/V2/trunk/RI/Silverlight/StockTraderRI.Infrastructure.Silverlight/SelectorExtensions.cs

//===================================================================================

// Microsoft patterns & practices

// Composite Application Guidance for Windows Presentation Foundation and Silverlight

//===================================================================================

// Copyright (c) Microsoft Corporation.  All rights reserved.

// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY

// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT

// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

// FITNESS FOR A PARTICULAR PURPOSE.

//===================================================================================

// The example companies, organizations, products, domain names,

// e-mail addresses, logos, people, places, and events depicted

// herein are fictitious.  No association with any real company,

// organization, product, domain name, email address, logo, person,

// places, or events is intended or should be inferred.

//===================================================================================

using System;

using System.Collections.Generic;

using System.Globalization;

using System.Linq;

using System.Reflection;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Controls.Primitives;

using StockTraderRI.Infrastructure.Properties;



namespace StockTraderRI.Infrastructure

{

    /// <summary>

    /// Defines the Attached Behavior needed to keep synchronized the selected value 

    /// of a <see cref="Selector"/> with a bound property.

    /// </summary>

    /// <remarks>This is to workaround the missing SelectedItem property that is present in WPF but not in Silverlight.</remarks>

    public static class SelectorExtensions

    {

        /// <summary>

        /// The property bound to the <see cref="Selector"/>'s selected value.

        /// </summary>

        public static readonly DependencyProperty SelectedValueProperty =

                DependencyProperty.RegisterAttached("SelectedValue", typeof(object), typeof(SelectorExtensions), new PropertyMetadata(SelectedValueChanged));



        /// <summary>

        /// The path to the bound property getter.

        /// </summary>

        public static readonly DependencyProperty SelectedValuePathProperty =

                DependencyProperty.RegisterAttached("SelectedValuePath", typeof(string), typeof(SelectorExtensions), new PropertyMetadata(SelectedValuePathChanged));



        private static readonly Dictionary<string, MethodInfo> cachedPropertyGetters = new Dictionary<string, MethodInfo>();



        /// <summary>

        /// Gets the <see cref="SelectedValueProperty"/> value.

        /// </summary>

        /// <param name="dependencyObject">The <see cref="DependencyObject"/> on which the attached property is set.</param>

        /// <returns>The value of the <see cref="SelectedValueProperty"/> property.</returns>

        public static object GetSelectedValue(DependencyObject dependencyObject)

        {

            return dependencyObject.GetValue(SelectedValueProperty);

        }



        /// <summary>

        /// Sets the <see cref="SelectedValueProperty"/> value.

        /// </summary>

        /// <param name="dependencyObject">The <see cref="DependencyObject"/> on which the attached property will be set.</param>

        /// <param name="value">Value to set to <see cref="SelectedValueProperty"/> attached property.</param>

        public static void SetSelectedValue(DependencyObject dependencyObject, object value)

        {

            dependencyObject.SetValue(SelectedValueProperty, value);

        }



        /// <summary>

        /// Gets the <see cref="SelectedValuePathProperty"/> value.

        /// </summary>

        /// <param name="dependencyObject">The <see cref="DependencyObject"/> on which the attached property is set.</param>

        /// <returns>The value of the <see cref="SelectedValuePathProperty"/> property.</returns>

        public static string GetSelectedValuePath(DependencyObject dependencyObject)

        {

            return dependencyObject.GetValue(SelectedValuePathProperty) as string;

        }



        /// <summary>

        /// Sets the <see cref="SelectedValuePathProperty"/> value.

        /// </summary>

        /// <param name="dependencyObject">The <see cref="DependencyObject"/> on which the attached property will be set.</param>

        /// <param name="value">Value to set to <see cref="SelectedValuePathProperty"/> attached property.</param>

        public static void SetSelectedValuePath(DependencyObject dependencyObject, string value)

        {

            dependencyObject.SetValue(SelectedValuePathProperty, value);

        }



        private static void SelectedValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

        {

            object newValue = e.NewValue;

            if (!Equals(newValue, e.OldValue))

            {

                Selector selector = d as Selector;

                if (selector != null)

                {

                    SyncronizeSelectedItem(selector, newValue);

                }

            }

        }



        private static void SyncronizeSelectedItem(Selector selector, object value)

        {

            string selectedValuePath = GetSelectedValuePath(selector);

            if (!string.IsNullOrEmpty(selectedValuePath))

            {

                if (selector.SelectedItem == null

                    || !Equals(GetValueForPath(selector.SelectedItem, selectedValuePath), value))

                {

                    object selectedItem =

                            selector.Items.FirstOrDefault(

                                    item => Equals(GetValueForPath(item, selectedValuePath), value));

                    selector.SelectedItem = selectedItem;

                }

            }

        }



        private static void SelectedValuePathChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

        {

            Selector selector = d as Selector;

            if (selector != null)

            {

                if (e.OldValue == null && e.NewValue != null)

                {

                    // Subscribes to selection changes in the Selector.

                    selector.SelectionChanged += SelectorSelectionChanged;

                }



                if (e.OldValue != null && e.NewValue == null)

                {

                    // Unsubscribes to clean up.

                    selector.SelectionChanged -= SelectorSelectionChanged;

                }



                SyncronizeSelectedItem(selector, GetSelectedValue(selector));

            }

        }



        private static void SelectorSelectionChanged(object sender, SelectionChangedEventArgs e)

        {

            Selector selector = (Selector)sender;

            object selectedItem = selector.SelectedItem;

            string selectedValuePath = GetSelectedValuePath(selector);

            object selectedValue = GetValueForPath(selectedItem, selectedValuePath);

            if (!Equals(GetSelectedValue(selector), selectedValue))

            {

                SetSelectedValue(selector, selectedValue);

            }

        }



        private static object GetValueForPath(object instance, string valuePath)

        {

            MethodInfo propertyGetter = GetPropertyGetterForType(instance.GetType(), valuePath);

            object returnValue = propertyGetter.Invoke(instance, null);

            return returnValue;

        }



        private static MethodInfo GetPropertyGetterForType(Type type, string memberName)

        {

            string hashKey = string.Format(CultureInfo.InvariantCulture, "{0}&{1}", type.AssemblyQualifiedName, memberName);

            MethodInfo methodInfo;

            if (!cachedPropertyGetters.TryGetValue(hashKey, out methodInfo))

            {

                PropertyInfo property = type.GetProperty(memberName);

                if (property != null)

                {

                    methodInfo = property.GetGetMethod();

                }



                cachedPropertyGetters.Add(hashKey, methodInfo);

            }



            if (methodInfo == null)

            {

                throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture, Resources.SelectorExtensionCannotResolveMember, type.FullName, memberName, typeof(SelectorExtensions).Name));

            }



            return methodInfo;

        }

    }

}