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.

WPF Programmatically add DataGridTextColumn with DataTrigger

I have a DataGrid that is made of dynamically by the user. That means each time it runs the columns could and will be very different. Each column is programmatically added for that reason. I need to add some DataTriggers to it so figured this would work:
Style style = new Style();
style.TargetType = typeof(DataGridTextColumn);
DataTrigger tg = new DataTrigger()
{
Binding = new Binding(value),
Value = "bad data"
};
tg.Setters.Add(new Setter()
{
Property = UIElement.VisibilityProperty,
Value = Visibility.Hidden
});
While this gives no errors in the IDE when run it crashes and gives me
'DataGridTextColumn' type must derive from FrameworkElement or FrameworkContentElement.
What is the correct way of adding a DataTrigger to a DataGridTextColumn Programmatically

You need to use typeof(DataGridCell). The trigger should be applied to the Cell itself, not the Column.

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

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?

WPF RichTextBox - Selected Block?

I am experimenting with the WPF RichTextBox and notice that I can itterate through the blocks that make up its document by looping through RichTextBox.Document.Blocks.
What is the best way to get the Block that surrounds the caret?
I can get the CaretPosition and the ElementStart and ElementEnd properties of each block but can't see how to compare them because the actual character offsets are not exposed unless I am missing something obvious.

var curCaret = richTextBox1.CaretPosition;
var curBlock = richTextBox1.Document.Blocks.Where(x => x.ContentStart.CompareTo(curCaret) == -1 && x.ContentEnd.CompareTo(curCaret) == 1).FirstOrDefault();

Answer above probably works in WPF RTB but not in Silverlight 4.0. Most likely SL doesn't allow access to the Document protion of the RTB. So you have to do it via Reflection....
Something like this:
Set up a TextSelectionChanged Event Handler
Grab the TextSelection Pointer and find the Start TextPointer
Grab the TextSelection.Start.Parent item
Find out if it is of type paragraph
Parse the Paragraph.Inlines
Look for type of InlineUIContainer you need a cast it accordingly.

In Silverlight5 get the properties to be used to update a toolbar:
private void rtb_SelectionChanged(object sender, RoutedEventArgs e)
{
TextSelection ts = rtb.Selection;
object property;
property = ts.GetPropertyValue(Run.FontWeightProperty);
System.Windows.FontWeight fontWeight = property is System.Windows.FontWeight ? (FontWeight)property : FontWeights.Normal;
property = ts.GetPropertyValue(Run.FontStyleProperty);
System.Windows.FontStyle fontStyle = property is System.Windows.FontStyle ? (FontStyle)property : FontStyles.Normal;
TextDecorationCollection textDecorations = ts.GetPropertyValue(Run.TextDecorationsProperty) as TextDecorationCollection;
bool isUnderlined = textDecorations != null;
double? fontSize = ts.GetPropertyValue(Run.FontSizeProperty) as double?;
SolidColorBrush foreground = ts.GetPropertyValue(Run.ForegroundProperty) as SolidColorBrush;
Color foregroundColor = foreground != null ? foreground.Color : Colors.Black;
System.Diagnostics.Debug.WriteLine("fontweight:{0}, fontStyle:{1}, Underline:{2}, size:{3}, color:{4}",
fontWeight,
fontStyle,
isUnderlined,
fontSize,
foregroundColor);
if (fontSize.HasValue)
SetToolbarFontSize(fontSize.Value);
SetToolbarFontColor(foregroundColor);
}

Paragraph currentParagraph = richTextBox1.CaretPosition.Paragraph;
This code will return a Paragaph object and instead of a Block object but because the blocks in a RichTextBox are typically paragraphs this will not pose any problem.
MS Docs:
The Blocks property is the content property of RichTextBox. It is a collection of Paragraph elements.