Training
Module
Create a UI that uses data binding in .NET MAUI. - Training
Create a UI with data binding. Your UI automatically updates based on the latest data, while the data updates in response to changes in the UI.
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The EnumToBoolConverter
is a one way converter that allows you to convert an Enum
to a corresponding bool
based on whether it is equal to a set of supplied enum values. It is useful when binding a collection of values representing an enumeration type to a boolean control property like the IsVisible
property.
The Convert
method returns the supplied value
converted to an bool
based on whether the value
is equal to any of the defined TrueValues
or the supplied CommandParameter
.
The ConvertBack
method is not supported.
Note
Note that the 'true' value to compare to can be supplied in the following ways:
TrueValue
property on the converter.ConverterParameter
in the converter binding,Note that the TrueValues
property will take precedence over the ConverterParameter
option.
The following properties are implemented in the base class, public abstract class BaseConverter
:
Property | Description |
---|---|
DefaultConvertReturnValue |
Default value to return when IValueConverter.Convert(object?, Type, object?, CultureInfo?) throws an Exception . This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true . |
DefaultConvertBackReturnValue |
Default value to return when IValueConverter.ConvertBack(object?, Type, object?, CultureInfo?) throws an Exception . This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true . |
The following properties are implemented in the public interface ICommunityToolkitValueConverter
:
Property | Type | Description |
---|---|---|
DefaultConvertReturnValue |
object? |
Default value to return when IValueConverter.Convert(object?, Type, object?, CultureInfo?) throws an Exception . This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true . |
DefaultConvertBackReturnValue |
object? |
Default value to return when IValueConverter.ConvertBack(object?, Type, object?, CultureInfo?) throws an Exception . This value is used when CommunityToolkit.Maui.Options.ShouldSuppressExceptionsInConverters is set to true . |
Each of the following examples make use of the following enum definition:
namespace MyLittleApp;
public enum MyDevicePlatform
{
Android,
iOS,
macOS,
Tizen,
Windows
}
In order to use the toolkit in XAML the following xmlns
needs to be added into your page or view:
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
Therefore the following:
<ContentPage
x:Class="CommunityToolkit.Maui.Sample.Pages.MyPage"
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">
</ContentPage>
Would be modified to include the xmlns
as follows:
<ContentPage
x:Class="CommunityToolkit.Maui.Sample.Pages.MyPage"
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit">
</ContentPage>
The EnumToBoolConverter
can be used as follows in XAML:
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
xmlns:mylittleapp="clr-namespace:MyLittleApp"
x:Class="MyLittleApp.MainPage">
<ContentPage.Resources>
<ResourceDictionary>
<toolkit:EnumToBoolConverter x:Key="MobileConverter">
<toolkit:EnumToBoolConverter.TrueValues>
<mylittleapp:MyDevicePlatform>Android</mylittleapp:MyDevicePlatform>
<mylittleapp:MyDevicePlatform>iOS</mylittleapp:MyDevicePlatform>
</toolkit:EnumToBoolConverter.TrueValues>
</toolkit:EnumToBoolConverter>
</ResourceDictionary>
</ContentPage.Resources>
<VerticalStackLayout>
<Picker ItemsSource="{Binding Platforms}"
SelectedItem="{Binding SelectedPlatform}" />
<Label IsVisible="{Binding SelectedPlatform, Converter={StaticResource MobileConverter}}"
Text="I am visible when the Picker value is Android or iOS."/>
</VerticalStackLayout>
</ContentPage>
It is also possible to pass the converter parameter:
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
x:Class="MyLittleApp.MainPage">
<ContentPage.Resources>
<ResourceDictionary>
<toolkit:EnumToBoolConverter x:Key="PlatformConverter" />
</ResourceDictionary>
</ContentPage.Resources>
<VerticalStackLayout>
<Picker ItemsSource="{Binding Platforms}"
SelectedItem="{Binding SelectedPlatform}" />
<Label IsVisible="{Binding SelectedPlatform, Converter={StaticResource PlatformConverter}, ConverterParameter={x:Static vm:MyDevicePlatform.Tizen}}"
Text="I am visible when the Picker value is Tizen."/>
</VerticalStackLayout>
</ContentPage>
The EnumToBoolConverter
can be used as follows in C#:
class EnumToBoolConverterPage : ContentPage
{
public EnumToBoolConverterPage()
{
var picker = new Picker();
picker.SetBinding(Picker.ItemsSourceProperty, static (ViewModel vm) => vm.Platforms);
picker.SetBinding(Picker.SelectedItemProperty, static (ViewModel vm) => vm.SelectedPlatform);
var label = new Label
{
Text = "I am visible when the Picker value is Tizen."
};
label.SetBinding(
Label.IsVisibleProperty,
new Binding(
static (ViewModel vm) => vm.SelectedPlatform,
converter: new EnumToBoolConverter(),
converterParameter: MyDevicePlatform.Tizen));
Content = new VerticalStackLayout
{
Children = { picker, label }
};
}
}
Our CommunityToolkit.Maui.Markup
package provides a much more concise way to use this converter in C#.
using CommunityToolkit.Maui.Markup;
class EnumToBoolConverterPage : ContentPage
{
public EnumToBoolConverterPage()
{
Content = new VerticalStackLayout
{
Children =
{
new Picker()
.Bind(
Picker.ItemsSourceProperty,
static (ViewModel vm) => vm.Platforms)
.Bind(
Picker.SelectedItemProperty,
static (ViewModel vm) => vm.SelectedPlatform),
new Label()
.Text("I am visible when the Picker value is Tizen.")
.Bind(
Label.IsVisibleProperty,
static (ViewModel vm) => vm.SelectedPlatform,
converter: new EnumToBoolConverter(),
converterParameter: MyDevicePlatform.Tizen)
}
};
}
}
Property | Type | Description |
---|---|---|
TrueValues | IList<Enum> |
Enum values, that converts to true (optional). |
You can find an example of this converter in action in the .NET MAUI Community Toolkit Sample Application.
You can find the source code for EnumToBoolConverter
over on the .NET MAUI Community Toolkit GitHub repository.
.NET MAUI Community Toolkit feedback
.NET MAUI Community Toolkit is an open source project. Select a link to provide feedback:
Training
Module
Create a UI that uses data binding in .NET MAUI. - Training
Create a UI with data binding. Your UI automatically updates based on the latest data, while the data updates in response to changes in the UI.