UpDown editors: due to a bug in Visual Studio, you cannot create event handlers for events that have generic or nullable event args in XAML. So I changed the event args to object to support the design experience, but this now forces you to cast the result of the new value to the appropriate data type.

Various bug fixes

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/Calculator/Implementation/Calculator.cs

@@ -169,7 +169,7 @@ namespace Microsoft.Windows.Controls
             else
                 DisplayText = "0";
 
-            RoutedPropertyChangedEventArgs<decimal?> args = new RoutedPropertyChangedEventArgs<decimal?>(oldValue, newValue);
+            RoutedPropertyChangedEventArgs<object> args = new RoutedPropertyChangedEventArgs<object>(oldValue, newValue);
             args.RoutedEvent = ValueChangedEvent;
             RaiseEvent(args);
         }
@@ -433,8 +433,9 @@ namespace Microsoft.Windows.Controls
 
         #region Events
 
-        public static readonly RoutedEvent ValueChangedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<decimal?>), typeof(Calculator));
-        public event RoutedPropertyChangedEventHandler<decimal?> ValueChanged
+        //Due to a bug in Visual Studio, you cannot create event handlers for nullable args in XAML, so I have to use object instead.
+        public static readonly RoutedEvent ValueChangedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<object>), typeof(Calculator));
+        public event RoutedPropertyChangedEventHandler<object> ValueChanged
         {
             add { AddHandler(ValueChangedEvent, value); }
             remove { RemoveHandler(ValueChangedEvent, value); }

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/Core/Primitives/UpDownBase.cs

@@ -57,27 +57,13 @@ namespace Microsoft.Windows.Controls.Primitives
 
         #region Value
 
-        public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value", typeof(T), typeof(UpDownBase<T>), new FrameworkPropertyMetadata(default(T), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnValueChanged, OnCoerceValue));
+        public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value", typeof(T), typeof(UpDownBase<T>), new FrameworkPropertyMetadata(default(T), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnValueChanged));
         public T Value
         {
             get { return (T)GetValue(ValueProperty); }
             set { SetValue(ValueProperty, value); }
         }
 
-        private static object OnCoerceValue(DependencyObject o, object value)
-        {
-            UpDownBase<T> upDownBase = o as UpDownBase<T>;
-            if (upDownBase != null)
-                return upDownBase.OnCoerceValue((T)value);
-            else
-                return value;
-        }
-
-        protected virtual T OnCoerceValue(T value)
-        {
-            return value;
-        }
-
         private static void OnValueChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
         {
             UpDownBase<T> upDownBase = o as UpDownBase<T>;
@@ -87,9 +73,11 @@ namespace Microsoft.Windows.Controls.Primitives
 
         protected virtual void OnValueChanged(T oldValue, T newValue)
         {
+            CoerceValue(newValue);
+
             SyncTextAndValueProperties(ValueProperty, string.Empty);
 
-            RoutedPropertyChangedEventArgs<T> args = new RoutedPropertyChangedEventArgs<T>(oldValue, newValue);
+            RoutedPropertyChangedEventArgs<object> args = new RoutedPropertyChangedEventArgs<object>(oldValue, newValue);
             args.RoutedEvent = ValueChangedEvent;
             RaiseEvent(args);
         }
@@ -197,8 +185,9 @@ namespace Microsoft.Windows.Controls.Primitives
 
         #region Events
 
-        public static readonly RoutedEvent ValueChangedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<T>), typeof(UpDownBase<T>));
-        public event RoutedPropertyChangedEventHandler<T> ValueChanged
+        //Due to a bug in Visual Studio, you cannot create event handlers for generic T args in XAML, so I have to use object instead.
+        public static readonly RoutedEvent ValueChangedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<object>), typeof(UpDownBase<T>));
+        public event RoutedPropertyChangedEventHandler<object> ValueChanged
         {
             add { AddHandler(ValueChangedEvent, value); }
             remove { RemoveHandler(ValueChangedEvent, value); }
@@ -268,6 +257,23 @@ namespace Microsoft.Windows.Controls.Primitives
 
