I've searched this question a lot. But, it seems no solutions are working for me. I don't get any errors but I've added a breakpoint to my IValueConverter. The breakpoint does not ever get triggered. Why is it not using my converter? All I want to do is use view model strategy for visibility binding of a UI element (in this case a checkbox). Any help is appreciated.
IValueConverter:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Data;
namespace Test_Tool.Common
{
public class BooleanToVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, string language) => (bool)value ^ (parameter as string ?? string.Empty).Equals("Reverse") ? Visibility.Visible : Visibility.Collapsed;
public object ConvertBack(object value, Type targetType, object parameter, string language) => (Visibility)value == Visibility.Visible ^ (parameter as string ?? string.Empty).Equals("Reverse");
}
}
XAML:
<Page
x:Class="Test_Tool.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Test_Tool"
xmlns:converter="using:Test_Tool.Common"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Grid.Resources>
<converter:BooleanToVisibilityConverter x:Key="cvt" />
</Grid.Resources>
<Pivot x:Name="rootPivot" Title="Test Tool" >
<PivotItem Header="Test Selection">
<StackPanel>
<CheckBox x:Name="dppCheckBox" Content="DPP" Margin="5,8,5,5" Visibility="{Binding IsDirect, Converter={StaticResource cvt}}" />
</StackPanel>
</PivotItem>
</Pivot>
</Grid>
</Page>
ViewModel:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
namespace Test_Tool.ViewModels
{
public class MainPageViewModel : INotifyPropertyChanged
{
//Localized private vars
private bool _isDirect;
//Public vars for bindings
public bool IsDirect
{
get
{
return _isDirect;
}
set
{
_isDirect = value;
OnPropertyChanged();
}
}
public MainPageViewModel()
{
//Any Initialization
IsDirect = false;
}
public event PropertyChangedEventHandler PropertyChanged;
void OnPropertyChanged([CallerMemberName]string propertyName = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
MainPage:
using DM_API_Test_Tool.ViewModels;
using Windows.UI.Xaml.Controls;
// The Blank Page item template is documented at https://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409
namespace Test_Tool
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class MainPage : Page
{
public MainPageViewModel ViewModel { get; set; }
public MainPage()
{
this.InitializeComponent();
this.ViewModel = new MainPageViewModel();
}
}
}
Try this
namespace Test_Tool.ViewModels
{
public class MainPageViewModel : INotifyPropertyChanged
{
private bool _isDirect = false;
public bool IsDirect
{
get
{
return _isDirect;
}
set
{
set { SetField(ref _isDirect, value, "isDirect"); }
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
protected bool SetField<T>(ref T field, T value, string propertyName)
{
if (EqualityComparer<T>.Default.Equals(field, value)) return false;
field = value;
OnPropertyChanged(propertyName);
return true;
}
}
}
this should work now.
However I prefer the BindableBase
method more (save the content below in a new class and call it something like BindableBase.cs
)
using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace Mvvm
{
public abstract class BindableBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected bool SetProperty<T>(ref T storage, T value, [CallerMemberName] String propertyName = null)
{
if (object.Equals(storage, value)) return false;
storage = value;
this.OnPropertyChanged(propertyName);
return true;
}
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var eventHandler = this.PropertyChanged;
if (eventHandler != null)
{
eventHandler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
and then your ViewModel
would be reduced to
using Mvvm;
namespace Test_Tool
{
public class MainPageViewModel : BindableBase
{
private bool _isDirect = false;
public bool IsDirect
{
get { return _isDirect; }
set { SetProperty(ref _isDirect, value); }
}
}
}
and one last thing: In your MainPage.xaml
you want to bind to rootPivot
, so you call
rootPivot.DataContext = null;
rootPivot.DataContext = new MainPageViewModel();
or something like that.
You can also try using external convertor library. I found this nuget package: click here
This library is very simple to use, first install the nuget package and insert:
<Window x:Class="WPFUI.Views.MainWindow"
...
xmlns:convertor="clr-namespace:suren37.convertor;assembly=suren37.convertor"
...>
as namespace at the top of the view and you can now bind a boolean value to the visibility as
<CheckBox Grid.Row="1" IsChecked="{Binding IsVisibile}" Grid.Column="1" Margin="8 0" />
<TextBlock Grid.Row="1" Text="This text becomes visible on checked"
Visibility="{Binding IsVisibile, Converter={convertor:BoolToVisibilityConverter}}"
Grid.Column="2" TextWrapping="WrapWithOverflow"/>
To check out the working sample visit the github page, here .
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.