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Just out of curiosity... is the Category property not null when the initial binding occurs? Meaning you set the Category property the combobox is bound against to an instance of your class either at the declaration of the backing variable or in the datacontext constructor?
There is an annoying "feature" that if you try to bind to a property that exposes an object and that object is null when the binding occurs, then eventing doesn't work. For example, if you bind a combobox itemsource to a collection that is initially null, even if you set the property to a fully-populated collection later, the combobox will not pickup the change. There has to be an instance of the class exposing the PropertyChanged event at the time of the binding for it to work. Especially helpful in these cases is that there are no errors. Raising the property changed event just goes nowhere.
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I flattened the model due to some database design problems that I can't (not allowed to) fix. As such I am exposing the categoryId and categoryName property on the type object. I can use most of the same framework, the question is how do I cleanly update the categoryName when the Id is updated?
I could put a lookup into the PropertyChanged event of the categoryId, but it seems dirty to have to visit the database from the model object. Seems dirty, thoughts?
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Sorry for the delay getting back...
I understand your concerns. You didn't say that you are using MVVM but since you are talking about a model class I'm guessing you are, in fact, using it. If that is the case, you should put all of your database code in the model. The idea of the model is to hide the details of the backing data store so you could switch it out if you needed. So it may feel dirty but that is exactly what you are supposed to be doing.
I have fallen into a pattern where I usually create two classes for data. I'll call them DataObject and DataModel (really xxxxObject and xxxxModel as appropriate). DataObject represents the actual data and is typically nothing more than a class with a bunch of public properties. I usually inherit INotifyPropertyChanged and INotifyDataError on that class so that it can alert to value changes and it can alert to bad values.
The second class, DataModel, is where I put the data access functions. This class is data source specific and usually implements an interface I have specified with the functions I'll need. In your case, this class might expose a function like:
public CategoryBase GetCategoryById(int Id)
which would obviously return a category based on an Id. In your ViewModel you would have a property which would take a category ID and in the setter you would call the GetCategoryById then use the results to set the category and Id on the property exposing that data object. As long as the underlying DataObject implements INPC and you have bound to a non-null category object at startup, then the category and Id should follow along with changes in the Id sourced from the combobox.
The grid complicates things a bit because you have a collection of the data objects but that is pretty easy to work around. If you are uncomfortable wiring it up from the property setter for the Id property, remember that Combobox exposes a selection changed event. You could bind a command to that and use that as a jump point to call the DB fetch method and set the category data object.
Ultimately though... I suggest you take MVVM as a suggestion and not a set of hard and fast rules. Like a lot of stuff in software development, there is always some scenario that doesn't fit the rules so we end up breaking them to make it work. If you figure out a system that works, then consider it a success. Just document the code so the next guy can see why you did what you did and why you broke the rule. 
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Yes, it is MVVM, I should have mentioned as much. My project is laid out as described, Business Object, Data Access Layer. The business object is responsible for retrieving the data from the database and transforming it into classes suitable for the View and ViewModel. The VM has not interaction with the DAL, just the Business Layer.
That is where the dirtiness comes in, it comes from the fact that the model class would have to interact with the database where currently it is the business object that handles that. It isn't the end of the world, though. If I have the model call the business layer to retrieve the name, I won't feel so bad. Thank you for all your help.
There is no strict adherence to the MVVM pattern here, more of a loose guideline, I just want to make sure that if we change our DAL we have one place to look (BizLayer) to figure out what needs to be changed.
Pipedream, I am sure.
Cheers, --EA
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I facilitated the loading of my window height and width of my Border I named BorderSplash.
animation works fine but the problem is that it does not stop what I want to avoid.
<Storyboard x:Key="AnimGrossirImage" >
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="Width" Storyboard.TargetName="BorderSplash">
<EasingDoubleKeyFrame KeyTime="0" Value="5"></EasingDoubleKeyFrame>
<EasingDoubleKeyFrame KeyTime="0:0:3" Value="300" ></EasingDoubleKeyFrame>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="Height" Storyboard.TargetName="BorderSplash" AutoReverse="False">
<EasingDoubleKeyFrame KeyTime="0" Value="5" ></EasingDoubleKeyFrame>
<EasingDoubleKeyFrame KeyTime="0:0:0.7" Value="300" ></EasingDoubleKeyFrame>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
Thank you in advance for your help!
