in my WPF app I have a custom control with a dependency object
public static readonly DependencyProperty SomeFieldProperty =
DependencyProperty.Register("SomeField", typeof(double), typeof(MyControl), new PropertyMetadata((double)0, OnPropChanged));
public double SomeField
{
get { return (double)GetValue(SomeFieldProperty ); }
set { SetValue(SomeFieldProperty , value); }
}
And from my XAML I'm trying to bind to SomeField like below but it doesn't work:
UPDATED:
<UserControl.Template>
<ControlTemplate TargetType="ContentControl">
<WrapPannel >
<abc:MyControl SomeField="{Binding SomeValue, Mode=TwoWay}" />
</WrapPannel>
</ControlTemplate>
</UserControl.Template>
Tried different solutions suggested in this like questions in the StackOverflow but none of them worked. Maybe my case is a specific one as I am trying to bind from within a template?
Looks like it is not a binding problem. Actually the Template property of a UserControl is overrideb by InitializeComponent().
Something like this will work:
<UserControl x:Class="WPF.MyUserControl"
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"
xmlns:local="clr-namespace:WPF"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<WrapPannel>
<abc:MyControl SomeField="{Binding SomeValue, Mode=TwoWay}" />
</WrapPannel>
</UserControl>
Actually UserControls are to be used when Templates are not needed. Otherwise use Controls, ContentControls or ItemsControls.
Related
We have a TickerUserControl with a simple Text property which stands for the displayed text of the ticker.
Do we really have to use these DependencyProperty pattern thing inside the UserControl (see below) or is there a simpler way to achieve this?
When we want to use our UserControl and BIND the text field to a property of a ViewModel we have to use the following weird binding syntax. Why can't we just use 'Text="{Binding Text}"' like all the other controls? Is there something wrong with the property implementation of the UserControl or something?
Usage of the UserControl
<userControls:TickerUserControl Text="{Binding Path=Parent.DataContext.TickerText, RelativeSource={RelativeSource Self}, Mode=OneWay}"/>
Property implementation of the UserControl (code behind)
public partial class TickerUserControl : UserControl
{
public string Text
{
get { return (string)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
public static readonly DependencyProperty TextProperty = DependencyProperty.Register("Text", typeof(string), typeof(TickerUserControl), new PropertyMetadata(""));
// ...
}
XAML snippet of the UserControl
<UserControl x:Class="Project.UserControls.TickerUserControl"
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"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
mc:Ignorable="d">
<TextBlock Text="{Binding Text}">
<!-- ... -->
The solution
The problem was the setting of the DataContext inside the UserControl.
I deleted the DataContext binding added a name to the UserControl and modified the TextBox binding inside the UserControl. After that I was able to bind "as usual" from outside.
<userControls:TickerUserControl Text="{Binding TickerText}"/>
<UserControl x:Class="Project.UserControls.TickerUserControl"
Name="TickerUserControl"
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">
<TextBlock Text="{Binding Text, ElementName=TickerUserControl}">
<!-- ... -->
If you want to bind your property, you'll need a dependency property.
To solve the weird binding you can do the following changes:
In your usercontrol
<UserControl Name="control"...
<TextBlock Text="{Binding Text, ElementName=control}">
And then you can bind it like that
<userControls:TickerUserControl Text="{Binding TickerText}"/>
If you want to create bindable properties in the code behind of your UserControl, then yes, you do have to use DependencyProperty objects. However, you don't have to create your bindable properties there... you could use an MVVM type pattern and create your bindable properties in a separate class as long as you set that class as the DataContext of you UserControl.
No, you don't have to use that 'weird' binding syntax... the problem is that you have hard coded setting the DataContext of your UserControl to its code behind. Instead of doing that, you can bind your Text DependencyProperty in the control like this:
<TextBlock Text="{Binding Text, RelativeSource={RelativeSource FindAncestor,
{AncestorType={x:Type Local:TickerUserControl}}}" />
Local is the XML namespace of your local project... something like this:
xmlns:Local="clr-namespace:Project.UserControls.TickerUserControl"
Then after removing the DataContext binding, you should be able to bind to the control from outside normally.
In a Wpf Application i have a main window.
I have added a user control to the same project.
In the user control's .xaml.cs file a Dependency property ( "Value" name of the property ) is added.
I would like to access the defined dependency property in the usercontrol.xaml.
I know i can do the same while creating the control instance either in window.xaml or some other user control.
But is it possible to access the dependency property defined in .xaml.cs in .xaml?
Question updated based on Vivs answer
Ok. I mentioned my question wrongly. Nevertheless even i was not aware of accessing. But my actual intended question is it possible to set the dependency property from .xaml. some thing like from the example given above,
<Grid CustomBackground ="{Binding Path= BackgroundColor}" />
Or
<Grid CustomBackground ="Blue" />
Is it possible to set the custom dependency properties like this in the same .xaml?
