There is a UserControl which contains the bindings like below.
<TextBox Margin="5" Padding="0" IsReadOnly="True" Background="Transparent" BorderThickness="0" TextWrapping="Wrap" IsTabStop="False" FontSize="{DynamicResource TitleFontSize}" Text="{Binding ErrorTitle, Mode=OneWay}" />
it is bound by stack panel with name of GenericErrorControl and binding is as
<Visibility="{Binding IsShown, Mode=OneWay, Converter={StaticResource BoolToVis}, FallbackValue=Collapsed}">
Above control is added to one of view as below.
<views:GenericErrorControl Grid.Row="8" DataContext="{Binding GenericErrorControl, Mode=OneWay}" VerticalAlignment="Top/>
The problem is that user control is not appearing in the window after. In my viewmodel creating object i'm setting the value of IsShown but its not appearing. Kindly help and let me know if any other details needed.
It means that the binding is failing ie the fallback value is used from above code.
Things to do :
Ensure that your ViewModel inherits from the base class BindableBase ie it somehow implements the INotifyPropertyChanged interface and on property change, the PropertyChanged event is fired.
ie You have something similar to this in your view model.
private bool _IsShown;
public bool IsShown
{
get { return _IsShown; }
set { SetProperty(ref _IsShown, value); }
}
Double check your converter or post code here.
Related
I'm trying to create a new window (child of MainWindow) that will display different numbers of rows with data each time. I used the following template that I copied from a wpf template tutorial. I've checked that the data are right and I can project them right with a MessageBox.Show window but I can't make them appear as bound properties. Here is the xaml...
<ListView x:Name="listUnits" x:FieldModifier="public" HorizontalAlignment="Left" Height="Auto" Margin="5,5,5,5" VerticalAlignment="Top" Width="Auto">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Id:"/>
<TextBlock Text="{Binding pu_Id}" Width="Auto"/>
<TextBlock Text=" "/>
<TextBlock Text="{Binding pu_unitName}" Width="Auto"/>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
So although pu_unitName contains the data, they're are displayed in the new window.
The binding is done in the constructor:
public partial class ChooseUnit : Window
{
public ChooseUnit(List<XML_Handler.PrUnits> thisList)
{
InitializeComponent();
listUnits.ItemsSource = thisList;
}
}
The PrUnits is a class which contains variables including pu_id and pu_unitName. So what's wrong with this code?
Since you can only bind to public properties, you need to make sure that pu_Id and pu_UnitName are properties (and not fields) of the PrUnits class. Then your bindings will work.
Also note that this is not a binding:
listUnits.ItemsSource = thisList;
In general, you would set the DataContext of the parent window to an instance of a view model class and bind the ItemsSource property of the ListView to a property that returns the List<XML_Handler.PrUnits>:
<ListView x:Name="listUnits" ItemsSource="{Binding Units}">
...
In your .cs:
public partial class ChooseUnit : Window
{
public ChooseUnit(List<XML_Handler.PrUnits> thisList)
{
InitializeComponent();
this.DataContext = thisList;
}
}
What this does it assigns the data context of your window to the list of itemsa you are trying to pass. At this point every element in that window will have access to the passed in list.
And then in your XAML do this:
<ListView x:Name="listUnits" ItemsSource="{Binding .}" x:FieldModifier="public" HorizontalAlignment="Left" Height="Auto" Margin="5,5,5,5" VerticalAlignment="Top" Width="Auto">
This allows us to use binding as the entire window has access to the list. Hence ItemsSource="{Binding .}".
EDIT
Reading more into your question and thanks to Ash your class needs to expose Properties with INotifyPropertyChanged interface implemented.
This interface is expected by the WPF framework so it can subscribe to the changed events and update the UI.
I want to set a different content Template inside a button, to act like a Toggle Button, depending on the state of my ViewModel. I have simplified the code quite a bit, but in each Data Template the button's content draws different Path Geometries, together with a textblock.
