Scenario:
I have a view that has some DataTemplate resources
<DataTemplate x:Key="myDragCueTemplate">
<Border Background="Blue"
Opacity="0.5"
Width="250">
<TextBlock Text="{Binding}" HorizontalAlignment="Left"></TextBlock>
</Border>
</DataTemplate>
I have a custom control derived from ListBox. Inside the custom listbox on a certain event I want to fetch a datatemplate from the View's resources.
public class MyListBox : ListBox
{
public MyListBox()
{
this.DefaultStyleKey = typeof(MyListBox);
}
...
itemDragCue.ContentTemplate = this.Resources["myDragCueTemplate"] as DataTemplate;
...
I tried adding the datatemplates to a separate .xaml file and added a ResourceDictionary, but it still didn't pick it up.
How can I get the resource in the custom control's backend?
Thanks.
this.Resources will only give the resources declared in
<UserControl x:Class="MyListbox">
<UserControl.Resources>
I would recommend putting myDragCueTemplate in a ResourceDictionary. You will then have to read that ResourceDictionary in in your code behind, and extract the specific resource you want.
Try this
const string resourcesPath = "/AssemblyName;component/Resources.xaml";
Uri resourceUri = new Uri(resourcesPath, UriKind.Relative);
StreamResourceInfo sri = Application.GetResourceStream(resourceUri);
StreamReader sr = new StreamReader(sri.Stream);
ResourceDictionary dictionary = (ResourceDictionary) XamlReader.Load(sr.ReadToEnd());
itemDragCue.ContentTemplate = dictionary["myDragCueTemplate"] as DataTemplate;
Related
X problem.
I want to enlarge (let it take whole available space) a part of window content temporarily.
Window layout is pretty complicated: many nested panels, splitters, content to enlarge is 10 levels deep. Changing Visibility to stretch content is simply not enough (thanks to splitters) and seems very complicated.
Y problem
I decide to move that content into a user control and do something like (pseudo-code)
if(IsEnlarged)
{
oldContent = window.Content; // store
window.Content = newContent;
}
else
window.Content = oldContent; // restore
No problems. It was working perfectly in test project ... until I start using data templates.
Problem: if data templates are used then as soon as window.Content = newContent occurs, then that newContent.DataContext is lost and become the same as window.DataContext. This will trigger various binding errors, attached behaviors suddenly changes to default value, etc.. all kind of bad stuff.
Question: why DataContext is changing? How to prevent/fix this issue?
Here is a repro (sorry, can't make it any shorter):
MainWindow.xaml contains
<Window.Resources>
<DataTemplate DataType="{x:Type local:ViewModel}">
<local:UserControl1 />
</DataTemplate>
</Window.Resources>
<Grid Background="Gray">
<ContentControl Content="{Binding ViewModel}" />
</Grid>
MainWindow.cs contains
public ViewModel ViewModel { get; } = new ViewModel();
public MainWindow()
{
InitializeComponent();
DataContext = this;
}
UserControl1.xaml contains
<Button Width="100"
Height="100"
CommandParameter="{Binding RelativeSource={RelativeSource Self}}"
Command="{Binding Command}" />
ViewModel (using DelegateCommand)
public class ViewModel
{
public DelegateCommand Command { get; set; }
bool _set;
object _content;
public ViewModel()
{
Command = new DelegateCommand(o =>
{
var button = (Button)o;
var window = Window.GetWindow(button);
_set = !_set;
if (_set)
{
_content = window.Content;
var a = button.DataContext; // a == ViewModel
window.Content = button;
var b = button.DataContext; // b == MainWindow ??? why???
}
else
window.Content = _content;
});
}
}
Set breakpoint on var a = ..., start program, click the button, do steps and observe button.DataContext as well as binding error in Output window.
ok here some general thoughts.
if you bind a object(viewmodel) to the Content property of the contentcontrol then wpf uses a DataTemplate to visualize the object. if you dont have a DataTemplate you just see object.ToString(). DataContext inheritance means that the DataContext is inherited to the child elements. so a real usercontrol will inherit the DataContext from the parent. the are common mistakes you find here on stackoverflow when creating UserControls - they often break DataContext inheritance and set the DataContext to self or a new DataContext.