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Member 10016140 wrote: but the problem is that it does not stop what I want to avoid.
When you want to stop the animation ?
are there fixed triggers that you can use?
you can use BeginStoryBoard and StopStoryBoard with Triggers.
Read this[^] and this.[^]
don't worry and don't get frustrated. everything will eventually sort out and then we will regret being frustrated. the only thing that matters is conscious efforts to make things right. - Rahul Rajat Singh
Just that something can be done, doesn't mean it should be done. Respect developers and their efforts! - Jyothikarthik_N
modified 21-Jan-14 4:56am.
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I have a listbox with checkbobxes in it:
<ListBox Grid.Row="1"
ItemsSource="{Binding EmployeesInDept}"
Style="{StaticResource ListBoxStyle}"
Margin="5">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding IsChecked}"
IsEnabled="{Binding DataContext.AllowChangeEmpIsChecked, RelativeSource={RelativeSource AncestorType=TrainingTemplateEditorView}}"
Margin="0,0,3,0"/>
<TextBlock Text="{Binding EmployeeName}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
The list is bound to a collection of EmployeeSummaryEntity, which has an IsChecked property on it.
I have a property on my viewmodel called AllowChangeEmpIsChecked. I want to enabled/disable ALL the checkboxes in the list when other conditions in the VM are true but it's not working. Anyone see what I'm doing wrong?
Thanks
If it's not broken, fix it until it is
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<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding IsChecked}"
IsEnabled="{Binding DataContext.AllowChangeEmpIsChecked, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}"
Margin="0,0,3,0"/>
<TextBlock Text="{Binding EmployeeName}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
I think the issue is with the RelativeSource property of the binding.
"As beings of finite lifespan, our contributions to the sum of human knowledge is one of the greatest endeavors we can undertake and one of the defining characteristics of humanity itself"
modified 23-Jan-14 1:14am.
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A couple things:
1. Are you sure that it is not disabled? Stupid disabled checkboxes still look enabled often times unless you specifically change the style of a disabled checkbox.
2. Are you sure that your binding path is resolving correctly? Make sure you are not getting a "blah not found on object blah" error in output.
You can try handling this with a style trigger as well.
<Style x:TargetType="CheckBox">
<Style.Triggers>
<DataTrigger Binding="Your correct path here">
<Setter Property="IsEnabled" Value="False" />
</DataTrigger>
</Style.Triggers>
</Style>
Something like that anyways.
Cheers, --EA
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Hi everybody,
I just installed vs2013 and I carried a WPF project, previous developed with VS2010, under this environment. Happens to me a very strange thing that obviously does not happen with 2010 .... I have my own custom control that defines a runtime URI to a dictionary ... the strangeness lies in the fact that in the code of xaml page when i define the use of my control, i've got the error reported in subject... but the strangest thing is that if i start the dubug, everything works fine and the style is correctly applied .... someone has an idea?
the code look like that :
the custom control
using System;
using System.Windows.Controls;
using System.Windows;
using System.ComponentModel;
using System.Windows.Data;
namespace myListView
{
public class myListView : ListView
{
protected override void OnInitialized(EventArgs e)
{
Uri uri = new Uri("Skins\\myDictionary.xaml", UriKind.Relative);
dictionary = Application.LoadComponent(uri) as ResourceDictionary;
base.OnInitialized(e);
}
}
}
the xaml page
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:xlw="clr-namespace:myListView;assembly=myListView"
Title="MainWindow" Height="350" Width="525">
<Grid>
<xlw:myListView>
<!-- the editor tell me that can t find the Skins/myDictionary.xaml -->
</xlw:myListView>
</Grid>
</Window>
P.S. The custom control is an external dll included in Reference...it's one of my several generic object that i use in several solution
modified 10-Jan-14 6:04am.
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I find that the xaml design interface regularly fails when dealing with custom controls and particularly complex layouts, this is not new to 2013.
Never underestimate the power of human stupidity
RAH
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thank you for your reply...but have you ever find a workaround ? i can't believe that i can't migrate my project to the new platform....