ContentSelector class:
public class ContentSelector : DataTemplateSelector {
public DataTemplate TrueTemplate { get; set; }
public DataTemplate FalseTemplate { get; set; }
public override DataTemplate SelectTemplate(object item, DependencyObject container) {
if ((bool)item)
return TrueTemplate;
return FalseTemplate;
}
}
Edit: Added properties to the button to set its content, where 'State' isa boolean value in my ViewModel, and the converter is just returning 'T' or 'F', based on the State of my ViewModel
XAML:
<DataTemplate x:Key="HeaderTemplate">
<ContentPresenter>
<ContentPresenter.Content>
<DockPanel LastChildFill="False">
<Button Content="{Binding State, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ButtonContentConverter}}" Command="{Binding ToggleCommand}">>
<Button.ContentTemplateSelector>
<ContentSelector>
<local:ContentSelector.TrueTemplate>
<DataTemplate>
<TextBlock Text="T" ... />
</DataTemplate>
</local:ContentSelector.TrueTemplate>
<local:ContentSelector.FalseTemplate>
<DataTemplate>
<TextBlock Text="F" ... />
</DataTemplate>
</local:ContentSelector.FalseTemplate>
</ContentSelector>
</Button.ContentTemplateSelector>
</Button>
</DockPanel>
</ContentPresenter.Content>
</ContentPresenter>
</DataTemplate>
I cannot seem to hit the breakpoint in my ContentSelector class. It does work in the designer, meaning the button's content changes to 'T' or 'F' if I change it to return the corresponding DataTemplate in the ContentSelector Class, but when I run the application it never hits the ContentSelector, and the content of the button is completely empty.
Any ideas as to why this would happen? I have tried setting the Content of the button to the State of my ViewModel, and changing that to a boolean value using a converter, thinking that the content of the button must be set to trigger the ContentSelector, but it didnt work.
I'm fairly new to XAML but enjoying learning it. The thing I'm really struggling with is binding a property to an element in a DataTemplate.
I have created a simple WPF example to, (hopefully,) explain my problem.
I this example I am trying to bind the Visibility property of a CheckBox in a DataTemplate to a Property in my viewmodel. (Using this scenario purely for learning/demo.)
I have a simple DataModel named Item, but is of little relevance in this example.
class Item : INotifyPropertyChanged
{
// Fields...
private bool _IsRequired;
private string _ItemName;
And a fairly simple View Model named ItemViewModel.
class ItemViewModel : INotifyPropertyChanged
{
private ObservableCollection<Item> _Items;
private bool _IsCheckBoxChecked;
private bool _IsCheckBoxVisible;
public ObservableCollection<Item> Items
{
get { return _Items; }
set { _Items = value; }
}
public bool IsCheckBoxChecked
{
get { return _IsCheckBoxChecked; }
set
{
if (_IsCheckBoxChecked == value)
return;
_IsCheckBoxChecked = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("IsCheckBoxChecked"));
PropertyChanged(this, new PropertyChangedEventArgs("IsCheckBoxVisible"));
}
}
}
public bool IsCheckBoxVisible
{
get { return !_IsCheckBoxChecked; }
set
{
if (_IsCheckBoxVisible == value)
return;
_IsCheckBoxVisible = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("IsCheckBoxVisible"));
}
(Constructors and INotifyPropertyChanged implementation omitted for brevity.)
Controls laid out in MainPage.xaml as follows.
<Window.Resources>
<local:VisibilityConverter x:Key="VisibilityConverter"/>
</Window.Resources>
<Window.DataContext>
<local:ItemViewModel/>
</Window.DataContext>
<Grid>
<StackPanel>
<CheckBox x:Name="checkBox" Content="Hide CheckBoxes" FontSize="14" IsChecked="{Binding IsCheckBoxChecked, Mode=TwoWay}" />
<ListView ItemsSource="{Binding Items}" HorizontalContentAlignment="Stretch" >
<ListView.ItemTemplate >
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding ItemName}"/>
<CheckBox Grid.Column="1" Visibility="{Binding IsCheckBoxVisible, Converter={StaticResource VisibilityConverter}}" >
<CheckBox.DataContext>
<local:ItemViewModel/>
</CheckBox.DataContext>
</CheckBox>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<StackPanel Orientation="Horizontal" Margin="4,4,0,0">
<TextBlock Text="IsCheckBoxVisible:"/>
<TextBlock Text="{Binding IsCheckBoxVisible}" Margin="4,0,0,0" FontWeight="Bold" />
</StackPanel >
<Button Content="Button" Visibility="{Binding IsCheckBoxVisible, Converter={StaticResource VisibilityConverter}}" Margin="4,4,4,4"/>
</StackPanel>
</Grid>
The 'Hide CheckBoxes' checkbox is bound to IsCheckBoxChecked and is used to update IsCheckBoxVisible. I've also added a couple of extra controls below the DataTemplate to prove, (to myself,) the everything works.)
I have also implemented Jeff Wilcox's value converter. (Thank you.) http://www.jeff.wilcox.name/2008/07/visibility-type-converter/
When I run the app, checking and unchecking the 'Hide Checkbox', controls outside the DataTemplate function as expected but, alas, the Checkbox inside the data template remains unchanged.
I have had success with:
IsVisible="{Binding IsChecked, Converter={StaticResource VisibilityConverter}, ElementName=checkBox}"
But I'm not just trying mimic another control but make decisions based on a value.
I would REALLY appreciate any help or advice you can offer.
