Commit 27f8b3c

@@ -0,0 +1,114 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Linq.Expressions;
+using gorilla.utility;
+
+namespace solidware.financials.windows.ui.presenters.validation
+{
+    public class Notification<T> : IDataErrorInfo
+    {
+        IDictionary<string, IList<IRule>> validationRules = new Dictionary<string, IList<IRule>>();
+
+        public void Register<Severity>(Expression<Func<T, object>> property, Func<bool> failCondition, Func<string> errorMessage) where Severity : ISeverity, new()
+        {
+            Register(property, new AnonymousRule<Severity>(failCondition, errorMessage));
+        }
+
+        public void Register(Expression<Func<T, object>> property, IRule rule)
+        {
+            EnsureRulesAreInitializeFor(property);
+            validationRules[property.pick_property().Name].Add(rule);
+        }
+
+        public string this[Expression<Func<T, object>> property] { get { return this[property.pick_property().Name]; } }
+        public string this[string propertyName]
+        {
+            get
+            {
+                if (!validationRules.ContainsKey(propertyName)) return null;
+                var validationRulesForProperty = validationRules[propertyName];
+                return validationRulesForProperty.Any(x => x.IsViolated())
+                           ? BuildErrorsFor(validationRulesForProperty)
+                           : null;
+            }
+        }
+
+        public string Error
+        {
+            get { throw new NotImplementedException(); }
+        }
+
+        public bool AreAnyRulesViolatedAndMoreSevereThan<Severity>() where Severity : ISeverity, new()
+        {
+            return validationRules.Any(validationRule => validationRule.Value.Any(x => x.IsViolatedAndMoreSevereThan<Severity>()));
+        }
+
+        void EnsureRulesAreInitializeFor(Expression<Func<T, object>> property)
+        {
+            if (!validationRules.ContainsKey(property.pick_property().Name))
+                validationRules[property.pick_property().Name] = new List<IRule>();
+        }
+
+        string BuildErrorsFor(IEnumerable<IRule> validationRulesForProperty)
+        {
+            var errors = new List<string>();
+            validationRulesForProperty.each(x =>
+            {
+                if (x.IsViolated()) errors.Add(x.ErrorMessage);
+            });
+            return string.Join(Environment.NewLine, errors.ToArray());
+        }
+    }
+    public interface IRule
+    {
+        bool IsViolated();
+        string ErrorMessage { get; }
+        bool IsViolatedAndMoreSevereThan<Severity>() where Severity : ISeverity, new();
+    }
+    public interface ISeverity
+    {
+        bool IsMoreSevereThan<OtherSeverity>(OtherSeverity otherSeverity) where OtherSeverity : ISeverity;
+    }
+    public class Warning : ISeverity
+    {
+        public bool IsMoreSevereThan<OtherSeverity>(OtherSeverity otherSeverity) where OtherSeverity : ISeverity
+        {
+            return !(otherSeverity is Error);
+        }
+    }
+    public class Error : ISeverity
+    {
+        public bool IsMoreSevereThan<OtherSeverity>(OtherSeverity otherSeverity) where OtherSeverity : ISeverity
+        {
+            return true;
+        }
+    }
+    public class AnonymousRule<Severity> : IRule where Severity : ISeverity, new()
+    {
+        readonly Func<bool> failCondition;
+        readonly Func<string> errorMessage;
+
+        public AnonymousRule(Func<bool> failCondition, Func<string> errorMessage)
+        {
+            this.failCondition = failCondition;
+            this.errorMessage = errorMessage;
+        }
+
+        public string ErrorMessage
+        {
+            get { return errorMessage(); }
+        }
+
+        public bool IsViolatedAndMoreSevereThan<OtherSeverity>() where OtherSeverity : ISeverity, new()
+        {
+            return IsViolated() && new Severity().IsMoreSevereThan(new OtherSeverity());
+        }
+
+        public bool IsViolated()
+        {
+            return failCondition();
+        }
+    }
+}
\ No newline at end of file

@@ -114,6 +114,7 @@
     <Compile Include="bootstrappers\ComposeShell.cs" />
     <Compile Include="bootstrappers\ConfigureMappings.cs" />
     <Compile Include="bootstrappers\DefaultMapper.cs" />
+    <Compile Include="presenters\validation\Notification.cs" />
     <Compile Include="presenters\SingleStockPresenter.cs" />
     <Compile Include="RunInBackgroundInterceptor.cs" />
     <Compile Include="bootstrappers\StopEssentialServices.cs" />