UserControl DataContext Binding
You must be trying to use your DataTemplate as ContentTemplate for your ContentControl. As ContentTemplate operates on Content, so it will use Content as its DataContext. And your Content contains ViewModel.
Once your Button is no longer part of your DataTemplate, so it will use MainWindow's DataContext.
No seeing your comments, I am assuming that you want DataContext of UserControl to remain intact, even if your UserControl is not part of DataTemplate.
So, simple set DataContext of Button explicitly using XAML using RelativeSource.
Example,
<Button Content="{Binding Data}" DataContext="{Binding vm1, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}" />
Playing with DataContext in code is not a good idea.
I used the following post to implement a datagrid bound to a list of dynamic objects
Binding DynamicObject to a DataGrid with automatic column generation?
The ITypedList method GetItemProperties works fine, a grid is displayed with all the columns I described.
I use a custom PropertyDescriptor and override the GetValue and SetValue methods as described in the above post, I also implement the TryGetMember and TrySetMember methods in the dynamic objects.
so basically I have a ComplexObject:DynamicCobject with a field Dictionary and a ComplexObjectCollection implementing ITypedList and IList.
This all works fine except when I bind the itemsSource of the DataGrid to the collection, the cells will show the SimpleObject type name and I actually want to implement a template to show the property Value of the SimpleObject in a text block.
I've used all sorts of methods to try and get the underlying SimpleObject but nothing works and I always get the ComplexObject for the row. I am using autogenerated columns and this always seems to produce a text column, this may be the problem but why cant I still get the underlying SimpleObject from somewhere in the cell properties?
Below would be my ideal solution but this does not work.
<Grid>
<Grid.Resources>
<DataTemplate x:Key="DefaultNodeTempate">
<ContentControl Content="{Binding RelativeSource={RelativeSource TemplatedParent},
Path=Content}">
<ContentControl.Resources>
<DataTemplate DataType="local:SimpleObjectType">
<TextBlock Text="{Binding Value}" />
</DataTemplate>
</ContentControl.Resources>
</ContentControl>
</DataTemplate>
</Grid.Resources>
<DataGrid ItemsSource="{Binding ElementName=mainWin, Path=DynamicObjects}">
<DataGrid.Resources>
<Style TargetType="DataGridCell">
<Setter Property="ContentTemplate" Value="{StaticResource DefaultNodeTempate}" />
</Style>
</DataGrid.Resources>
</DataGrid>
</Grid>
Any suggestions would be much appreciated.
Thanks
Kieran
So I found the solution was to do some work in the code behind.
In the AutoGeneratingColumn event create a DataTemplate with a content control and a custom template selector (I create the selector in Xaml and found it as a resource).
Create a binding for the ContentProperty of the ContentControl with e.PropertyName as the path
Create a new DataGridTemplateColumn and set the new columns CellTemplate to your new DataTemplate
replace e.Column with your new column and hey presto the cells datacontext bind with the dynamic property for that column.
If anyone has any refinement to this please feel free to share your thoughts.
Thanks
EDIT: As requested some sample code for my solution
Custom template selector:
public class CustomDataTemplateSelector : DataTemplateSelector
{
public List<DataTemplate> Templates { get; set; }
public CustomDataTemplateSelector()
: base()
{
this.Templates = new List<DataTemplate>();
}
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
DataTemplate template = null;
if (item != null)
{
template = this.Templates.FirstOrDefault(t => t.DataType is Type ? (t.DataType as Type) == item.GetType() : t.DataType.ToString() == item.GetType().ToString());
}
if (template == null)
{
template = base.SelectTemplate(item, container);
}
return template;
}
}
XAML:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication1"
Title="MainWindow" Height="350" Width="525">
<Grid x:Name="ParentControl">
<Grid.Resources>
<local:CustomDataTemplateSelector x:Key="MyTemplateSelector" >
<local:CustomDataTemplateSelector.Templates>
<DataTemplate DataType="{x:Type local:MyCellObject}" >
<TextBox Text="{Binding MyStringValue}" IsReadOnly="{Binding IsReadOnly}" />
</DataTemplate>
</local:CustomDataTemplateSelector.Templates>
</local:CustomDataTemplateSelector>
</Grid.Resources>
<DataGrid ItemsSource="{Binding Rows}" AutoGenerateColumns="True" AutoGeneratingColumn="DataGrid_AutoGeneratingColumn" >
</DataGrid>
</Grid>
</Window>
Code behind:
private void DataGrid_AutoGeneratingColumn(object sender, DataGridAutoGeneratingColumnEventArgs e)
{
// Get template selector
CustomDataTemplateSelector selector = ParentControl.FindResource("MyTemplateSelector") as CustomDataTemplateSelector;
// Create wrapping content control
FrameworkElementFactory view = new FrameworkElementFactory(typeof(ContentControl));
// set template selector
view.SetValue(ContentControl.ContentTemplateSelectorProperty, selector);
// bind to the property name
view.SetBinding(ContentControl.ContentProperty, new Binding(e.PropertyName));
// create the datatemplate
DataTemplate template = new DataTemplate { VisualTree = view };
// create the new column
DataGridTemplateColumn newColumn = new DataGridTemplateColumn { CellTemplate = template };
// set the columns and hey presto we have bound data
e.Column = newColumn;
}
There may be a better way to create the data template, I have read recently that Microsoft suggest using a XamlReader but this is how I did it back then. Also I haven't tested this on a dynamic class but I'm sure it should work either way.