         #region Abstract
 
+
+        /// <summary>
+        /// Coerces the value.
+        /// </summary>
+        protected abstract void CoerceValue(T value);
+
+        /// <summary>
+        /// Converts the formatted text to a value.
+        /// </summary>
+        protected abstract T ConvertTextToValue(string text);
+
+        /// <summary>
+        /// Converts the value to formatted text.
+        /// </summary>
+        /// <returns></returns>
+        protected abstract string ConvertValueToText();
+
         /// <summary>
         /// Called by OnSpin when the spin direction is SpinDirection.Increase.
         /// </summary>
@@ -278,10 +284,6 @@ namespace Microsoft.Windows.Controls.Primitives
         /// </summary>
         protected abstract void OnDecrement();
 
-        protected abstract T ConvertTextToValue(string text);
-
-        protected abstract string ConvertValueToText();
-
         #endregion //Abstract
 
         #endregion //Methods

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/DateTimeUpDown/Implementation/DateTimeUpDown.cs

@@ -128,6 +128,11 @@ namespace Microsoft.Windows.Controls
             TextBox.SelectionChanged += TextBox_SelectionChanged;
         }
 
+        protected override void CoerceValue(DateTime? value)
+        {
+            //TODO: implement Min and Max values and keep the Value between those parameters
+        }
+
         protected override void OnIncrement()
         {
             if (Value.HasValue)
@@ -186,17 +191,6 @@ namespace Microsoft.Windows.Controls
             SyncTextAndValueProperties(InputBase.TextProperty, result.ToString());
         }
 
-        protected override DateTime? OnCoerceValue(DateTime? value)
-        {
-            //if the user entered a string value to represent a date or time, we need to parse that string into a valid DatTime value
-            if (value != null && !(value is DateTime))
-            {
-                return DateTime.Parse(value.ToString(), DateTimeFormatInfo);
-            }
-
-            return value;
-        }
-
         protected override DateTime? ConvertTextToValue(string text)
         {
             if (string.IsNullOrEmpty(text))

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/NumericUpDown/Implementation/DecimalUpDown.cs

@@ -20,14 +20,12 @@ namespace Microsoft.Windows.Controls
 
         #region Base Class Overrides
 
-        protected override decimal? OnCoerceValue(decimal? value)
+        protected override void CoerceValue(decimal? value)
         {
             if (value < Minimum)
-                return Minimum;
+                Value = Minimum;
             else if (value > Maximum)
-                return Maximum;
-            else
-                return value;
+                Value = Maximum;
         }
 
         protected override void OnIncrement()

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/NumericUpDown/Implementation/DoubleUpDown.cs

@@ -20,14 +20,12 @@ namespace Microsoft.Windows.Controls
 
         #region Base Class Overrides
 
-        protected override double? OnCoerceValue(double? value)
+        protected override void CoerceValue(double? value)
         {
             if (value < Minimum)
-                return Minimum;
+                Value = Minimum;
             else if (value > Maximum)
-                return Maximum;
-            else
-                return value;
+                Value = Maximum;
         }
 
         protected override void OnIncrement()

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/NumericUpDown/Implementation/IntegerUpDown.cs

@@ -20,14 +20,12 @@ namespace Microsoft.Windows.Controls
 
         #region Base Class Overrides
 
-        protected override int? OnCoerceValue(int? value)
+        protected override void CoerceValue(int? value)
         {
             if (value < Minimum)
-                return Minimum;
+                Value = Minimum;
             else if (value > Maximum)
-                return Maximum;
-            else
-                return value;
+                Value = Maximum;
         }
 
         protected override void OnIncrement()

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/RichTextBoxFormatBar/RichTextBoxFormatBarManager.cs

@@ -127,7 +127,10 @@ namespace Microsoft.Windows.Controls
             VerifyAdornerLayer();
 
             Control adorningEditor = _toolbar as Control;
-            _adorner.Child = adorningEditor;
+
+            if (_adorner.Child == null)
+                _adorner.Child = adorningEditor;
+
             _adorner.Visibility = Visibility.Visible;
 
             PositionFormatBar(adorningEditor);
@@ -184,7 +187,7 @@ namespace Microsoft.Windows.Controls
             if (IsAdornerVisible)
             {
                 _adorner.Visibility = Visibility.Collapsed;
-                _adorner.Child = null;
+                //_adorner.Child = null;
             }
         }