Develop Reference

WPF tooltip Binding getting override when I set the tooltip from code

I have a User control and I bind the tooltip of that control into some object's property
<usercontrols:ucButton x:Name="xSaveCurrentBtn" ButtonType="ImageButton" ButtonFontImageSize="16" ButtonImageWidth="18" ButtonImageHeight="18" ButtonImageType="Save" Click="xSaveSelectedButton_Click" ButtonStyle="{StaticResource $ImageButtonStyle_Menu}" DockPanel.Dock="Right" HorizontalAlignment="Right" VerticalAlignment="Center" Margin="0,0,0,0">
<usercontrols:ucButton.ToolTip>
<ToolTip Content="{Binding ItemName, Mode=OneWay}" ContentStringFormat="Save {0}"/>
</usercontrols:ucButton.ToolTip>
</usercontrols:ucButton>
from the code I set the data context of the ucButton to be my object:
xSaveCurrentBtn.DataContext = WorkSpace.Instance.CurrentSelectedItem;
sometimes the CurrentSelectedItem is null, and if this is the case I want the tooltip to display "No Item Selected"
I tried doing this:
xSaveCurrentBtn.Tooltip = "No Item Selected";
but when the CurrentSelectedItem isn't null and I reset the xSaveBtn.DataContext to that object, I am still seeing the No Item Selected tooltip as if my WPF tooltip section was overriden and its no longer binding into the datacontext ItemName Property

You are trying to set a property to two values at the same time. It's impossible.
What you are doing in XAML is equivalent to:
xSaveCurrentBtn.Tooltip = new ToolTip() {.....};
When you setting a string value to the same property, the previous value is lost. And it is not possible to restore it if you do not save it first.
You might want to assign a value in case of a binding error:
<ToolTip Content="{Binding ItemName,
Mode=OneWay,
FallbackValue='No Item Selected'}"
ContentStringFormat="Save {0}"/>
how can I bind the data context to update to be the new CurrentSelectedItem without explicitly setting it?
Assuming that «WorkSpace.Instance» is an immutable property that returns an instance of «WorkSpace» and «CurrentSelectedItem» is a property with an «INotifyPropertyChanged.PropertyChanged» notification, then you can do this:
<usercontrols:ucButton DataContext="{Binding CurrentSelectedItem, Source={x:Static viewmodels:WorkSpace.Instance}}" ...>
The «viewmodels» prefix depends on the assembly and namespace in which the «WorkSpace» class is declared.

you can use ContentTemplate with TextBlock, which will either use StringFormat, or TargetNullValue depending on ItemName being null:
<usercontrols:ucButton.ToolTip>
<ToolTip Content="{Binding ItemName}">
<ToolTip.ContentTemplate>
<DataTemplate>
<TextBlock Text="{Binding StringFormat='Save {0}',
TargetNullValue='No Item Selected'}"/>
</DataTemplate>
</ToolTip.ContentTemplate>
</ToolTip>
</usercontrols:ucButton.ToolTip>
or if you bind Tooltip.Content differently:
<usercontrols:ucButton.ToolTip>
<ToolTip Content="{Binding}">
<ToolTip.ContentTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=ItemName,
StringFormat='Save {0}',
FallbackValue='No Item Selected'}"/>
</DataTemplate>
</ToolTip.ContentTemplate>
</ToolTip>
</usercontrols:ucButton.ToolTip>

How do I pass an input via binding to a custom property in UserControl? [duplicate]

