[WIP] Add a sample Page for DataValidationErrors

samples/ControlCatalog/MainView.xaml

@@ -74,6 +74,9 @@
                ScrollViewer.VerticalScrollBarVisibility="Disabled">
         <pages:DataGridPage />
       </TabItem>
+      <TabItem Header="Data Validation">
+        <pages:DataValidationPage />
+      </TabItem>
       <TabItem Header="Date/Time Picker">
         <pages:DateTimePickerPage />
       </TabItem>

samples/ControlCatalog/Pages/DataValidationPage.axaml

@@ -0,0 +1,20 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:viewModels="clr-namespace:ControlCatalog.ViewModels"
+             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
+             x:DataType="viewModels:DataValidationViewModel"
+             x:Class="ControlCatalog.Pages.DataValidationPage">
+  <UserControl.DataContext>
+    <viewModels:DataValidationViewModel />
+  </UserControl.DataContext>
+  <StackPanel>
+    <TextBox Text="{Binding DataAnnotationsSample}"
+             DataValidationErrors.ErrorConverter="{Binding Converter}" />
+
+    <TextBox Text="{Binding ExceptionInsideSetterSample}"
+             DataValidationErrors.ErrorConverter="{Binding ExceptionConverter}" />
+  </StackPanel>
+</UserControl>
+

samples/ControlCatalog/Pages/DataValidationPage.axaml.cs

@@ -0,0 +1,19 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace ControlCatalog.Pages;
+
+public partial class DataValidationPage : UserControl
+{
+    public DataValidationPage()
+    {
+        InitializeComponent();
+    }
+
+    private void InitializeComponent()
+    {
+        AvaloniaXamlLoader.Load(this);
+    }
+}
+

samples/ControlCatalog/ViewModels/DataValidationViewModel.cs

@@ -0,0 +1,50 @@
+using System;
+using System.ComponentModel;
+using System.ComponentModel.DataAnnotations;
+using MiniMvvm;
+
+namespace ControlCatalog.ViewModels;
+
+public class DataValidationViewModel : ViewModelBase
+{
+    private string? _DataAnnotationsSample;
+
+    /// <summary>
+    /// Gets or sets an E-Mail-Address validated using annotations
+    /// </summary>
+    [Required]
+    [EmailAddress]
+    [MinLength(5)]
+    public string? DataAnnotationsSample
+    {
+        get => _DataAnnotationsSample;
+        set => RaiseAndSetIfChanged(ref _DataAnnotationsSample, value);
+    }
+
+    public Func<object, object> Converter { get; } = new Func<object, object>(o =>
+    {
+        return $"Error: {o}";
+    });
+
+
+    private string? _ExceptionInsideSetterSample;
+
+    /// <summary>
+    /// Gets or sets an E-Mail-Address validated using annotations
+    /// </summary>
+    public string? ExceptionInsideSetterSample
+    {
+        get => _ExceptionInsideSetterSample;
+        set
+        {
+            if (value is null || value.Length < 5) throw new ArgumentOutOfRangeException(nameof(value), "Give me 5 or more letter please :-)");
+
+            RaiseAndSetIfChanged(ref _ExceptionInsideSetterSample, value);
+        }
+    }
+
+    public Func<object, object> ExceptionConverter { get; } = new Func<object, object>(o =>
+    {
+        return o is Exception ex ? $"Huh, there was an Exception: {ex.Message}" : "Something went really wrong!";
+    });
+}