBox" Text="{Binding CustomText, RelativeSource={
RelativeSource Self}, UpdateSourceTrigger=PropertyChanged}" CustomText="{Binding
TextForCustomTextBox, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
Grid.Row="1" HorizontalAlignment="Center" Width="200" Height="50" />
Try setting your DataContext BEFORE the actual initialization so it is available when the form/control objects are created. If it can't find before, is that what may be causing the failed bindings.
I have a custom UserControl that contains a grid ...I wish to set the ItemsSource property of that grid by xaml code of of a data template in a resource dictionary...
then I have used dependency property... this is my implementation...
public partial class MyControlGrid : UserControl
{
// Dependency Property
public static readonly DependencyProperty MyItemSourceProperty =
DependencyProperty.Register("MyItemSource", typeof(ICollectionView),
typeof(MyControlGrid), new FrameworkPropertyMetadata(null, OnMyItemSourcePropertyChanged));
IDictionary<string, string> _columns = new Dictionary<string, string>();
private static void OnMyItemSourcePropertyChanged(DependencyObject obj,
DependencyPropertyChangedEventArgs args)
{
// When the color changes, set the icon color PlayButton
MyControlGrid muc = (MyControlGrid)obj;
ICollectionView value = (ICollectionView)args.NewValue;
if (value != null)
{
muc.MyGridControl.ItemsSource = value;
}
}
public ICollectionView MyItemSource
{
get
{
return (ICollectionView)GetValue(MyItemSourceProperty);
}
set
{
SetValue(MyItemSourceProperty, value);
//OnTargetPowerChanged(this, new DependencyPropertyChangedEventArgs(TargetPowerProperty, value, value));
// Old value irrelevant.
}
}
public MyControlGrid()
{
InitializeComponent();
}
}
this is the user control xaml code
<UserControl x:Class="GUI.Design.Templates.MyControlGrid"
Name="MyListControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:WpfTkit="http://schemas.microsoft.com/wpf/2008/toolkit"
xmlns:Templates="clr-namespace:Emule.GUI.Design.Templates">
<StackPanel>
<WpfTkit:DataGrid ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Templates:MyControlGrid}}, Path=MyItemSource}"
x:Name="MyGridControl"
<StackPanel>
this is the binding path expression I use
<basic:MyControlGrid MyItemSource="{Binding MyDataContextVisibleCollection}"/>
this dont work and wpf output window dont show me any errors
note that, naturally, if I bind this directly in the user controls work fine
<WpfTkit:DataGrid ItemsSource="{Binding MyDataContextVisibleCollection}"
Waths I wrong?
thanks
p.s. sorry for my english
this
answer show me the way
use of PropertyChangedCallback work fine with my code:
public static readonly DependencyProperty MyItemSourceProperty =
DependencyProperty.Register("MyItemSource", typeof(IEnumerable),
typeof(MyControlGrid), new FrameworkPropertyMetadata(null,
new PropertyChangedCallback(MyControlGrid.OnItemsSourceChanged)));
alternatively I have to remove comment on OnTargetPowerChanged and fire the property changed event
set
{
SetValue(MyItemSourceProperty, value);
//OnTargetPowerChanged(this, new DependencyPropertyChangedEventArgs(TargetPowerProperty, value, value));
// Old value irrelevant.
}
correct with
public ICollectionView MyItemSource
{
get
{
return (ICollectionView)GetValue(MyItemSourceProperty);
}
set
{
SetValue(MyItemSourceProperty, value);
OnItemsSourceChanged(this, new DependencyPropertyChangedEventArgs(MyItemSourceProperty, value, value));
}
}
This cannot be this difficult. The TreeView in WPF doesn't allow you to set the SelectedItem, saying that the property is ReadOnly. I have the TreeView populating, even updating when it's databound collection changes.
I just need to know what item is selected. I am using MVVM, so there is no codebehind or variable to reference the treeview by. This is the only solution I have found, but it is an obvious hack, it creates another element in XAML that uses ElementName binding to set itself to the treeviews selected item, which you must then bind your Viewmodel too. Several other questions are asked about this, but no other working solutions are given.
I have seen this question, but using the answer given gives me compile errors, for some reason I cannot add a reference to the blend sdk System.Windows.Interactivity to my project. It says "unknown error system.windows has not been preloaded" and I haven't yet figured out how to get past that.
For Bonus Points: why the hell did Microsoft make this element's SelectedItem property ReadOnly?
