I want to do something like this diagram Data Binding Diagram.
If i update TextBox text Then update TextBlock text and Property and if i change Property Value then also update Textbox and textBlock text. Please tell me how can i do it using WPF ????
Thank`s For Help.
Im not sure if I understand right your question. Are the two Textboxes in the same view or in different?
Here a solution with 2 textboxes in the same view:
View (xaml):
<Window x:Class="Sandbox.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"
Name="mainWindow">
<StackPanel>
<TextBox Name="UpperTextBox" Text="{Binding ElementName=LowerTextBox, Path=Text,UpdateSourceTrigger=PropertyChanged}"/>
<TextBox Name="LowerTextBox" Text="{Binding MyValue, UpdateSourceTrigger=PropertyChanged}"/>
</StackPanel>
View-Codebehind (xaml.cs):
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new MyViewModel();
}
}
ViewModel:
public class MyViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
private string _myValue;
public string MyValue
{
get { return _myValue; }
set
{
_myValue = value;
OnPropertyChanged("MyValue");
}
}
}
Related
I have a problem with data binding. A test application that I have looks as follows:
There's a mainwindow:
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Controls="clr-namespace:WpfApplication2"
x:Name="main"
Title="MainWindow" >
<StackPanel >
<Button Content="Button" Click="Button_Click"/>
<Controls:UserControl1 />
</StackPanel>
</Window>
And a user control:
<UserControl x:Class="WpfApplication2.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"
mc:Ignorable="d"
x:Name="uc"
>
<Grid >
<TextBox Width="40" Text="{Binding ElementName=main,
Path=Status, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</UserControl>
I want to click the button on the main window to have the value of text box in user control updated:
The code of MainWindow file:
namespace WpfApplication2
{
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
private string _status;
public string Status
{
get { return _status; }
set
{
if (value != _status)
{
_status = value;
RaisePropertyChanged("Status");
}
}
}
private void Button_Click(object sender, RoutedEventArgs e)
{
if (Status == "one")
Status = "two";
else
Status = "one";
}
}
}
And the code of UserControl:
namespace WpfApplication2
{
public partial class UserControl1 : UserControl, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null) PropertyChanged(this, e: new PropertyChangedEventArgs(propertyName));
}
public UserControl1()
{
InitializeComponent();
}
}
}
I don't understand why doesn't it work, but the PropertyChanged is always null. The example is in the simplest form I can imagine...
You are trying to access the parent window using the ElementName binding, as far as I am aware, that is not possible. You can however use a relative source binding to get the parent window:
<TextBlock Text="{Binding RelativeSource={RelativeSource AncestorType=Window}, Path=Status}" ... />
Follow up edit:
Your child user control should look like this:
<UserControl
...
x:Name="usr">
<Grid>
<TextBlock Text="{Binding Message, ElementName=usr}"/>
</Grid>
</UserControl>
You will then need to create a dependency property called 'Message' (This is just an example, I'm not sure what you want to call this property).
public partial class YourUserControl: UserControl
{
public string Message
{
get { return (string)GetValue(MessageProperty); }
set { SetValue(MessageProperty, value); }
}
// Using a DependencyProperty as the backing store for Message. This enables animation, styling, binding, etc...
