CharactersValidationBehaviorPage.xaml

<?xml version="1.0" encoding="UTF-8"?>

<pages:BasePage x:Class="CommunityToolkit.Maui.Sample.Pages.Behaviors.CharactersValidationBehaviorPage"
                xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                xmlns:mct="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
                xmlns:pages="clr-namespace:CommunityToolkit.Maui.Sample.Pages"
                xmlns:vm="clr-namespace:CommunityToolkit.Maui.Sample.ViewModels.Behaviors"
                x:TypeArguments="vm:CharactersValidationBehaviorViewModel"
                x:DataType="vm:CharactersValidationBehaviorViewModel">

    <pages:BasePage.Resources>
        <Style x:Key="InvalidEntryStyle"
               TargetType="Entry">
            <Setter Property="TextColor" Value="IndianRed" />
        </Style>

        <Style x:Key="ValidEntryStyle"
               TargetType="Entry">
            <Setter Property="TextColor" Value="Green" />
        </Style>
    </pages:BasePage.Resources>
    <pages:BasePage.Content>
        <VerticalStackLayout
            Spacing="25"
            VerticalOptions="StartAndExpand">
            <Label
                Text="Text color will change accordingly to the style that is configured when an invalid string is entered." />

            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Label Text="CharacterType" />
                <Picker
                    x:Name="CharacterTypePicker"
                    Grid.Row="0"
                    Grid.Column="1"
                    Title="CharacterType"
                    ItemsSource="{Binding CharacterTypes, Mode=OneTime}" />
                <Label Grid.Row="1"
                       Grid.Column="0"
                       VerticalOptions="FillAndExpand"
                       VerticalTextAlignment="Center"
                       Text="MinimumCharacterCountEntry" />
                <Entry Grid.Row="1" Grid.Column="1"
                       x:Name="MinimumCharacterCountEntry"
                       Keyboard="Numeric"
                       Text="2"
                       VerticalOptions="FillAndExpand" />
                <Label Grid.Row="2"
                       Grid.Column="0"
                       VerticalOptions="FillAndExpand"
                       VerticalTextAlignment="Center"
                       Text="MaximumCharacterCountEntry" />
                <Entry Grid.Row="2" Grid.Column="1"
                       x:Name="MaximumCharacterCountEntry"
                       Keyboard="Numeric"
                       Text="20"
                       VerticalOptions="FillAndExpand" />
            </Grid>

            <Label Text="Type characters for validation behavior according to the settings you set upon." />
            <Entry Placeholder="Type characters...">
                <Entry.Behaviors>
                    <mct:CharactersValidationBehavior
                        CharacterType="{Binding SelectedItem, Source={x:Reference CharacterTypePicker}}"
                        Flags="ValidateOnValueChanged"
                        InvalidStyle="{StaticResource InvalidEntryStyle}"
                        ValidStyle="{StaticResource ValidEntryStyle}"
                        MaximumCharacterTypeCount="{Binding Text, Source={x:Reference MaximumCharacterCountEntry}}"
                        MinimumCharacterTypeCount="{Binding Text, Source={x:Reference MinimumCharacterCountEntry}}" />
                </Entry.Behaviors>
            </Entry>

            <Label Text="The same but styling handled by visual state manager." />
            <Entry Placeholder="Type characters...">
                <Entry.Behaviors>
                    <mct:CharactersValidationBehavior Flags="ValidateOnValueChanged"
                                                      CharacterType="{Binding SelectedItem, Source={x:Reference CharacterTypePicker}}"
                                                      MaximumCharacterTypeCount="{Binding Text, Source={x:Reference MaximumCharacterCountEntry}}"
                                                      MinimumCharacterTypeCount="{Binding Text, Source={x:Reference MinimumCharacterCountEntry}}" />
                </Entry.Behaviors>

                <VisualStateManager.VisualStateGroups>
                    <VisualStateGroupList>
                        <VisualStateGroup x:Name="CommonStates">
                            <VisualState x:Name="Valid">
                                <VisualState.Setters>
                                    <Setter Property="TextColor" Value="Green" />
                                </VisualState.Setters>
                            </VisualState>
                            <VisualState x:Name="Invalid">
                                <VisualState.Setters>
                                    <Setter Property="TextColor" Value="IndianRed" />
                                </VisualState.Setters>
                            </VisualState>
                        </VisualStateGroup>
                    </VisualStateGroupList>
                </VisualStateManager.VisualStateGroups>
            </Entry>

        </VerticalStackLayout>
    </pages:BasePage.Content>
</pages:BasePage>