IsStringNotNullOrWhiteSpaceConverter

The IsStringNotNullOrWhiteSpaceConverter is a one way converter that returns a bool indicating whether the binding value is not null, not an string.Empty and does not contain whitespace characters only.

The Convert method returns true when the binding value is not null, not an string.Empty and does not contain whitespace characters only.

The ConvertBack method is not supported. For the opposite behavior see the IsStringNullOrWhitespaceConverter.

BaseConverter Properties

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.

ICommunityToolkitValueConverter Properties

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.

Syntax

XAML

Including the XAML namespace

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>

Using the IsStringNotNullOrWhitespaceConverter

The IsStringNotNullOrWhiteSpaceConverter 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"
             x:Class="CommunityToolkit.Maui.Sample.Pages.Converters.IsStringNotNullOrWhiteSpaceConverterPage">

    <ContentPage.Resources>
        <ResourceDictionary>
            <toolkit:IsStringNotNullOrWhiteSpaceConverter x:Key="IsStringNotNullOrWhiteSpaceConverter" />
        </ResourceDictionary>
    </ContentPage.Resources>

    <Label Text="A value has been entered"
           IsVisible="{Binding MyValue, Converter={StaticResource IsStringNotNullOrWhiteSpaceConverter}}" />

</ContentPage>

C#

The IsStringNotNullOrWhiteSpaceConverter can be used as follows in C#:

class IsStringNotNullOrWhiteSpaceConverterPage : ContentPage
{
    public IsStringNotNullOrWhiteSpaceConverterPage()
    {
        var label = new Label { Text = "A value has been entered" };

		label.SetBinding(
			Label.IsVisibleProperty,
			new Binding(
				nameof(ViewModels.MyValue),
				converter: new IsStringNotNullOrWhiteSpaceConverter()));

		Content = label;
    }
}

C# Markup

Our CommunityToolkit.Maui.Markup package provides a much more concise way to use this converter in C#.

using CommunityToolkit.Maui.Markup;

class IsStringNotNullOrWhiteSpaceConverterPage : ContentPage
{
    public IsStringNotNullOrWhiteSpaceConverterPage()
    {
        Content = new Label { Text = "A value has been entered" }
            .Bind(
                Label.IsVisibleProperty,
                static (ViewModel vm) => vm.MyValue,
                converter: new IsStringNotNullOrWhiteSpaceConverter());
    }
}

Examples

You can find an example of this converter in action in the .NET MAUI Community Toolkit Sample Application.

API

You can find the source code for IsStringNotNullOrWhiteSpaceConverter over on the .NET MAUI Community Toolkit GitHub repository.