I'm attempting to bind a string property to a TextBox's Text field in XAML. I am doing this in a UserControl. I've searched StackOverflow and the internet in general and found various related topics, some examples:
Binding objects defined in code-behind
WPF: simple TextBox data binding
I've followed the code in these examples as best as I can but the Input property does not appear to be binding to the TextBox. I've tried various different methods of setting up the DataContext, including from the code behind and it's still not working.
What is it that I'm missing, is this an issue because it's a UserControl?
The code in the SearchInputTextBox_TextChanged event is called but always outputs an empty string. If I put a Debug.WriteLine call in the Input set section nothing happens.
The XAML file:
<UserControl x:Class="DatabaseViewerApp.View.SearchBox"
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="70" d:DesignWidth="240"
x:Name="Control">
<Border Padding="5" Background="#303030">
<StackPanel>
<TextBlock Text="Search" Margin="0,0,0,0" FontSize="20px" Foreground="White"></TextBlock>
<TextBox Name="SearchInputTextBox" Text="{Binding ElementName=Control, Path=Input}" Margin="0,5" FontSize="15px" TextChanged="SearchInputTextBox_TextChanged"></TextBox>
</StackPanel>
</Border>
</UserControl>
The C# file:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace DatabaseViewerApp.View
{
/// <summary>
/// Interaction logic for SearchBox.xaml
/// </summary>
public partial class SearchBox : UserControl, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string input;
public string Input
{
get { return input; }
set
{
if (value != input)
{
input = value;
NotifyPropertyChanged("Input");
}
}
}
public void NotifyPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public SearchBox()
{
InitializeComponent();
}
private void SearchInputTextBox_TextChanged(object sender, TextChangedEventArgs e)
{
Debug.WriteLine(Input);
}
}
}
I think your problem is not that it isn't working... The issue is that you may not be testing it properly. Your code works for me in a new WPF solution. What you may be missing is that the Text binding gets updated when you leave the focus. In contrast, the TextChanged event gets fired as soon as the text is input into the text box.
So, whats happening is that when the TextChanged event is fired, the binding hasn't yet been updated. If you try putting a breakpoint in your property setter, then change some text in the text box, and move focus out of that control, you should see it get hit.
As an aside, there isn't much sense in binding your Text to a property in the code behind because the UI element can be accessed directly from there.
Try this:
<TextBox Name="SearchInputTextBox"
Text="{Binding RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType=UserControl},Path=Input}"
Margin="0,5" FontSize="15px" TextChanged="SearchInputTextBox_TextChanged">
</TextBox>
Related
This question already has answers here:
Why does WPF support binding to properties of an object, but not fields?
(2 answers)
Notify binding for static properties in static classes
(1 answer)
Closed 8 months ago.
I'm very new to C# and XAML. I'm trying to do a WPF project where there will be a good amount of data binding. Right now, I am able to do one way data binding without any problems, the issue I am facing is when I try to do two-way data binding.
This is the beginning of my Xaml file where I try to bind a text box to a static property in a static class:
<Window x:Class="interactive_fountain.MainWindow"
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:local="clr-namespace:interactive_fountain"
xmlns:include="clr-namespace:interactive_fountain.Include"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
<TextBox x:Name="ip_textBox" HorizontalAlignment="Left" Height="27" Margin="250,242,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="110" Text="{Binding Source={x:Static include:Communication.ipAddressServer}, Path=include:Communication.ipAddressServer, UpdateSourceTrigger=PropertyChanged}"/>
<Button Content="Button" HorizontalAlignment="Left" Margin="221,131,0,0" VerticalAlignment="Top" Height="47" Width="139" Click="Button_Click_1"/>
...
This is the beginning of the C# MainWindow Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Net;
using System.Net.Sockets;
using System.Diagnostics;
using interactive_fountain.Include;
namespace interactive_fountain
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click_1(object sender, RoutedEventArgs e)
{
Trace.WriteLine("ip: " + Communication.ipAddressServer);
}
...
And this is the beginning of the class I want to do data binding with:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net;
using System.Net.Sockets;
using System.Diagnostics;
namespace interactive_fountain.Include
{
public static class Communication
{
public static string ipAddressServer = "hello";
...