You should not really need to deal with the SelectedItem property directly, bind IsSelected to a property on your viewmodel and keep track of the selected item there.
A sketch:
<TreeView ItemsSource="{Binding TreeData}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsSelected" Value="{Binding IsSelected}" />
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
public class TViewModel : INotifyPropertyChanged
{
private static object _selectedItem = null;
// This is public get-only here but you could implement a public setter which
// also selects the item.
// Also this should be moved to an instance property on a VM for the whole tree,
// otherwise there will be conflicts for more than one tree.
public static object SelectedItem
{
get { return _selectedItem; }
private set
{
if (_selectedItem != value)
{
_selectedItem = value;
OnSelectedItemChanged();
}
}
}
static virtual void OnSelectedItemChanged()
{
// Raise event / do other things
}
private bool _isSelected;
public bool IsSelected
{
get { return _isSelected; }
set
{
if (_isSelected != value)
{
_isSelected = value;
OnPropertyChanged("IsSelected");
if (_isSelected)
{
SelectedItem = this;
}
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
var handler = this.PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
A very unusual but quite effective way to solve this in a MVVM-acceptable way is the following:
Create a visibility-collapsed ContentControl on the same View the TreeView is. Name it appropriately, and bind its Content to some SelectedSomething property in viewmodel. This ContentControl will "hold" the selected object and handle it's binding, OneWayToSource;
Listen to the SelectedItemChanged in TreeView, and add a handler in code-behind to set your ContentControl.Content to the newly selected item.
XAML:
<ContentControl x:Name="SelectedItemHelper" Content="{Binding SelectedObject, Mode=OneWayToSource}" Visibility="Collapsed"/>
<TreeView ItemsSource="{Binding SomeCollection}"
SelectedItemChanged="TreeView_SelectedItemChanged">
Code Behind:
private void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
SelectedItemHelper.Content = e.NewValue;
}
ViewModel:
public object SelectedObject // Class is not actually "object"
{
get { return _selected_object; }
set
{
_selected_object = value;
RaisePropertyChanged(() => SelectedObject);
Console.WriteLine(SelectedObject);
}
}
object _selected_object;
You can create an attached property that is bindable and has a getter and setter:
public class TreeViewHelper
{
private static Dictionary<DependencyObject, TreeViewSelectedItemBehavior> behaviors = new Dictionary<DependencyObject, TreeViewSelectedItemBehavior>();
public static object GetSelectedItem(DependencyObject obj)
{
return (object)obj.GetValue(SelectedItemProperty);
}
public static void SetSelectedItem(DependencyObject obj, object value)
{
obj.SetValue(SelectedItemProperty, value);
}
// Using a DependencyProperty as the backing store for SelectedItem. This enables animation, styling, binding, etc...
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.RegisterAttached("SelectedItem", typeof(object), typeof(TreeViewHelper), new UIPropertyMetadata(null, SelectedItemChanged));
private static void SelectedItemChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
if (!(obj is TreeView))
return;
if (!behaviors.ContainsKey(obj))
behaviors.Add(obj, new TreeViewSelectedItemBehavior(obj as TreeView));
TreeViewSelectedItemBehavior view = behaviors[obj];
view.ChangeSelectedItem(e.NewValue);
}
private class TreeViewSelectedItemBehavior
{
TreeView view;
public TreeViewSelectedItemBehavior(TreeView view)
{
this.view = view;
view.SelectedItemChanged += (sender, e) => SetSelectedItem(view, e.NewValue);
}
internal void ChangeSelectedItem(object p)
{
TreeViewItem item = (TreeViewItem)view.ItemContainerGenerator.ContainerFromItem(p);
item.IsSelected = true;
}
}
}
Add the namespace declaration containing that class to your XAML and bind as follows (local is how I named the namespace declaration):
<TreeView ItemsSource="{Binding Path=Root.Children}"
local:TreeViewHelper.SelectedItem="{Binding Path=SelectedItem, Mode=TwoWay}"/>
Now you can bind the selected item, and also set it in your view model to change it programmatically, should that requirement ever arise. This is, of course, assuming that you implement INotifyPropertyChanged on that particular property.
Use the OneWayToSource binding mode. This doesn't work. See edit.
Edit: Looks like this is a bug or "by design" behavior from Microsoft, according to this question; there are some workarounds posted, though. Do any of those work for your TreeView?