public static readonly DependencyProperty MessageProperty =
DependencyProperty.Register("Message", typeof(string), typeof(YourUserControl), new PropertyMetadata(""));
public UserControl1()
{
InitializeComponent();
}
}
Then, when you declare this in your parent user control, simply set the binding of the Message property to whatever property you need to bind to in your parent user control:
<YourNamespace:YourUserControl Message="{Binding PropertyName, ElementName=elementName}" />
I'm trying to do a simple binding but I'm having some problems. I have a text block and a button. The textblock is binded to a property called "word". When you press the button the value of word changes and I want to automacally update the text block. This is a classic example, please explain me what I'm doing wrong:
namespace WpfApplication5
{
public partial class MainWindow : Window, INotifyPropertyChanged
{
private string _word;
public string word
{
get { return _word; }
set
{
_word= value;
RaisePropertyChanged(word);
}
}
private void change_Click(object sender, RoutedEventArgs e)
{
word= "I've changed!";
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
}
And my XAML with the binding:
<Window x:Class="WpfApplication5.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">
<Grid>
<TextBlock HorizontalAlignment="Left" Margin="210,152,0,0" TextWrapping="Wrap" Text="{Binding word}" VerticalAlignment="Top"/>
<Button x:Name="change" Content="Change" HorizontalAlignment="Left" Margin="189,235,0,0" VerticalAlignment="Top" Width="75" Click="change_Click"/>
</Grid>
</Window>
You are raising a PropertyChanged event for a property named I've changed!, because you pass the value of the property word to RaisePropertyChanged. You need to pass the name of the property instead:
RaisePropertyChanged("word");
This answer assumes that the data context is set correctly. If not, you need to fix that too:
DataContext = this;
I'm trying to validate the text in a textbox when a key is pressed. Here's the shortest code sample that shows what I'm trying to do:
<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">
<Grid>
<TextBox FontSize="15" HorizontalAlignment="Left" Name="txtEmail" VerticalAlignment="Top" Width="135"
Text="{Binding ValidationRules.EmailAddress, ValidatesOnExceptions=True, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</Window>
"ValidationRules" class:
class ValidationRules
{
string email = "";
public string EmailAddress
{
get
{
return email;
}
set
{
Console.WriteLine("Setting!");
//Only check if there is any text for now...
if (String.IsNullOrWhiteSpace(value))
{
throw new Exception();
}
email = value;
}
}
}
When I start typing in the textbox, I don't get "Setting" as console output, even though I'm using UpdateSourceTrigger=PropertyChanged. I've done my research but all the examples I could find are long winding and confusing. I would also appreciate it if you could point out any other mistakes I have in validation, but try to explain in simple terms if possible because I'm new to WPF.
It must be an issue on where you are setting your DataContext.
This example seems to work fine:
Code:
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
ValidationRules = new ValidationRules();
}
private ValidationRules _validation;
public ValidationRules ValidationRules
{
get { return _validation; }
set { _validation = value; NotifyPropertyChanged("ValidationRules"); }
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
public class ValidationRules : INotifyPropertyChanged
{
string email = "";
public string EmailAddress
{
get
{
return email;
}
set
{
Console.WriteLine("Setting!");
//Only check if there is any text for now...
if (String.IsNullOrWhiteSpace(value))
{
throw new Exception();
}
email = value;
NotifyPropertyChanged("EmailAddress");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
Xaml
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="WpfApplication1.MainWindow"
Title="MainWindow" Height="125.078" Width="236.441" x:Name="UI" >
<Grid DataContext="{Binding ElementName=UI}">
<TextBox FontSize="15" HorizontalAlignment="Left" Name="txtEmail" VerticalAlignment="Top" Width="135"
Text="{Binding ValidationRules.EmailAddress, ValidatesOnExceptions=True, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</Window>
I am new to WPF programming, so forgive me if this is a simple issue.
I have my Mainwindow.xaml set up like so:
<Window x:Class="GNMAwpf.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:GNMAwpf"
Title="Uploader"
Height="353" Width="342" ResizeMode="NoResize" WindowStartupLocation="CenterScreen">
<Window.DataContext>
<local:GinniNet x:Name="g" />
</Window.DataContext>
Further down I have a textblock:
<TextBlock Text="{Binding Path=StatusText}" Grid.ColumnSpan="2" MinWidth="150"></TextBlock>
In my class i have :
class GinniNet : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string _statusMessage;
public string StatusMessage
{
get
{
return _statusMessage;
}
set
{
_statusMessage = value;
OnPropertyChanged("StatusMessage");
}
}
public GinniNet()
{
StatusMessage = "Ready";
}
private void OnPropertyChanged(string property)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
When I change StatusMessage The textblock does not update ever. Where am i making my mistake?
Binding is incorrect -
<TextBlock Text="{Binding Path=StatusText}"/>
It should be -
<TextBlock Text="{Binding Path=StatusMessage}"
Currently, within a real-world application development, I am struggling with the consumption of a custom UserControl in the MVVM pattern.