I have a UserControl that I want to participate in data binding. I've set up the dependency properties in the user control, but can't get it work.
The uc displays the correct text when I call it with static text (e.g BlueText="ABC") . When i try to bind it to a local public property, it is always blank.
<src:BlueTextBox BlueText="Feeling blue" /> <!--OK-->
<src:BlueTextBox BlueText="{Binding Path=MyString}" /> <!--UserControl always BLANK!-->
<TextBox Text="{Binding Path=MyString}" Width="100"/> <!--Simple TextBox Binds OK-->
I've boiled the code down to the following simplified example. Here is the XAML of the UserControl:
<UserControl x:Class="Binding2.BlueTextBox" ...
<Grid>
<TextBox x:Name="myTextBox" Text="{Binding BlueText}" Foreground="Blue" Width="100" Height="26" />
</Grid>
Here is the code behind of the UserControl:
public partial class BlueTextBox : UserControl
{
public BlueTextBox()
{
InitializeComponent();
DataContext = this; // shouldn't do this - see solution
}
public static readonly DependencyProperty BlueTextProperty =
DependencyProperty.Register("BlueText", typeof(string), typeof(BlueTextBox));
public string BlueText
{
get { return GetValue(BlueTextProperty).ToString(); }
set { SetValue( BlueTextProperty, value.ToString() ); }
}
This seems like it should be really easy, but I can't make it work. Thanks for your help!
More info: When i was trying the fix suggested by Eugene, I noticed some peculiar behavior. I added a PropertyChangedCallback to the metadata; this allows me to watch the value of BlueText getting set. When setting the string to a static value (="feeling blue") the PropertyChanged event fires. The data binding case does not fire PropertyChanged. I think this means the data-bound value is not getting sent to the UserControl. (I think the constructor does not get called in the static case)
Solution: The problems were correctly identified by Arcturus and jpsstavares. First, I was overwriting the data binding when is set DataContext=this in the constructor of the control. This prevented the data bound value from getting set. I also had to name the control x:Name=root, and specify the Binding ElementName=root int the XAML. To get the TwoWay binding, I needed to set Mode=TwoWay in the caller. Here is the correct code:
<src:BlueTextBox BlueText="{Binding Path=MyString, Mode=TwoWay}}" /> <!--OK-->
Now the XAML in the UserControl:
<UserControl x:Class="Binding2.BlueTextBox" x:Name="root"...
<Grid>
<TextBox x:Name="myTextBox" Text="{Binding ElementName=root, Path=BlueText}" Foreground="Blue" Width="100" Height="26" />
</Grid>
Finally I removed the DataContext=this in the constructor of the UserControl.
public BlueTextBox()
{
InitializeComponent();
//DataContext = this; -- don't do this
}
Thanks everyone for the tremendous help!

You set the DataContext in the Control to itself, thus overwriting the DataContext when using this Control in other controls. Taking your binding as example in your situation:
<src:BlueTextBox BlueText="{Binding Path=MyString}" />
Once loaded and all the Datacontext is set, it will look for the path MyString in your BlueTextBox thing control due to you setting the DataContext to it. I guess this is not how you intended this to work ;).
Solution:
Change the text binding either one of the 2 bindings:
{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type src:BlueTextBox}}, Path=BlueText}
or
Name your control Root (or something like that)
<UserControl x:Name="Root"
{Binding ElementName=Root, Path=BlueText}
And remove the
DataContext = this;
from the constructor of your UserControl and it should work like a charm..

I think in this case you need to set the ElementName property in the binding. Something like this:
<UserControl x:Class="Binding2.BlueTextBox" x:Name="blueTextBox"...
<Grid>
<TextBox x:Name="myTextBox" Text="{Binding ElementName=blueTextBox, Path=BlueText}" Foreground="Blue" Width="100" Height="26" />
</Grid>

Possibly you need to add to your property FrameworkPropertyMetadata where specify FrameworkPropertyMetadataOptions.AffectsRender and AffectsMeasure.
FrameworkPropertyMetadataOptions enumeration MSDN article

I know this is an old topic but still.
Also mention the PropertyChangedCallback on the UIPropertyMetadata during registering your DP

Datacontext not available in DataGridTemplateColumn

I have the following grid:
<DataGrid
x:Name="CandiesDataGrid"
ItemsSource="{Binding Candies}"
SelectedItem="{Binding SelectedCandy}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding CandySelectedCommand}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
<DataGrid.Columns>
<DataGridTextColumn KeyboardNavigation.IsTabStop="False" IsReadOnly="True" Width="100" Header="{l:LocText Candy_Prop1}" Binding="{Binding CandyInfo.Name}"/>
<DataGridTemplateColumn >
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<CheckBox Name="IsConfirmed" Grid.Column="0"
Style="{StaticResource CandyCheckBox}"
IsChecked="{Binding IsConfirmed, Mode=TwoWay}"
Margin="-75 0 0 0"
Command="{Binding IsConfirmedCommand}">
</CheckBox>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>
My property uses the OnPropertyChanged. Not only it does not change the value of IsConfirmed but also does not executes the ICommand IsConfirmedCommand.
I searched on the internet and it seems DataGridTemplateColumn loses the ItemSource of the datagrid.
I did try to put RelativeSource in after the mode=TwoWay on my checkbox but it does not work.
Is there any way to have access to the ItemSource in my TemplateColumn?
EDIT:
//Properties
public ObservableCollection<Candy> Candies{ get; } = new ObservableCollection<Candy>();
public Candy SelectedCandy { get { return _selectedCandy; } set { SetProperty(ref _selectedCandy, value); } } //SetProperty acts as OnPropertyChanged
private Candy _selectedCandy;
//Constructor:
public CandyClass()
{
IsConfirmedCommand = new DelegateCommand(IsConfirmedCommand_Execute);
}
//Method
private void IsConfirmedCommand_Execute()
{
//Doing something
}

