Building WPF Applications with Self-Tracking Entity Generator and Visual Studio 2012 - Project Setup

using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using SchoolSample.EntityModel;

namespace SchoolSample
{
    public static class ValidationSummaryBehavior
    {
        #region "TargetofObjectError"

        public static IObjectWithChangeTracker GetTargetofObjectError(ValidationSummary validationSummary)
        {
            return (IObjectWithChangeTracker) validationSummary.GetValue(TargetofObjectErrorProperty);
        }

        public static void SetTargetofObjectError(ValidationSummary validationSummary, IObjectWithChangeTracker value)
        {
            validationSummary.SetValue(TargetofObjectErrorProperty, value);
        }

        public static readonly DependencyProperty TargetofObjectErrorProperty =
            DependencyProperty.RegisterAttached(
                "TargetofObjectError",
                typeof (IObjectWithChangeTracker),
                typeof (ValidationSummaryBehavior),
                new UIPropertyMetadata(null, OnTargetofObjectErrorChanged));

        private static readonly List<KeyValuePair<IObjectWithChangeTracker, ValidationSummary>> KeyValuePairs =
            new List<KeyValuePair<IObjectWithChangeTracker, ValidationSummary>>();

        private static void OnTargetofObjectErrorChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)
        {
            var validationSummary = depObj as ValidationSummary;

            if (validationSummary == null) return;

            if (e.OldValue is IObjectWithChangeTracker)
            {
                foreach (var keyValuePair in KeyValuePairs
                    .Where(item => item.Key.Equals(e.OldValue) && item.Value.Equals(validationSummary))
                    .ToList())
                {
                    KeyValuePairs.Remove(keyValuePair);
                }

                if (e.OldValue is INotifyDataErrorInfo)
                {
                    ((INotifyDataErrorInfo) e.OldValue).ErrorsChanged -= ValidationSummaryBehavior_ErrorsChanged;
                }
            }

            if (e.NewValue is IObjectWithChangeTracker)
            {
                KeyValuePairs.Add(
                    new KeyValuePair<IObjectWithChangeTracker, ValidationSummary>(
                        (IObjectWithChangeTracker) e.NewValue, validationSummary));

                if (e.NewValue is INotifyDataErrorInfo)
                {
                    ((INotifyDataErrorInfo) e.NewValue).ErrorsChanged += ValidationSummaryBehavior_ErrorsChanged;
                }
            }
        }

        private static void ValidationSummaryBehavior_ErrorsChanged(object sender, DataErrorsChangedEventArgs e)
        {
            var item = sender as IObjectWithChangeTracker;

            if (item != null)
            {
                foreach (ValidationSummary validationSummary in KeyValuePairs
                    .Where(n => n.Key.Equals(item)).Select(n => n.Value))
                {
                    // remove all existing ObjectError
                    foreach (var validationSummaryItem in validationSummary.Errors
                        .Where(n => n.ItemType == ValidationSummaryItemType.ObjectError).
                        ToList())
                    {
                        validationSummary.Errors.Remove(validationSummaryItem);
                    }
                    // update ObjectError
                    var iNotifyDataErrorInfo = item as INotifyDataErrorInfo;
                    if (iNotifyDataErrorInfo != null && iNotifyDataErrorInfo.GetErrors(string.Empty) != null)
                    {
                        foreach (System.ComponentModel.DataAnnotations.ValidationResult validationResult in
                            iNotifyDataErrorInfo.GetErrors(string.Empty))
                        {
                            validationSummary.Errors.Add(new ValidationSummaryItem(validationResult.ErrorMessage));
                        }
                    }
                }
            }
        }

        #endregion "TargetofObjectError"
    }
}