--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SilverlightValidation/SilverlightValidation.PL/ViewModels/ViewModelBase.cs	Sat May 05 13:29:56 2012 +0100
@@ -0,0 +1,73 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+
+namespace SilverlightValidation.ViewModels
+{
+    public class ViewModelBase : INotifyPropertyChanged, INotifyDataErrorInfo
+    {
+        #region INotifyPropertyChanged method plus event
+
+        public event PropertyChangedEventHandler PropertyChanged = delegate { };
+
+        protected void RaisePropertyChanged(string propertyName)
+        {
+            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
+        }
+
+        #endregion
+
+        #region INotifyDataErrorInfo methods and helpers
+
+        private readonly Dictionary<string, List<string>> _errors = new Dictionary<string, List<string>>();
+
+        public void SetError(string propertyName, string errorMessage)
+        {
+            if (!_errors.ContainsKey(propertyName))
+                _errors.Add(propertyName, new List<string> { errorMessage });
+
+            RaiseErrorsChanged(propertyName);
+        }
+
+        protected void ClearError(string propertyName)
+        {
+            if (_errors.ContainsKey(propertyName))
+            {
+                _errors.Remove(propertyName);
+                RaiseErrorsChanged(propertyName);
+            }
+        }
+
+        protected void ClearAllErrors()
+        {
+            var errors = _errors.Select(error => error.Key).ToList();
+
+            foreach (var propertyName in errors)
+                ClearError(propertyName);
+        }
+
+        public void RaiseErrorsChanged(string propertyName)
+        {
+            ErrorsChanged(this, new DataErrorsChangedEventArgs(propertyName));
+        }
+
+        public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged = delegate { };
+
+        public IEnumerable GetErrors(string propertyName)
+        {
+            if (propertyName == null) return null;
+            return _errors.ContainsKey(propertyName)
+                    ? _errors[propertyName]
+                    : null;
+        }
+
+        public bool HasErrors
+        {
+            get { return _errors.Count > 0; }
+        }
+
+        #endregion
+    }
+}