Thank you.
When you are in a DataTemplate, your DataContext is the data templated object, in this case an Item. Thus, the DataContext of the CheckBox in the DataTemplate is an Item, not your ItemViewModel. You can see this by your <TextBlock Text="{Binding ItemName}"/>, which binds to a property on the Item class. The Binding to IsCheckBoxVisible is trying to find a property called IsCheckBoxVisible on Item.
There are a couple of ways around this, but by far the easiest is to do this:
On your Window (in the xaml), give it and x:Name. Eg:
<Window [...blah blah...]
x:Name="MyWindow">
Change your binding to look like this:
<CheckBox Grid.Column="1"
Visibility="{Binding DataContext.IsCheckBoxVisible, ElementName=MyWindow, Converter={StaticResource VisibilityConverter}}">
We're using the Window as the source for the Binding, then looking at its DataContext property (which should be your ItemViewModel, and then pulling off the IsCheckBoxVisible property.
Another option, if you want something fancier, is to use a proxy object to reference your DataContext. See this article on DataContextProxy.
I have button at first column in datagrid. I am using MVVM and try to bind Command to Command in ViewModel but when I click button in each row, it don't work (It don't call Command in ViewModel) but if I move that button out of datagrid it's working properly.
How can I fire event from button inside datagrid in MVVM?
Update 1:
XAML's code is:
<datagrid:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal"
VerticalAlignment="Center">
<Button x:Name="button" Content="View" Margin="5" DataContext="{StaticResource XDataContext}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<i:InvokeCommandAction Command="{Binding ViewOrganizationCommand}"
CommandParameter="{Binding ElementName=dtgOrganizations, Path=SelectedItem}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
</StackPanel>
</DataTemplate>
</datagrid:DataGridTemplateColumn.CellTemplate>
ViewModel's code is:
public ViewModelCommand ViewOrganizationCommand { get; set; }
Instead of using EventTrigger, why not simply bind to Button.Command directly, like so?
<Button
...other properties...
Command="{Binding ViewOrganizationsCommand}"
CommandParameter="{Binding}"/>
That will bind the command, and set the CommandParameter to the DataContext of the Button, which presumably is a good thing to bind the parameter to. If it's not, just bind CommandParameter to something else that helps you uniquely identify the specific row being clicked on.
This article brings the solution with DataContextProxy. Applying this solution makes possible to write a button code like Austin Lamb's answer.
The command binding using the Event Trigger looks fine (This is how i always do it),
But I suspect that your command is never assigned to (You are using Automatic Properties)
I usually do it like this:
private ViewModelCommand viewOrganizationCommand;
public ViewModelCommand ViewOrganizationCommand
{
get
{
if (viewOrganizationCommand == null)
viewOrganizationCommand = new ViewModelCommand(Action, CanDoIt);
return viewOrganizationCommand;
}
}
try setting you Button's DataContext to the StackPanel and set the Command and CommandParameter of the Button.
<datagrid:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal"
VerticalAlignment="Center" DataContext="{StaticResource XDataContext}">
<Button x:Name="button" Content="View" Margin="5" Command="{Binding ViewOrganizationCommand}" CommandParameter="{Binding ElementName=dtgOrganizations, Path=SelectedItem}" >
</Button>
</StackPanel>
</DataTemplate>
</datagrid:DataGridTemplateColumn.CellTemplate>
I solved this problem by use EventToCommand behavior in MVVMLight Toolkit
Each row of the DataGrid has it's DataContext set to that object. If the ItemSource for the grid is an ObservableCollection, each row's DataContext is the Organization object.
There are two ways to handle this.
Create a wrapping or extension ViewModel that exposes the command. Then the command should fire.Here is some psuedo code.
public class OrganizationExtensionViewModel
{
<summary>
/// Private currentOrginization property.
/// </summary>
private Organization currentOrginization;
public Organization CurrentOrganization
{
get
{
return this.currentOrginization;
}
set
{
if (this.currentOrginization != value)
{
this.currentOrginization = value;
this.RaisePropertyChanged("CurrentOrganization");
}
}
}
public ViewModelCommand ViewOrganizationCommand { get; set; }
public OrganizationExtensionViewModel(Organization o)
{
this.CurrentOrganization = o;
this.ViewOrganizationCommand = new ViewModelCommand(this.ViewOrgnaizationClicked);
}
}
Define the ViewModel in the xaml as a StaticResource and refer to it as the binding path.
...
In the grid
<Button x:Name="button" Content="View" Margin="5" Command="{Binding ViewOrganizationCommand, Source={StaticResource viewModel}}" />
Can anyone help with the following - been playing about with this but can't for the life of me get it to work.