Yes it is possible.
something like:
.xaml
<UserControl x:Class="MvvmLight26.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:MvvmLight26"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid Background="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:UserControl1}}, Path=CustomBackground}" />
</UserControl>
and .xaml.cs:
public partial class UserControl1 : UserControl {
public static readonly DependencyProperty CustomBackgroundProperty =
DependencyProperty.Register(
"CustomBackground",
typeof(Brush),
typeof(UserControl1),
new FrameworkPropertyMetadata(Brushes.Tomato));
public UserControl1() {
InitializeComponent();
}
public Brush CustomBackground {
get {
return (Brush)GetValue(CustomBackgroundProperty);
}
set {
SetValue(CustomBackgroundProperty, value);
}
}
}
Alternate:
If you say have the DataContext of the UserControl as itself like:
public UserControl1() {
InitializeComponent();
DataContext = this;
}
then in your xaml you could just go with:
<Grid Background="{Binding Path=DataContext.CustomBackground}" />
Update:
For the new question,
Not quite directly.
You can "set" the value if the custom DP is registered as an attached property(Do remember an attached property is not the same as a normal DP in it's behavior and scope.)
If you want to keep it as a normal DP, then you can keep UserControl1 from the original answer same as it is(just the DP part. You need to remove the xaml part of it and make it a non-partial class in the code-behind) and then derive it to a new UserControl.
something like:
<local:UserControl1 x:Class="MvvmLight26.UserControl2"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:MvvmLight26"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
CustomBackground="Blue"
mc:Ignorable="d">
<Grid />
</local:UserControl1>
You can ofc name UserControl1 as something like "BaseUserControl" or so to make it obvious that it's not intended for direct usage.
You can set the value from the UserControl.Style in the same xaml as well.
xaml:
<UserControl x:Class="MvvmLight26.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:MvvmLight26"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<UserControl.Style>
<Style>
<Setter Property="local:UserControl1.CustomBackground"
Value="Blue" />
</Style>
</UserControl.Style>
<Grid Background="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:UserControl1}}, Path=CustomBackground}" />
</UserControl>
I'm sure this is a real beginner question; I'm just having trouble figuring out how to search for it.
I have a simple UserControl (MyNewControl) that only has three controls, one of which is the following label:
<sdk:Label x:Name="Title" />
In another control, then, I want to use MyNewControl, like this:
<local:MyNewControl Grid.Column="1" x:Name="MyNewGuy" />
What do I need to do so that this second control can, for example, set a gradient background for my Title label?
First you define the desired dependency property in your UserControl:
public partial class MyUserControl : UserControl
{
public Brush LabelBackground
{
get { return (Brush)GetValue(LabelBackgroundProperty); }
set { SetValue(LabelBackgroundProperty, value); }
}
public static readonly DependencyProperty LabelBackgroundProperty =
DependencyProperty.Register("LabelBackground", typeof(Brush), typeof(MyUserControl), new PropertyMetadata(null));
public MyUserControl()
{
InitializeComponent();
}
}
To assign the value of your property to the child label, you can bind using the ElementName property of the binding:
<UserControl x:Class="SilverlightApplication1.MyUserControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
d:DesignHeight="300"
d:DesignWidth="400"
mc:Ignorable="d"
x:Name="UserControl"
>
<Grid x:Name="LayoutRoot">
<sdk:Label x:Name="Title"
HorizontalAlignment="Center"
VerticalAlignment="Center" Content="Title" Background="{Binding LabelBackground, ElementName=UserControl}" />
</Grid>
</UserControl>
As you are using Silverlight 5, you can also set a RelativeSource to your binding, instead of internally naming your UserControl:
<sdk:Label Background="{Binding LabelBackground, RelativeSource={RelativeSource AncestorType=UserControl}}" />
Then, when using your UserControl, you just set (or bind) the LabelBackground to the desired value:
<local:MyUserControl LabelBackground="Red"/>
Just to note, you can also create a CustomControl instead of a UserControl, add the dependency property to it the same way and use a TemplateBinding when defining its template.
You can do that using dependency property in your custom control . Say you defined LableBG as an dependency property in your custom control and do the binding with an Background of your defined Label control in xaml . And when you use your custom control in another control you can set the LableBG of it from xaml or else from code behind.
Note : the type of your defined dependency property should be of Brush
For eg :
Defining Dependency Property in cs file of your custom control :
/1. Declare the dependency property as static, readonly field in your class.
public static readonly DependencyProperty LableBGProperty = DependencyProperty.Register(
"LableBG", //Property name
typeof(Brush), //Property type
typeof(MySilverlightControl), //Type of the dependency property provider
null );//Callback invoked on property value has changes
<sdk:Label x:Name="Title" Background="{Binding LableBG }" /> (Custom Control)
<local:MyNewControl Grid.Column="1" x:Name="MyNewGuy" LableBG="Red" /> (Another control)
Having a simple XAML user control, I'd like to set the DataContext to the code behind (xaml.cs) file.