The Microsoft Connect issue: https://connect.microsoft.com/WPF/feedback/details/523865/read-only-dependency-properties-does-not-support-onewaytosource-bindings
Posted by Microsoft on 1/10/2010 at 2:46 PM
We cannot do this in WPF today, for the same reason we cannot support
bindings on properties that are not DependencyProperties. The runtime
per-instance state of a binding is held in a BindingExpression, which
we store in the EffectiveValueTable for the target DependencyObject.
When the target property is not a DP or the DP is read-only, there's
no place to store the BindingExpression.
It's possible we may some day choose to extend binding functionality
to these two scenarios. We get asked about them pretty frequently. In
other words, your request is already on our list of features to
consider in future releases.
Thanks for your feedback.
I decided to use a combination of code behind and viewmodel code. the xaml is like this:
<TreeView
Name="tvCountries"
ItemsSource="{Binding Path=Countries}"
ItemTemplate="{StaticResource ResourceKey=countryTemplate}"
SelectedValuePath="Name"
SelectedItemChanged="tvCountries_SelectedItemChanged">
Code behind
private void tvCountries_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
var vm = this.FindResource("vm") as ViewModels.CoiEditorViewModel;
if (vm != null)
{
var treeItem = sender as TreeView;
vm.TreeItemSelected = treeItem.SelectedItem;
}
}
And in the viewmodel there is a TreeItemSelected object which you can then access in the viewmodel.
You can always create a DependencyProperty that uses ICommand and listen to the SelectedItemChanged event on the TreeView. This can be a bit easier than binding IsSelected, but I imagine you will wind up binding IsSelected anyway for other reasons. If you just want to bind on IsSelected you can always have your item send a message whenever IsSelected changes. Then you can listen to those messages anyplace in your program.
I am working on an application where Repository objects are displayed via a DataTemplate that contains a modified version of a TextBox, which supports binding to the SelectionStart, SelectionLength, and VerticalOffset.
The DataTemplate looks like this:
<DataTemplate DataType="{x:Type m:Repository}">
<controls:ModdedTextBox
x:Name="textBox" Text="{Binding Text, UpdateSourceTrigger=PropertyChanged}"
BindableSelectionStart="{Binding SelectionStart, UpdateSourceTrigger=PropertyChanged}"
BindableSelectionLength="{Binding SelectionLength, UpdateSourceTrigger=PropertyChanged}"
BindableVerticalOffset="{Binding VerticalOffset, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</DataTemplate>
The problem is that when I change the Repositorythat is currently being displayed; the SelectionStart, SelectionLength, and VerticalOffset all seem to be getting set to 0, even when those properties of the Repository object are not 0.
I think that this is happening in the instant before the text is displayed when the SelectionStart, SelectionLength, and VerticalOffset can not be more than 0. This does not only set the actual properties of the TextBox to zero, but also updates the bindings and sets the properties of the Repository object to zero.
Is there any way that I can prevent this from happening?
--Edit--
I don't know if posting dl links to projects is a no-no or not on SO, but here is a link to a project I created to demonstrate the problem I am having: http://dl.dropbox.com/u/1520079/RepositoryProblemDemo.zip
When you run the demo-app the selection you can click the "Switch Repository" button to change the repository that is displayed in the textbox. If you look to the right of the textbox the current repository's properties all get set to zero when you switch to the other one.
A difference between this demo and my actual app is that in my app repositories will be switched via hotkeys, not a button.
The problem is due to the fact that the bindings are evaluated in serial, and when the Text property is changed it causes all selection information to be removed (you can see this by putting breakpoints on your ModdedTextBox event handlers). As the BindableSelection... bindings are still active at that point, it causes the selection information to be reset.
Depending on the exact behaviour you want there is probably a way to work around this, but you would need to know a little more detail...
Edit in response to comments:
This solution isn't exactly answering your original question, and it probably isn't great practice, but it does at least work...
