is-string-not-null-or-whitespace-converter.md

title	author	description	ms.date
IsStringNotNullOrWhiteSpaceConverter - .NET MAUI Community Toolkit	bijington	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.	03/30/2022

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.

[!INCLUDE common converter properties]

Syntax

XAML

Including the XAML namespace

[!INCLUDE XAML usage guidance]

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.