How do I get .Net Maui Validation working

Does anyone have a good solution for validating UI input in Maui?

The only real solution I saw was the validation in the community toolkit, but that doesn't even work, so looking for someone to advise on what to do...

Thanks

There are few ways to make such validation.

One way is using inheriting ObservableValidator.

public partial class MainViewModel : ObservableValidator
{
    [Required(ErrorMessage = "Text is Required Field!")]
    [MinLength(5,ErrorMessage = "Text length is minimum 5!")]
    [MaxLength(10, ErrorMessage = "Text length is maximum 10!")]
    [ObservableProperty]
    string _text = "Hello";

    [ObservableProperty]
    bool _isTextValid;

    [ObservableProperty]
    string _error;

    [RelayCommand]
    void Validate()
    {
        ValidateAllProperties();
        
        if (HasErrors)
            Error = string.Join(Environment.NewLine, GetErrors().Select(e => e.ErrorMessage));
        else
            Error = String.Empty;

        IsTextValid = (GetErrors().ToDictionary(k => k.MemberNames.First(), v => v.ErrorMessage) ?? new Dictionary<string, string?>()).TryGetValue(nameof(Text), out var error);
    }
}

This is the way you can do it in your ViewModel.

The second way is using behaviors.

 <Entry.Behaviors>
                <toolkit:EmailValidationBehavior InvalidStyle="{StaticResource InvalidEntryStyle}"
                                                      IsValid="{Binding EmailIsValid}"                                                
                                                      ValidStyle="{StaticResource NormalEntryStyle}"                                                     
                                                      Flags="ValidateOnValueChanged" >
                </toolkit:EmailValidationBehavior>
 </Entry.Behaviors>

This is how I do it with the XAML.

I use both, depending on what I want to do.