Whenever I try to do two-way data binding, the place holder "hello" doesn't appear anymore. When I write in the textBox and press the button, the output will always be ip: hello no matter what I write in the box. I have looked at a lot of threads regarding this issue but I did not find a solution that worked for me.
Does anyone know how I could make it work?
Thanks in advance!!
WPF data binding works on public properties only, your ipAddressServer is a static field (aka class variable) and not a property, so it won't be used. It's also failing at following proper naming conventions.
Your mess of a binding is the old style static binding, use {Binding Path=(w:Communication.IpAddressServer)} instead (after you fix #1, of course). w is the relevant XAML namespace definition.
Static properties don't have standard notifications for change, since static classes can't implement interfaces (for what I hope are obvious reasons). Instead WPF uses a convention-based approach of using a public static event PropertyChangedEventHandler StaticPropertyChanged and call that to notify changes. It's not clear if you want your property to be mutable, but you mentioned the change notification mechanism explicitly, so just throwing it out there.
I am a complete "weekend warrior" to programming so go gentle on me, please...
I want to achieve a simple task, which I had no problem with in plain C# (TextBox.Text = "Something";)
I have a textbox and a textblock in XAML, and I want to populate them from C#, simple as that - run the web app and pull the predefined strings from the C# code. I have been searching for 2 days now and can't find a straight answer. I don't want any triggers (buttons), just filling e.g. textbox on load with a C# string. A simple code example on both XAML and C# side would be greatly appreciated!
Cheers,
Sasa
Not sure if I'm understanding your question...
<!--xaml-->
<TextBox x:Name="txtMyTextBox"/>
// C#
// Window constructor
public MyWindow()
{
InitializeComponent();
txtMyTextBox.Text = "Something";
}
One simple way to achieve what you try to achieve (if I understood correctly), is to add the UI elements to your window and set a Name for each of them. This way, you can access them in your code-behind as seen below.
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
<Grid>
<TextBox Name="TextBox1" HorizontalAlignment="Left" Height="23" Margin="37,37,0,0" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="120"/>
<TextBlock Name="TextBlock1" HorizontalAlignment="Left" Margin="48,100,0,0" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top" Height="103" Width="239"/>
</Grid>
</Window>
While there are certainly more "refined" ways to achieve the same, once you named your UI elements in xaml, you can access them just as other object instances in your code-behind.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
TextBox1.Text = "Hello TextBox1!";
TextBlock1.Text = "Hello TextBlock1!";
}
}
}
My routed events are hitting the root UI element before the child element. Is this expected? How can I have the routed events hit the child element first?
Objective: If text is typed anywhere other than "custom textbox", put text in "default textbox"
Result: Window_PreviewTextInput is being hit before custom_PreviewTextInput, even if my cursor focus is on "Custom Textbox"
What should I do differently?
XAML
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" SizeToContent="WidthAndHeight"
PreviewTextInput="Window_PreviewTextInput"
>
<Grid Margin="100,100,100,100">
<StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="default" Width="100"/>
<TextBox x:Name="defaultTB" Width="300" Height="50"/>
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="custom" Width="100"/>
<TextBox x:Name="custom" PreviewTextInput="custom_PreviewTextInput" Width="300" Height="50"/>
</StackPanel>
</StackPanel>
</Grid>
</Window>
Code Behind:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfApplication2
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
//goal: if text is typed anywhere except custom textbox, put text in default textbox
private void Window_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
Keyboard.Focus(defaultTB);
}
//goal: if text is typed in custom TB, put text there, and end the event routing
private void custom_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
e.Handled = true;
}
}
}
Routed Event could be a bubbling or tunneling. You've a tunneling event behaviour.
From MSDN, UIElement.PreviewTextInput Event:
Routing strategy - Tunneling
The corresponding bubbling event is TextInput.