I'm building a custom UserControl in WPF, which has a ViewModel associated. I also want do dynamically make controls in the code behind. But now I'm having problems binding the generated controls with the ViewModel properties. My code is:
<UserControl x:Class="SVT.Teste.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300"
DataContext="UserControl1ViewModel">
<Grid Name="GridContainer">
</Grid>
</UserControl>
and code behind:
public UserControl1()
{
InitializeComponent();
System.Windows.Controls.Button newBtn = new Button();
newBtn.SetBinding(Button.ContentProperty, new Binding("Test"));
GridContainer.Children.Add(newBtn);
}
public class UserControl1ViewModel
{
private string test = "ola";
public string Test
{
get { return test; }
}
}
When I run this I get:
"System.Windows.Data Error: 40 : BindingExpression path error: 'Test'
property not found on 'object' ''String' (HashCode=-946585093)'.
BindingExpression:Path=Test; DataItem='String' (HashCode=-946585093);
target element is 'Button' (Name=''); target property is 'Content'
(type 'Object')"
Can you help me?
You are setting DataContext property of UserControl1 to a string instead of your view model instance.
You need to do something like this:
<UserControl xmlns:local="clr-namespace:NAMESPACE_WHERE_VIEWMODEL_IS_DEFINED">
<UserControl.DataContext>
<local:UserControl1ViewModel />
</UserControl.DataContext>
<!-- unrelated code omitted -->
</UserControl>
You are setting you DataContext to the type, not an instance that has the properties.
In your method that creates the user control do :
public UserControl1()
{
InitializeComponent();
System.Windows.Controls.Button newBtn = new Button();
newBtn.SetBinding(Button.ContentProperty, new Binding("Test"));
GridContainer.Children.Add(newBtn);
**DataContext = new UserControl1ViewModel();**
}
You still have more work to do. The way you have it no notifications or update will happen. Implement the INotifyPropertyChanged interface (on UserControlViewModel). And remove setting DataContext in the XAML to the type.
try with this binding
Binding MyBinding = new Binding();
MyBinding.Path = new PropertyPath("Test");
newBtn.DataContext = new UserControl1ViewModel(); //or MyBinding.Source = new //UserControl1ViewModel();
newBtn.SetBinding(Button.ContentProperty, MyBinding);
max is right, but i have another question. why do you want create your usercontrol dynamic when you have a viemwodel you wanna bind to? makes no sense to me. let me explain:
if you have a viewmodel - you know in mind how this viewmodel should be rendered and what the bindings are. so you could create a usercontrol/view for this viewmodel
MyUserControl1View.xaml
<UserControl>
<Grid>
<Button Content="{Binding Test}"/>
<!-- more controls and binding if the viewmodel expose more-->
</Grid>
</UserControl>
so what you have now is a representation of your viewmodel. they are not connnected but your viewmodel should look like this and the binding are set. till now no datacontext is set at all.
all you have to do now is to go the viewmodel first approach and the use of datatemplates.
let us assume the following in your mainwindow
<Window>
<Window.Resources>
<DataTemplate Datatype="{x:Type local:Usercontrol1viewmodel}">
<view:MyUserControl1View/>
</DataTemplate>
</Window.Resources>
now wpf knows how to render Usercontrol1viewmodel.
one step more in your mainwindow viewmodel you handle your Usercontrol1viewmodel.
public Usercontrol1viewmodel MyWhatEver {get;set;}
if you bind this property to a contentpresenter, you will see the wpf magic;)
<ContentPresenter Content="{Binding MyWhatEver}"/>
now you see the MyUserControl1View in the contentpresenter, no dynamic view code needed. just go with your viewmodels.
ps: feel free to edit my bad english.