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You mean a new version!
I believe is is probably a bug in VS where is the xaml is too complex and it fails to render it. As irritating as it is I have never bothered to try and resolve the issue as it rarely happens and the resolution would probably take too much time anyway.
I now try and keep a views complexity down 
Never underestimate the power of human stupidity
RAH
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i don't think it's a complexity problem....i add a simple example in my first post where i've got the problem...
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As Mycroft has stated it's a XAML designer issue. The same bug is in VS2012. 
"As beings of finite lifespan, our contributions to the sum of human knowledge is one of the greatest endeavors we can undertake and one of the defining characteristics of humanity itself"
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Unbelivable ! I'll try to send the bug report to Microsoft tech support...
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I am trying to create a UI where I can move objects around. At the same time I need to be able to interact with the objects.
I am following this example[^].
I have looked at this many times before, and it get confusing, but I do understand some of it.
So far I have this:
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="..\AppResources.xaml"/>
</ResourceDictionary.MergedDictionaries>
<!-- MoveThumb Template -->
<ControlTemplate x:Key="MoveThumbTemplate" TargetType="{x:Type classes:MoveThumb}">
<Rectangle Fill="Transparent"/>
</ControlTemplate>
<!-- ResizeDecorator Template -->
<ControlTemplate x:Key="ResizeDecoratorTemplate" TargetType="{x:Type Control}">
<Grid>
<classes:ResizeThumb Height="3" Cursor="SizeNS" Margin="0 -4 0 0" VerticalAlignment="Top" HorizontalAlignment="Stretch"/>
<classes:ResizeThumb Width="3" Cursor="SizeWE" Margin="-4 0 0 0" VerticalAlignment="Stretch" HorizontalAlignment="Left"/>
<classes:ResizeThumb Width="3" Cursor="SizeWE" Margin="0 0 -4 0" VerticalAlignment="Stretch" HorizontalAlignment="Right"/>
<classes:ResizeThumb Height="3" Cursor="SizeNS" Margin="0 0 0 -4" VerticalAlignment="Bottom" HorizontalAlignment="Stretch"/>
<classes:ResizeThumb Width="7" Height="7" Cursor="SizeNWSE" Margin="-6 -6 0 0" VerticalAlignment="Top" HorizontalAlignment="Left"/>
<classes:ResizeThumb Width="7" Height="7" Cursor="SizeNESW" Margin="0 -6 -6 0" VerticalAlignment="Top" HorizontalAlignment="Right"/>
<classes:ResizeThumb Width="7" Height="7" Cursor="SizeNESW" Margin="-6 0 0 -6" VerticalAlignment="Bottom" HorizontalAlignment="Left"/>
<classes:ResizeThumb Width="7" Height="7" Cursor="SizeNWSE" Margin="0 0 -6 -6" VerticalAlignment="Bottom" HorizontalAlignment="Right"/>
</Grid>
</ControlTemplate>
<!-- Designer Item Template-->
<ControlTemplate x:Key="DesignerItemTemplate" TargetType="ContentControl">
<Grid DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}">
<classes:MoveThumb Template="{StaticResource MoveThumbTemplate}" Cursor="SizeAll"/>
<Control Template="{StaticResource ResizeDecoratorTemplate}"/>
<ContentPresenter Content="{TemplateBinding ContentControl.Content}"/>
</Grid>
</ControlTemplate>
</ResourceDictionary>
</Window.Resources>
<Canvas Grid.Row="2"
Grid.Column="0"
Background="Transparent">
<ContentControl Name="DesignerItem"
Width="100"
Height="100"
Canvas.Top="100"
Canvas.Left="100"
Template="{StaticResource DesignerItemTemplate}">
<TextBox Grid.Row="1"
IsHitTestVisible="False"
Text="This is some text"
Height="Auto">
</TextBox>
</ContentControl>
</Canvas>
When I run it, I see Resize handles on all 4 corners of the textbox, and I can click & drag. The problem is that I cannot edit the text in the text box because the IsHitTestVisible property on the textbox Is False.
Set IsHitTestVisible = true and you can no longer drag & resize.
What I'd like is to be able to both drag/drop AND edit.
