Matcha Validation Plugin an Unobtrusive Validation for Xamarin.Forms

A plugin library for unobtrusive "Testable" validation that works well with any MVVM framework , You can create a Customized Rule which perfectly fit to your needs.

Nuget

Matcha.Validation

Get Started

Using ValidationService

With ValidationService you can easily validate the viewmodel that derives from any MVVM framework base viewmodel class, this makes it very powerful and testable at the same time.

public class PrismTabbedPageViewModel : BindableBase
{
   private ValidationService<PrismTabbedPageViewModel> _validationService;

   public PrismTabbedPageViewModel()
   {
   	ValidationService = new ValidationService<PrismTabbedPageViewModel>(this);
   }

   public ValidationService<PrismTabbedPageViewModel> ValidationService
   {
   	get => _validationService;
   	set => SetProperty(ref _validationService, value);
   }
}

ValidationRule

When deriving ValidationRule, this will enables validation of the viewmodels property, The validation could be anything from email, null, greaterthanzero or it could be your custom validation (take EmailRule as an example).

public class IsNotNullOrEmptyRule : ValidationRule<string>
{
   public IsNotNullOrEmptyRule(string propertyName) : base(propertyName)
   {
   	ValidationMessage = $"{propertyName} should not be empty!";
   }

   protected override bool CheckValue(string value)
   {
   	return IsValid = !string.IsNullOrWhiteSpace(value);
   }
}

Adding the ValidationRule to ValidationService

ValidationRule is a bindable class this what makes the Matcha Validation so powerful because of its pure unobtrusive and it doesnt require custom control to handle it.

public PrismTabbedPageViewModel()
{
   ValidationService = new ValidationService<PrismTabbedPageViewModel>(this);
   EntryNotEmptyRule = ValidationService.Add(e => new IsNotNullOrEmptyRule(nameof(e.UserName))); //
}

Check if all Rule is Valid

ValidationRule is a bindable class this what makes the Matcha Validation so powerful because of its pure unobtrusive and it doesnt require custom control to handle it.

if (ValidationService.IsValid)
{
   //You code here when all rule's are valid
}

XAML Page

<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage
   x:Class="Sample.Views.PrismTabbedPage"
   xmlns="http://xamarin.com/schemas/2014/forms"
   xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
   xmlns:converter="clr-namespace:Sample.Converter;assembly=Sample"
   xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
   prism:ViewModelLocator.AutowireViewModel="True">
   <TabbedPage.Resources>
       <ResourceDictionary>
           <converter:InverseBooleanConverter x:Key="BooleanConverter" />
       </ResourceDictionary>
   </TabbedPage.Resources>
   <ContentPage Title="Custom Validation">
       <StackLayout Padding="30">
           <Entry Placeholder="Username" Text="{Binding UserName}" />
           <Label
               FontSize="Micro"
               IsVisible="{Binding EntryNotEmptyRule.IsValid, Converter={StaticResource BooleanConverter}}"
               Text="{Binding EntryNotEmptyRule.ValidationMessage}"
               TextColor="Red" />
           <Button
               Command="{Binding ValidateBuilInCommand}"
               IsEnabled="{Binding ValidationService.IsValid}"
               Text="Validate" />
       </StackLayout>
   </ContentPage>
</TabbedPage>

Preview

Platform Supported

Platform	Version
Xamarin.iOS	iOS 7+
Xamarin.Android	API 15+
Windows 10 UWP	10+
Xamarin.Mac	All
Xamarin.tvOS	All
Xamarin.watchOS	All
.NET Standard	2.0+
.NET Core	2.0+