I'd like to set DataContext and Itemssource in XAML, so I can populate the combobox with property ListOfCars
XAML
<UserControl x:Class="Sample.Controls.MyControl"
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="85" d:DesignWidth="200">
<Grid Height="85" Width="200" Background="{StaticResource MainContentBackgroundBrush}">
<StackPanel Orientation="Vertical">
<ComboBox Height="23.338" x:Name="CarList" />
</StackPanel>
</Grid>
</UserControl>
Code behind
public List<Cars> ListOfCars
{
get { return _store.ListCars(); }
}
In other words, instead of doing this in codebehind, how may I set the binding in XAML
public MyControl()
{
InitializeComponent();
_store = new Store();
CarList.ItemsSource = _store.ListCars();
CarList.DisplayMemberPath = "Name";
}
Just bind the ItemsSource.
<ComboBox ItemsSource="{Binding ListOfCars}"/>
And then for the UserControl:
<MyControl DataContext="{Binding *viewModel*}"/>
You have to bind the DataContext where your UserControl is used rather than in the definition, because in the definition you don't know to what to bind. The Combobox automatically is in the context of the control so you can just bind to the DataContext without any additional work.
Example of binding to a resource:
<Application.Resources>
...
<viewmodels:ViewModelLocator x:Key="ViewModelLocator"/>
...
</Application.Resources>
<MyControl DataContext="{Binding Source={StaticResource ViewModelLocator}}"/>
This creates an instance of the ViewModelLocator and then binds the DataContext of the control to that resource.
Do not do that, you will mess up all external bindings to the DataContext. Use UserControl.Name and ElementName bindings instead (or RelativeSource).
I'm new in WPF and I'm creating a control. This control contains a DataGrid and some other WPF controls.
I created my Control as below:
<UserControl x:Class="MyControls.MyControl"
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="329" d:DesignWidth="535" >
<Grid>
<DataGrid Margin="6,25,6,35" Name="dataGrid" SelectionUnit="CellOrRowHeader" x:FieldModifier="public" HeadersVisibility="All"/>
<OtherControl HorizontalAlignment="Left" x:Name="otherControl" Height="34" VerticalAlignment="Bottom" Width="523" x:FieldModifier="private"/>
<Label Content="caption" Height="24" HorizontalAlignment="Left" Name="captionLabel" VerticalAlignment="Top" Foreground="#FF2626D1" x:FieldModifier="private"/>
</Grid>
</UserControl>
So, everything goes well so far, then I create a container UserControl which has in it my control created previously:
<UserControl x:Class="MyContainers.MyContainer"
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" xmlns:my="clr-namespace:MyControls">
<Grid>
<my:MyControl>
</my:MyControl>
</Grid>
What I can not do is the following:
<my:MyControl>
<my:MyControl.dataGrid>
</my:MyControl.dataGrid>
</my:MyControl>
I previously set the datagrid's property of FieldModifier as public in order to get access to it in another xaml, but it raises an error from visual studio.
I need to "expose" my dataGrid in order to be able to add columns and their styles.
I would like to be able to do something like this:
<my:MyControl.dataGrid.Columns >
<DataGridTextColumn />
<DataGridTextColumn />
...
<DataGridTextColumn />
</my:MyControl.dataGrid.Columns>
So, is not enough to set the datagrid's property of FieldModifier as public?
Do I need to do something else? How can I achieve this? Is this even possible?
I hope someone can help me. Thank you in advance.
You cannot access the child DataGrid as MyControl.dataGrid -- MyControl has no property named "dataGrid".
You might try adding a dependency property of type ObservableCollection<DataGridColumn> to MyControl, and modify the dataGrid columns whenever that collection changes.
EDIT:
Whipped together a quick example for you:
UserControl code:
public partial class UserControl1 : UserControl
{
public static readonly DependencyProperty ColumnsProperty = DependencyProperty.Register("Columns", typeof(ObservableCollection<DataGridColumn>), typeof(UserControl1));
public ObservableCollection<DataGridColumn> Columns
{
get { return (ObservableCollection<DataGridColumn>)GetValue(ColumnsProperty); }
set { SetValue(ColumnsProperty, value); }
}
public UserControl1()
{
Columns = new ObservableCollection<DataGridColumn>();
Columns.CollectionChanged += (s, a) =>
{
dataGrid.Columns.Clear();
foreach (var column in this.Columns)
dataGrid.Columns.Add(column);
};
InitializeComponent();
}
}
UserControl xaml:
<UserControl x:Class="WpfApplication1.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">
<Grid>
<DataGrid x:Name="dataGrid" AutoGenerateColumns="False"/>
</Grid>
so you can use it like:
<Grid>
<l:UserControl1>
<l:UserControl1.Columns>
<DataGridTextColumn Header="Col1"/>
<DataGridTextColumn Header="Col2"/>
</l:UserControl1.Columns>
</l:UserControl1>
</Grid>