Can anyone help?
Thanks
If it's not broken, fix it until it is
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You are trying to implement something like this; WPF Surface Panel[^]
"As beings of finite lifespan, our contributions to the sum of human knowledge is one of the greatest endeavors we can undertake and one of the defining characteristics of humanity itself"
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wow i am fighting with this for 2 days now !
i am displaying the result of this linq query in a wpf datagrid
var v = from p in _context.EXAMENS_VALEURs
join b in _context.EXAMENS_TYPES_VALEURs on p.EXV_ID_VALEUR_TYPE equals b.ID_EXAMEN_TYPE_VALEUR
join c in _context.EXAMENS_TYPES_GROUPEs on b.EXTV_ID_GROUPE equals c.ID_EXAMEN_TYPE_GROUPE
select new ValeursResult()
{
ID = p.ID_EXAMEN_VALEUR,
Designation = b.EXTV_DESIGNATION,
Groupe = c.EXTG_DESIGNATION,
Valeur = p.EXV_VALEUR
};
((CollectionViewSource)this.FindResource("ExamensView")).Source = v.ToList();
the ValeursResult type is declared like this
public class ValeursResult
{
public int ID { get; set; }
public string Groupe { get; set; }
public string Designation { get; set; }
public string Valeur { get; set; }
}
the datagris id bound to the collectionviewdource with this
<DataGrid x:Name="grd2" AutoGenerateColumns="True"
ItemsSource="{Binding Source={StaticResource ExamensView}}" />
now i can view the result in my datagrid, i can change the values in the cells ,
but the update is not done on the server with
_context.Savechanges()
i have also tried this line of code just before calling savechanges
((ListCollectionView)((CollectionViewSource)this.FindResource("ExamensView")).View).CommitEdit();
but again the databse table is never updated
btw i am using telerik orm with a firebid database
thanks for your help
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I want to learn WPF.
How Can i start learning.
Give me guidance or tutorial about that.
so, i can learn it step by step..
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I have this HierarchicalDataTemplate. It has a checkbox bound to a property called IsChecked on the DatabaseEntity model:
<HierarchicalDataTemplate DataType="{x:Type entities:DatabaseEntity}"
ItemsSource="{Binding Path=Items}">
<Grid Margin="2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<CheckBox IsChecked="{Binding IsChecked}"
Grid.Column="0"/>
<Image Grid.Column="1"
Height="16"
Width="16"
Margin="0,0,3,0"
Source="/Osprey.UI.WPF;component/Media/database_64.png" />
<TextBlock Grid.Column="2">
<Hyperlink NavigateUri="{Binding Text}"
Foreground="#0C2DAA"
Style="{StaticResource linkStyle}"
CommandParameter="{Binding}"
Command="{Binding Path=DataContext.SelectedNodeCommand,
RelativeSource={RelativeSource FindAncestor,
AncestorType={ x:Type views:MainWindowView}}}">
<InlineUIContainer>
<TextBlock Text="{Binding Text}"
FontSize="12"/>
</InlineUIContainer>
</Hyperlink>
</TextBlock>
</Grid>
</HierarchicalDataTemplate>
When I check the checkbox, I'd like the VM to know about it was well as the model. How can I do this?
Thanks
If it's not broken, fix it until it is
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I assume your model implements INotifyPropertyChanged Interface. In your VM, you can subscribe to the model's property changed event, and then check if the IsChecked property is the one being changed. If the instance of the model is inside a collection (I assume it is as this is a hierarchicaltemplate), you will need to subscribe to the collection's collection changed event, then inside that method, you subscribe to each instance's property changed event.
Something like this
Items.CollectionChanged += ItemsChanged;
private void ItemsCHanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
if(e.NewItems != null)
{
foreach(Item item in e.NewItems)
{
item.PropertyChanged += ItemChanged;
}
}
if (e.OldItems != null)
{
foreach (Item item in e.OldItems)
{
item.PropertyChanged -= ItemChanged;
}
}
}
private void ItemChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
if(e.PropertyName == "IsChecked")
{
}
}
When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman
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Why not raise an event from the model, then subscribe to the event for each item in the list?
If it's not broken, fix it until it is
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