I've got a view model which contains the following properties;
public ObservableCollection<Rule> Rules { get; set; }
public Rule SelectedRule { get; set; }
In my XAML I've got;
<ListBox x:Name="lbRules" ItemsSource="{Binding Path=Rules}"
SelectedItem="{Binding Path=SelectedRule, Mode=TwoWay}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Name:" />
<TextBox x:Name="ruleName">
<TextBox.Text>
<Binding Path="Name" UpdateSourceTrigger="PropertyChanged" />
</TextBox.Text>
</TextBox>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
Now the ItemsSource works fine and I get a list of Rule objects with their names displayed in lbRules.
Trouble I am having is binding the SelectedRule property to lbRules' SelectedItem. I tried binding a textblock's text property to SelectedRule but it is always null.
<TextBlock Text="{Binding Path=SelectedRule.Name}" />
The error I'm seeing in the output window is:
BindingExpression path error: 'SelectedRule' property not found.
Can anyone help me with this binding - I can't see why it shouldn't find the SelectedRule property.
I then tried changing the textblock's text property as bellow, which works. Trouble is I want to use the SelectedRule in my ViewModel.
<TextBlock Text="{Binding ElementName=lbRules, Path=SelectedItem.Name}" />
Thanks very much for your help.
First off, you need to implement INotifyPropertyChanged interface in your view model and raise the PropertyChanged event in the setter of the Rule property. Otherwise no control that binds to the SelectedRule property will "know" when it has been changed.
Then, your XAML
<TextBlock Text="{Binding Path=SelectedRule.Name}" />
is perfectly valid if this TextBlock is outside the ListBox's ItemTemplate and has the same DataContext as the ListBox.
Inside the DataTemplate you're working in the context of a Rule, that's why you cannot bind to SelectedRule.Name -- there is no such property on a Rule.
To bind to the original data context (which is your ViewModel) you can write:
<TextBlock Text="{Binding ElementName=lbRules, Path=DataContext.SelectedRule.Name}" />
UPDATE: regarding the SelectedItem property binding, it looks perfectly valid, I tried the same on my machine and it works fine. Here is my full test app:
XAML:
<Window x:Class="TestWpfApplication.ListBoxSelectedItem"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="ListBoxSelectedItem" Height="300" Width="300"
xmlns:app="clr-namespace:TestWpfApplication">
<Window.DataContext>
<app:ListBoxSelectedItemViewModel/>
</Window.DataContext>
<ListBox ItemsSource="{Binding Path=Rules}" SelectedItem="{Binding Path=SelectedRule, Mode=TwoWay}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Name:" />
<TextBox Text="{Binding Name}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Window>
Code behind:
namespace TestWpfApplication
{
/// <summary>
/// Interaction logic for ListBoxSelectedItem.xaml
/// </summary>
public partial class ListBoxSelectedItem : Window
{
public ListBoxSelectedItem()
{
InitializeComponent();
}
}
public class Rule
{
public string Name { get; set; }
}
public class ListBoxSelectedItemViewModel
{
public ListBoxSelectedItemViewModel()
{
Rules = new ObservableCollection<Rule>()
{
new Rule() { Name = "Rule 1"},
new Rule() { Name = "Rule 2"},
new Rule() { Name = "Rule 3"},
};
}
public ObservableCollection<Rule> Rules { get; private set; }
private Rule selectedRule;
public Rule SelectedRule
{
get { return selectedRule; }
set
{
selectedRule = value;
}
}
}
}
Yocoder is right,
Inside the DataTemplate, your DataContext is set to the Rule its currently handling..
To access the parents DataContext, you can also consider using a RelativeSource in your binding:
<TextBlock Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ____Your Parent control here___ }}, Path=DataContext.SelectedRule.Name}" />
More info on RelativeSource can be found here:
http://msdn.microsoft.com/en-us/library/system.windows.data.relativesource.aspx
For me, I usually use DataContext together in order to bind two-depth property such as this question.
<TextBlock DataContext="{Binding SelectedRule}" Text="{Binding Name}" />
Or, I prefer to use ElementName because it achieves bindings only with view controls.
<TextBlock DataContext="{Binding ElementName=lbRules, Path=SelectedItem}" Text="{Binding Name}" />
There is a shorter version to bind to a selected item's property:
<TextBlock Text="{Binding Rules/Name}" />
since you set your itemsource to your collection, your textbox is tied to each individual item in that collection. the selected item property is useful in this scenario if you were trying to do a master-detail form, having 2 listboxes. you would bind the second listbox's itemsource to the child collection of rules. in otherwords the selected item alerts outside controls that your source has changed, internal controls(those inside your datatemplate already are aware of the change.
and to answer your question yes in most circumstances setting the itemsource is the same as setting the datacontext of the control.