In my application, there is a DataGrid where the user can select an entry. The DataGrid's SelectedItem is TwoWay-bound to a field of the ViewModel set as DataContext. When the user selects an entry, the field is properly updated (tested). In the Page where holds the DataGrid, the field is bound through XAML to a DependencyProperty of a custom UserControl devised in the MVVM pattern : it bares its own ViewModel which is set as DataContext. The trouble is that the UserControl's DependencyProperty is not updated when the field changes even though the INotifyPropertyChanged interface is correctly implemented (see the comparison with a traditional control in the next minimal working example).
This example is constituted of a Label and bares ViewModelUserControl as a DataContext, UserControl1is consumed by the MainWindow and the binding is compared to that of a Label.
The file MainWindow.xaml:
<Window x:Class="UserControlWithinUserControlDataContext.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Local="clr-namespace:UserControlWithinUserControlDataContext"
Title="MainWindow"
Height="350" Width="525"
>
<StackPanel Orientation="Horizontal"
>
<ListBox SelectedItem="{Binding Text, Mode=TwoWay}"
x:Name="listbox"
Height="150"
>
</ListBox>
<Local:UserControl1 Text="{Binding Text, Mode=OneWay}"
Height="50" Width="150"
/>
<Label Content="{Binding Text, Mode=OneWay}"
/>
</StackPanel>
</Window>
The code-behind MainWindow.xaml.cs:
public partial class MainWindow : Window
{
public ViewModelWindow view_model_window
{
get { return _view_model; }
}
private ViewModelWindow _view_model = new ViewModelWindow();
public MainWindow()
{
InitializeComponent();
DataContext = view_model_window;
IList<String> list = new List<String>();
list.Add("A");
list.Add("B");
list.Add("C");
listbox.ItemsSource = list;
}
}
The ViewModel of the MainWindow, the file ViewModelWindow.cs :
public class ViewModelWindow : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public String Text
{
get { return text; }
set
{
if (text != value)
{
text = value;
NotifyPropertyChanged("Text");
}
}
}
private String text = "Bli";
}
The file UserControl1.xaml:
<UserControl x:Class="UserControlWithinUserControlDataContext.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"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<Grid>
<Label Content="{Binding Text}"
Background="Magenta"
HorizontalAlignment="Stretch"
/>
</Grid>
</UserControl>
The code-behind file UserControl1.xaml.cs:
public partial class UserControl1 : UserControl
{
public ViewModelUserControl view_model_usercontrol
{
get { return _view_model; }
}
private ViewModelUserControl _view_model = new ViewModelUserControl();
public String Text
{
get { return (String)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(String), typeof(UserControl1),
new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.AffectsRender,
new PropertyChangedCallback(TextPropertyChangedCallback)));
private static void TextPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
UserControl1 user_control = d as UserControl1;
if(user_control != null)
{
user_control.view_model_usercontrol.Text = user_control.Text;
}
}
public UserControl1()
{
InitializeComponent();
DataContext = view_model_usercontrol;
}
}
The ViewModel of UserControl1, the file ViewModelUserControl.cs:
public class ViewModelUserControl : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public String Text
{
get { return text; }
set
{
if (text != value)
{
text = value;
NotifyPropertyChanged("Text");
}
}
}
private String text = "";
}
As you can see when executing this code, the MainWindow's Label gets updated while the UserControl1's Label doesn't.
What am I doing wrong? Is there a way to makes this works?
Many thanks in advance for any clue.
first you do not need to add anything in the UserControl just the XAML. Remove all the code of the UserControl and try.
Let's explain why:
Content="{Binding Text}" you set this in the usercontrol xaml, it's binded to the ViewModelWindow. and that works. and remove in
<Local:UserControl1 => Text="{Binding Text, Mode=OneWay}"
Ok, but it is correct to define a property in the user control in case of other situation?, that's right, in order to do that:
<UserControl x:Name="UserControlInstance"...>
<Label Content="{Binding Text, ElementName=UserControlInstance}" ...>
Where in this case Text is the dependency property and not the datacontext property.
Try the first option, and then the second defining just a Dependency Property and in this case bind the dependency property as you did.
And a tip, if a dependency property is in the visual element tree like in your case you do not need to call the callback.
Thank you Juan for your answer, here is the solution for conceiving the UserControl in the MVVM pattern:
I gave the name root to the Grid of UserControl1 and set its DataContext:
root.DataContext = view_model_usercontrol;
instead of:
DataContext = view_model_usercontrol;
Everything works fine.
Happy ending :)