Inside your CellTemplate, the DataContext is the DataGrid row, whatever that may be (Candy in this case). So by default, that Candy instance will be the Source property of any Binding in that DataTemplate. That's where the binding will look for the property named in the Path (IsConfirmed and IsConfirmedCommand, in this case).
That's what you want: You've got more than one row in the grid, and the row is what you care about in a cell, usually. That or the field: But very often a cell template will want to look at more than one field, so they give you the whole row.
But in this case, you want to go back up and grab something off the parent viewmodel. Viewmodels have no natural parent/child hierarchy, though you could give them one if you wanted: Candy could have a Parent property that had reference to the viewmodel that owns the Candies collection. If you did, you could bind like this:
Command="{Binding Parent.IsConfirmed}"
But that's not common practice. I don't know if it's a particularly great idea or not.
One reason we don't need to do that is we can tell the binding to use a different source instead. UI elements do have a natural parent/child hierarchy, and bindings can navigate it. If you’re doing things right, your parent viewmodel will be the DataContext of something up there somewhere.
{Binding Path=DataContext.IsConfirmed,
RelativeSource={RelativeSource AncestorType=DataGrid}}
"Walk the UI tree upwards until you find a DataGrid. That's your source. Now, once you have a source, find the source object's DataContext property, if any. If it's got a DataContext, take the value of DataContext and look on that object for some property called IsConfirmed."
DataGrid has a DataContext property. Since your binding to Candies worked, we know that DataContext must be your class that has a Candies property. You assure me that class has IsConfirmed as well.
Hence:
<DataTemplate>
<CheckBox
Style="{StaticResource CandyCheckBox}"
IsChecked="{Binding DataContext.IsConfirmed,
RelativeSource={RelativeSource AncestorType=DataGrid}}"
Margin="-75 0 0 0"
Command="{Binding DataContext.IsConfirmedCommand,
RelativeSource={RelativeSource AncestorType=DataGrid}}"
/>
</DataTemplate>

Inherited DataContext - bindings not working

Following situation: I got a base class which provides a little framework for making modal dialogs with an adorner.
The base class has a property of type DataTemplate which contains the actual input scheme (all kinds of input are possible) as well as an object property which contains the mapping model (a model class to which the template binds it's input values).
Because I want to reuse the adorner, I made it have a ContentControl which anon has a ContentTemplate with the actual dialog design. The dialog's design contains a ContentControl whose Template is bound to the property in the adorner class. The DataContext of the adorner's ContentControl is set to itself, of course.
Now the embedded ContentControl (in the design) generates the DataTemplate and displays (in the current case) a TextBox. This TextBox now should be bound to the model. Therefore I reused the DataContext of the adorner design template for the actual input template. Here's how I've done it:
The adorner's ControlTemplate
<Border Grid.Row="0" Background="{DynamicResource InputAdornerHeaderBackground}" BorderThickness="0,0,0,1" CornerRadius="0">
<TextBlock HorizontalAlignment="Stretch" VerticalAlignment="Stretch" TextWrapping="Wrap" Text="{Binding Header}"
FontSize="{DynamicResource InputAdornerHeaderFontSize}" Foreground="{DynamicResource InputAdornerHeaderForeground}"
FontWeight="{DynamicResource InputAdornerHeaderFontWeight}" Margin="8" />
</Border>
<Border Grid.Row="1" BorderThickness="1,0,1,1" BorderBrush="{DynamicResource InputAdornerBorderBrush}" CornerRadius="0">
<ContentControl ContentTemplate="{Binding InputControlTemplate}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
</Border>
</Grid>
</ContentTemplate>
The actual input template (DataTemplate)
<DataTemplate x:Key="TextInputTemplate">
<Grid Background="Black" DataContext="{Binding DataContext.InputMapping, RelativeSource={RelativeSource AncestorType={x:Type ContentControl}}}">
<TextBox Text="{Binding Path=Text, Mode=OneWayToSource}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" BorderThickness="0"
adorners:InputAdorner.FocusElement="{Binding RelativeSource={RelativeSource Self}}" />
</Grid>
</DataTemplate>
Model class
public sealed class TextInputModel
{
public string Text { get; set; }
}
Adorner properties
public DataTemplate InputControlTemplate
{
get { return _inputControlTemplate; }
private set
{
if (Equals(value, _inputControlTemplate)) return;
_inputControlTemplate = value;
OnPropertyChanged();
}
}
public object InputMapping
{
get { return _inputMapping; }
private set
{
if (Equals(value, _inputMapping)) return;
_inputMapping = value;
OnPropertyChanged();
}
}
FYI: The model is being dynamically instantiated when the Adorner is being created. It does not get set twice. This must be some kind of binding issue.
The template shows correctly. I see and can input stuff into the textbox, but once I fetch the model all properties are default (""). It did work one or two times but somehow design changes have obviously made it disfunctional.
I don't get what is interfering here as from my point of view all should be set up correctly. I checked the context of the DataTemplate: It is the actual model class. Yet the textbox inputs do not update the property.
EDIT:
For some reason it seems that the attatched property is causing this issue. But why is it interfering? It does not override the DataContext, does it?