I am trying to find out how to set correctly multiple DataContexts in XAML page. I have a basic collection that I create in code behind and set ItemSource Binding og AutoCompleteBox to it. At the same time, I have another datacontext to set labelsDataSource inside the grid. If I set this datacontext, the AutoCompleteBox’s itemsSource binding is lost. AutoCompleteBox is inside that grid. I do assign DataContext directly to the objetc this way:
MyAutoCompleteBox.DataContext = this;
I am wondering if there is a better way to do it?
Thank you in advance for the help!
Setting AutoComplete Box:
<sdk:AutoCompleteBox x:Name="MyAutoCompleteBox" IsTextCompletionEnabled="True" ItemsSource="{Binding Items}" />
Code Behind:
public IList<string> Items
{
get;
private set;
}
public Basic_ChildWindow()
{
InitializeComponent();
Items = new List<string>();
Items.Add(#"One");
Items.Add(#"Two");
Items.Add(#"Three");
DataContext = this;
}
Another datacontext in the same XAML page, AutoCompleteBox is inside that grid:
<Grid x:Name="grdBasic_ChildWindow_Right" Style="{StaticResource GridStyle}" DataContext="{Binding Source={StaticResource LabelsDataSource}}">
I'm not sure I understand your question--what is "labelsDataSource"?
However, if what you have posted is all the code and there is nothing more to it, simply remove the datacontext/binding from the grid. The grid does not need a datacontext set (it is simply a visual container--not data-related).
So change this:
<Grid x:Name="grdBasic_ChildWindow_Right" Style="{StaticResource GridStyle}" DataContext="{Binding Source={StaticResource LabelsDataSource}}">
To this:
<Grid x:Name="grdBasic_ChildWindow_Right" Style="{StaticResource GridStyle}">
I know its strange what I am doing but I want this to work. I am going wrong somehwere I feel.
I have a DataTemplate defined in my resources as follows :
<UserControl.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="../ParameterEditorResourceDictionary.xaml"></ResourceDictionary>
<ResourceDictionary>
<DataTemplate x:Key="ParameterDefault">
<StackPanel Orientation="Horizontal">
<TextBlock Text="("></TextBlock>
<ItemsControl ItemsSource="{//I need to set from code}">
//some code here
</ItemsControl>
<TextBlock Text=")"></TextBlock>
</StackPanel>
</DataTemplate>
</ResourceDictionary>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</UserControl.Resources>
I have a DataGrid defined in my xaml which has a loaded event.
<cc:PEDataGrid AutoGenerateColumns="False"
Loaded="CommonPEGrid_Loaded">
</cc:PEDataGrid>
In my event handler code I want to set the ItemsSource of ItemsControl defined in my DataTemplate. My code behind looks like this :
private void CommonPEGrid_Loaded(object sender, RoutedEventArgs e)
{
int i = 0;
DataGrid dg = sender as DataGrid;
DataGridTemplateColumn column = null;
//ParametersAllLoops is a ObservableCollection
foreach (ParameterLoop obj in ParametersAllLoops)
{
column = new DataGridTemplateColumn();
column.Header = "Loop ( " + i.ToString() + " )";
DataTemplate dt = null;
//Here I want to write code
//I want to access the DataTemplate defined in resources
//and set the ItemsSource of ItemsControl to something like this
// xxx.ItemsSource = obj; and then assign the DataTemplate to
//the CellTemplate of column.
//**Note :: ParameterLoop object has the IList Parameters**
column.CellTemplate = dt;
dg.Columns.Add(column);
i++;
}
}
You can find the resource by using method FindResource() and cast it to DataTemplate but to assign it ItemSource you will need string manipulation.
It seems you want to have dynamic columns on your datagrid, I would suggest that you have that generate the datatemplate in code behind so that you can resolve your binding paths and source names there and then attach it as cell template or cell edit template.