Develop Reference

WPF Set a TextBox property in code-behind

Hi I want to set the Text property of a Textbox by code behind. At the moment I do using XAML:
<TextBox x:Name="txtFilter" Text="{Binding FiltroFunzioni, Mode=OneWayToSource}" Grid.Row="0" />
As test I did this:
Binding b = new Binding();
b.Mode = BindingMode.OneWayToSource;
b.Path = new PropertyPath("Text"); //??
b.Source = PageViewModel.FiltroFunzioni;
BindingOperations.SetBinding(txtFilter, TextBlock.TextProperty, b);
The variable "FiltroFunzioni" is a string defined as property:
private string _filtroFunzioni = "";
public string FiltroFunzioni
{
get { return _filtroFunzioni; }
set
{
_filtroFunzioni = value;
RaisePropertyChanged("FiltroFunzioni");
_functionsView.Refresh();
}
}
Basically I dunno what kind of value should I set as PropertyPath. Any ideas?

You don't need the PropertyPath here. If you just remove it, your binding should work.
That being said, you should bind in XAML wherever possible.
If your issue is that changes to FiltroFunzioni don't update your textbox, that's because your binding is specifically declared as OneWayToSource: that means that changing the UI changes the source, but changing the source doesn't change the UI. If that isn't what you want, set the Mode to something else, like "TwoWay" - then changes to the source change the UI, AND changes to the UI change the source.
EDIT:
If you really want to bind from your ViewModel instead of just using XAML, TwoWay binding requires utilizing the Path for some reason, when binding through C#. Either of the following solutions work:
b.Source = FiltroFunzioni;
b.Path = new PropertyPath(".");
b.Source = this;
b.Path = new PropertyPath("FiltroFunzioni");
Note that with TwoWay binding you have to either initialize your FiltroFunzioni by setting the TextBox.Text property in your XAML, or setting FiltroFunzioni after the binding was initialized. Otherwise, WPF will immediately override it from the (by default empty) Text in your TextBox.

Binding on a nested property without using XAML

How to make a binding on a nested target property, like Shape.Stroke.Color in WPF without using XAML ?
For a simple property I'm using a code looking like this :
var binding = new Binding("mySourceProperty");
binding.Source = mySourceObject;
myTargetObject.SetBinding(myTargetProperty, binding);
Where myTargetProperty can be, for example, Shape.StrokeProperty.
But now, how can I do the same thing on the ColorProperty of the Stroke of a Shape ?

Provided that the Shape's Stroke property holds a SolidColorBrush, you can use the static BindingOperations.SetBinding method:
var shape = new Path(); // or whatever
var binding = new Binding { Source = Colors.Red }; // or whatever
BindingOperations.SetBinding(shape.Stroke, SolidColorBrush.ColorProperty, binding);

Creating Binding from Code-Behind not working C# XAML

I have the following code that creates a binding in code-behind. However, it does not seem to work (when the text in PageMarginTextBox is changed, nothing happens, and when the app is loaded, the Padding of newPage is not set to the text of PageMarginTextBox). To make matters worse, no Exceptions are thrown at all. All elements have been defined earlier on.
Binding pageMarginBinding = new Binding
{
Source = PageMarginTextBox,
Path = new PropertyPath("Text"),
};
newPage.SetBinding(ContentControl.PaddingProperty, pageMarginBinding);
//PageMarginTextBox.Text determines the Padding of newPage
How can I fix this? Any solutions would be appreciated. Thanks!

You are trying to Bind PaddingProperty to text. Padding property is of type Thickness and Text property is String.
I am not sure whether you want to bind padding / text, just giving you an idea if you want to bind the Padding.
Binding pageMarginBinding = new Binding
{
Source = PageMarginTextBox,
Path = new PropertyPath("Padding"),
};
newPage.SetBinding(ContentControl.PaddingProperty, pageMarginBinding);
Your problem is because you are trying to assign a string to a Thickness. In XAML the compiler internally translates the string "0,0,2,2" to Thickness object. But in code behind you have to write the code for the conversion yourself.
ThicknessConverter myThicknessConverter = new ThicknessConverter();
PageThickness= (Thickness)myThicknessConverter.ConvertFromString(PageMarginTextBox.Text);
Then you have to bind this to your control. Again this is only half the solution. You need to wire this up with the Binding.
private Thickness _pageThickness;
public Thickness PageThickness
{
get
{
return _pageThickness;
}
set
{
_pageThickness = value;
NotifyPropertyChanged("PageThickness");
}
Then you probably can bind it in XAML

How to programmatically bind Visibility on a button to INotifyPropertyChanged boolean property in C#?

Here's what I got to so far:
System.Windows.Data.Binding binding = new System.Windows.Data.Binding("MyProperty");
binding.Mode = System.Windows.Data.BindingMode.TwoWay;
binding.Converter = new System.Windows.Controls.BooleanToVisibilityConverter();
binding.Source = mySourceObject;
this.SetBinding(this.myButton.Visibility, binding);
but visibility is not a dependency property, so how can I do this?

You should be able to do
Button.VisibilityProperty
instead of
this.myButton.Visibility
http://msdn.microsoft.com/en-us/library/system.windows.uielement.visibilityproperty.aspx

You need to pass in the static Visibility dependency property itself (which Button inherits from UIElement), not the value of the property on the button instance, e.g.:
myButton.SetBinding(UIElement.VisibilityProperty, binding);

Attaching DataTriggers at runtime

Is it possible to attach datatriggers to a style at runtime? I've been through my (non-working) code a few times now and can't seem to find where I've gone wrong.
Here's the method I use to attach the style and trigger:
private void AttachVisibilityTrigger(Control ctrl)
{
Style stl = new System.Windows.Style();
DataTrigger dt = new DataTrigger();
PropertyInfo pi = _entity.GetType().GetProperty(this.SecondaryOptions[ctrl.Name]);
Type controlType = this.GetControlTypeForProperty(ref dt, pi); //gets the control type based on the property name and then sets the value for the DataTrigger for which I want the visibility to be hidden
Binding b = this.GetVisibilityBindingByControlType(controlType); //returns a new Binding with the appropriate Path set that corresponds to the bound property value (e.g IsChecked for CheckBoxes, Text for TextBoxes, SelectedValue for Comboboxes, etc)
b.ElementName = this.SecondaryOptions[ctrl.Name];
dt.Binding = b;
dt.Setters.Add(new Setter(Control.VisibilityProperty, System.Windows.Visibility.Hidden));
stl.Triggers.Add(dt);
ctrl.Style = stl;
}

I'm pretty sure the binding is just broken, i created similar styles in code and they work.
Especially this line looks quite suspicious:
b.ElementName = this.SecondaryOptions[ctrl.Name];
(If you want to bind to the control itself use RelativeSource instead.)
Have you checked the Output window of VisualStudio for binding errors?