Binding one control to another's DataContext

I bind my wpf window to app layer class (WindowVM.cs) using DataContext in Window.xaml.cs constructor (DataContext = WindowVM). But, one control (btnAdd) I want to bind to Window.xaml.cs property. So in Window.xaml.cs constructor I add this.btnAdd.DataContext. This is Window.xaml.cs constructor and property to which I want bind Button btnAdd:
public Window()
{
InitializeComponent();
DataContext = WindowVM;
this.btnAdd.DataContext = this;
}
public RelayCommand Add
{
get
{
return _add == null ? _add= new RelayCommand(AddPP, CanAddPP) : _add;
}
set
{
OnPropertyChanged("Add");
}
}
Xaml looks like this (class PP is WindowVM property):
<TextBox Name="txtName" Text="{Binding PP.Name, ValidatesOnDataErrors=true, UpdateSourceTrigger=PropertyChanged}" />
<TextBox Name="txtSurname" Text="{Binding PP.Surname, ValidatesOnDataErrors=true, UpdateSourceTrigger=PropertyChanged}" />
<Button Command="{Binding Add}" Content="Add" ... />
And - everything works, but console output this:
BindingExpression path error: 'Add' property not found on 'object' ''WindowVM'...
In next calls there isn't any console output error for property Add.
Now I am a little bit confused because of this error. Is this error because of first DataContext (to WindowVM), because there isn't property Add, but with line this.btnAdd.DataContext property Add is found and it's the reason that it works?

Simply set the DataContext of the Button in the XAML using a RelativeSource:
<Button Command="{Binding Add}" Content="Add" DataContext="{Binding Add, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" />

I had this problem and I know this is an oldish post but I think this might help someone who stumbles on this in the future.
what I did was declare the viewmodels as resources
<Page.Resources>
<local:LocationListViewModel x:Key="LocationList" />
<local:LocationNewViewModel x:Key="NewLocation" />
<code:BinaryImageConverter x:Key="imgConverter" />
</Page.Resources>
then which ever control I wanted to be associated with said viewmodel I added this to their datacontext
<TabItem x:Name="tabSettingsLocations" x:Uid="tabSettingsLocations"
Header="Locations"
DataContext="{StaticResource ResourceKey=LocationList}">....
<TabItem x:Name="tbSettingsLocationsAdd" x:Uid="tbSettingsLocationsAdd"
Header="Add New"
DataContext="{StaticResource ResourceKey=NewLocation}">....
<Image x:Name="imgSettingsLocationMapNew" x:Uid="imgSettingsLocationMapNew"
Source="{Binding Map, Converter={StaticResource imgConverter},
Mode=TwoWay}"
DataContext="{StaticResource ResourceKey=NewLocation}" />
So in my example above I have Listview bound to the list viewmodel and I create a new single location for my new entry. You will notice that by creating it as a resource I can bind the tabitem and the image (which is not a child of the tab item) to the new location viewmodel.
My command for the addnew location is in the new location viewmodel.
<TabItem x:Name="tbSettingsLocationsAdd" x:Uid="tbSettingsLocationsAdd"
Header="Add New"
DataContext="{StaticResource ResourceKey=NewLocation}">....
<Button x:Name="btnSettingsLocationSaveAdd" x:Uid="btnSettingsLocationSaveAdd" Content="Submit" Margin="0,80,10,0"
VerticalAlignment="Top" Style="{DynamicResource ButtonStyle}" HorizontalAlignment="Right" Width="75"
Command="{Binding AddCommand}" />.....
Which is the child of the tabitem I bound to the new location viewmodel.
I hope that helps.

When you set the DataContext-Property, your Window resets the Bindings of it's child controls. Even the Binding of your button.
At this Point (before "button.DataContext = this" is evaluated) "Add" is searched in WindowVM. After this you set the Window class as buttons DC, and everything works fine.
To avoid the initial error, swap two lines from this
public Window()
{
InitializeComponent();
DataContext = WindowVM;
this.btnAdd.DataContext = this;
}
to this
public Window()
{
InitializeComponent();
this.btnAdd.DataContext = this;
DataContext = WindowVM;
}