Routed Events Overview - Routing Strategies:
Bubbling: Event handlers on the event source are invoked. The routed
event then routes to successive parent elements until reaching the
element tree root. Most routed events use the bubbling routing
strategy. Bubbling routed events are generally used to report input or
state changes from distinct controls or other UI elements
Direct: Only the source element itself is given the opportunity to
invoke handlers in response. This is analogous to the "routing" that
Windows Forms uses for events. However, unlike a standard CLR event,
direct routed events support class handling (class handling is
explained in an upcoming section) and can be used by EventSetter and
EventTrigger.
Tunneling: Initially, event handlers at the element tree root are
invoked. The routed event then travels a route through successive
child elements along the route, towards the node element that is the
routed event source (the element that raised the routed event).
Tunneling routed events are often used or handled as part of the
compositing for a control, such that events from composite parts can
be deliberately suppressed or replaced by events that are specific to
the complete control. Input events provided in WPF often come
implemented as a tunneling/bubbling pair. Tunneling events are also
sometimes referred to as Preview events, because of a naming
convention that is used for the pairs.
I'm going round in circles here. I've kind of got the hang of XmlDataProvider bindings but the file I'm using seems too large to bind dynamically (50Mb doesn't work; 2Mb works). So instead I have the data loaded into classes using code generated from the XSD.
However, I can't get binding to CLR objects to work, due to my lack of knowledge. I'm using Visual Studio 2008 Pro, C# and .Net 3.5.
Here's the XAML file:
<Window x:Class="WpfObjectText.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfObjectText"
Title="Window1" Height="300" Width="300">
<Grid>
<Grid.Resources>
<ObjectDataProvider x:Key="simpleBinding" ObjectType="{x:Type local:ExampleClass}"/>
</Grid.Resources>
<StackPanel>
<TextBox Name="textBox1" Text="{Binding Path=simpleBinding}" />
</StackPanel>
</Grid>
</Window>
And the code behind:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfObjectText
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
public ExampleClass TestInstance = new ExampleClass("Hello, world!");
public Window1()
{
InitializeComponent();
}
}
public class ExampleClass
{
public string TestString { get; set; }
public ExampleClass(string initialText)
{
TestString = initialText;
}
}
}
I've deliberately kept it simple so I can take baby steps. All I want to do here is populate the textbox from an instance of ExampleClass, and have the TestString field updated if the textbox changes (ie bidirectional). I know I can set MethodName in the binding which works to a certain extent in ListBoxes but that doesn't seem to imply bidirectional to me. Coming from a Delphi7 Win32 programmer, this is alien territory for me!
Assistance appreciated.
These are the necessary changes:
<TextBox Name="textBox1" Text="{Binding Path=TestString}" />
and then in the constructor:
DataContext = TestInstance;
If my understanding of the question is correct, you don't need Grid.Resources section at all.
I have some controls where I set their Name property to unique names, but I am unable to access them in the matching C# code file.
I have tried:
this.ControlName
MainWindow.ControlName
ControlName
but it does "see" them.
How do I do this?
Also do I have to do something special for nested controls inside wrap panels, grid views, etc?
EDIT:
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Reflection;
namespace EditorWindow
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow ( )
{
}
}
}
<Window x:Class="EditorWindow.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Effects Editor">
<DockPanel>
<ListView x:Name="EffectsListView">
</ListView>
</DockPanel>
</Window>
For accessing any element in code behind you will need to set x:Name directive.
It tells the XAML parser to add a field representing the named element to the automatically generated portion of the Window class just like Winforms.
In a WPF application, there’s no requirement to name each and every element. You should name only those elements which you want to programatically interact with.
An example:
<TextBlock x:Name="tblText" Text="Stackoverflow rocks."></TextBlock>
EDIT:
I used the following code and I was able to access the list view:
namespace WpfApplicationUnleashed
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
EffectsListView.Width = 10;
}
}
}
<Window x:Class="WpfApplicationUnleashed.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
xmlns:local="clr-namespace:WpfApplicationUnleashed"
Title="Window1" >
<DockPanel>
<ListView x:Name="EffectsListView"></ListView>
</DockPanel>
</Window>
have you set their x:Name="ControlName" property in xaml?
Here is more information on x:Name directive.
For example:
<Button x:Name="Button1">Click Me</Button>