Try altering your ModdedTextBox so that instead of exposing bindable properties for the selection information, expose a single DP of type Repository and bind to that:
<local:ModdedTextBox
x:Name="textBox"
Repository="{Binding CurrentRepository}"
TextWrapping="Wrap"
/>
Then handle the changed event on your DP to set the text box properties:
public static DependencyProperty RepositoryProperty =
DependencyProperty.Register("Repository",
typeof(Repository), typeof(ModdedTextBox), new PropertyMetadata(null, OnRepositoryChanged));
public Repository Repository
{
get { return (Repository)base.GetValue(RepositoryProperty); }
set { base.SetValue(RepositoryProperty, value); }
}
private static void OnRepositoryChanged(DependencyObject senderObject, DependencyPropertyChangedEventArgs e)
{
var sender = (ModdedTextBox)senderObject;
var oldRepository = e.OldValue as Repository;
var newRepository = e.NewValue as Repository;
if (oldRepository != null)
{
oldRepository.Text = sender.Text;
oldRepository.SelectionStart = sender.SelectionStart;
//etc
}
if (newRepository != null)
{
sender.Text = newRepository.Text;
sender.SelectionStart = newRepository.SelectionStart;
//etc
}
}
This is essentially removing the serial nature of the binding evaluation.
Note: You could also achieve the same using attached properties, which would be better than subclassing TextBox, but this is closer to your original attempts so I figure its easier to explain!
Here is a re-write of the other solution. This one takes into account the text property not being bound before the other properties.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
namespace WpfApplication1
{
public class SelectionBindingTextBox : TextBox
{
public static readonly DependencyProperty BindableSelectionStartProperty =
DependencyProperty.Register(
"BindableSelectionStart",
typeof(int),
typeof(SelectionBindingTextBox),
new PropertyMetadata(OnBindableSelectionStartChanged));
public static readonly DependencyProperty BindableSelectionLengthProperty =
DependencyProperty.Register(
"BindableSelectionLength",
typeof(int),
typeof(SelectionBindingTextBox),
new PropertyMetadata(OnBindableSelectionLengthChanged));
private bool isBindingComplete = false;
public SelectionBindingTextBox()
: base()
{
this.SelectionChanged += this.OnSelectionChanged;
this.TextChanged += this.OnTextChanged;
}
public int BindableSelectionStart
{
get
{
return (int)this.GetValue(BindableSelectionStartProperty);
}
set
{
this.SetValue(BindableSelectionStartProperty, value);
}
}
public int BindableSelectionLength
{
get
{
return (int)this.GetValue(BindableSelectionLengthProperty);
}
set
{
this.SetValue(BindableSelectionLengthProperty, value);
}
}
private static void OnBindableSelectionStartChanged(DependencyObject dependencyObject,
DependencyPropertyChangedEventArgs args)
{
var textBox = dependencyObject as SelectionBindingTextBox;
if (textBox.isBindingComplete)
{
textBox.SetupSelection();
}
}
private static void OnBindableSelectionLengthChanged(DependencyObject dependencyObject,
DependencyPropertyChangedEventArgs args)
{
var textBox = dependencyObject as SelectionBindingTextBox;
if (textBox.isBindingComplete)
{
textBox.SetupSelection();
}
}
private void OnSelectionChanged(object sender, RoutedEventArgs e)
{
if (isBindingComplete)
{
this.BindableSelectionStart = this.SelectionStart;
this.BindableSelectionLength = this.SelectionLength;
}
}
private void OnTextChanged(object sender, RoutedEventArgs e)
{
if (!isBindingComplete)
{
SetupSelection();
}
isBindingComplete = true;
}
private void SetupSelection()
{
// this.Focus();
this.SelectionLength = this.BindableSelectionLength;
this.SelectionStart = this.BindableSelectionStart;
}
}
}
Well update of binding depends on the order in which WPF or Silverlight Engine will evaluate, looks like your SelectionStart and SelectionEnd bindings are updated before Text, so when Text gets changed, SelectionStart and SelectionEnd are both changed back to zero.
The only way is to hook for TextChanged event and refresh the bindings of SelectionStart and SelectionEnd or in WPF you can extend textbox as follow
public class MyTextBox : TextBox{
protected override OnTextChanged(TextChangedEventArgs e){
BindingExpression be = this.GetBindingExpression(SelectionStartProperty);
if(be!=null){
be.UpdateTarget();
}
be = this.GetBindingExpression(SelectionEndProperty);
if(be!=null){
be.UpdateTarget();
}
be = this.GetBindingExpression(VerticalOffsetProperty);
if(be!=null){
be.UpdateTarget();
}
}
}
Well here there is a trick, you still have to change above logic to fit in your logic because everytime text updates this will update binding, so you have to find out when to refresh these bindings. Because this will consistantly fail to change your textbox's value in runtime as text will modify and selection will goto previous selection only.