EnumProvider.cs

/* EnumProvider.cs
 * part of Daniel's XL Toolbox NG
 * 
 * Copyright 2014-2018 Daniel Kraus
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Reflection;
using Bovender.Mvvm.ViewModels;

namespace Bovender.Mvvm
{
    [Serializable]
    public class EnumProvider<T> : INotifyPropertyChanged where T: struct, IConvertible
    {
        #region Public properties

        public T AsEnum
        {
            get
            {
                return _selectedItem.Value;
            }
            set
            {
                _selectedItem = GetViewModel(value);
                AllPropertiesChanged();
            }
        }

        public EnumViewModel<T> SelectedItem
        {
            get
            {
                return _selectedItem;
            }
            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException(
                        "SelecteItem cannot be null because enums are not nullable.");
                }
                _selectedItem = value;
                AllPropertiesChanged();
            }
        }

        public string ToolTip
        {
            get
            {
                return SelectedItem.ToolTip;
            }
        }

        public IEnumerable<EnumViewModel<T>> Choices
        {
            get
            {
                if (_choices == null)
                {
                    _choices = new Collection<EnumViewModel<T>>();
                    foreach (T member in Enum.GetValues(typeof(T)))
                    {
                        EnumViewModel<T> vm = new EnumViewModel<T>(
                            member,
                            GetDescription(member),
                            GetTooltip(member));
                        vm.PropertyChanged += EnumViewModel_PropertyChanged;
                        _choices.Add(vm);
                    }
                }
                return _choices;
            }
        }

        #endregion

        #region Constructors

        public EnumProvider() {}

        public EnumProvider(T initialValue)
            : this()
        {
            AsEnum = initialValue;
        }

        #endregion

        #region Virtual methods

        protected virtual string GetDescription(T member)
        {
            Type type = typeof(T);
            MemberInfo[] memberInfo = type.GetMember(member.ToString());
            object[] attributes = memberInfo[0].GetCustomAttributes(
                typeof(DescriptionAttribute), false);
            if (attributes.Length > 0 && attributes[0] is DescriptionAttribute)
            {
                return ((DescriptionAttribute)attributes[0]).Description;
            }
            else
            {
                return member.ToString();
            }
        }

        protected virtual string GetTooltip(T member)
        {
            return null;
        }

        void EnumViewModel_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            if (sender == SelectedItem)
            {
                OnPropertyChanged("SelectedItem");
            }
            OnPropertyChanged("Choices");
        }

        #endregion

        #region Public methods

        public EnumViewModel<T> GetViewModel(T member)
        {
            return Choices.FirstOrDefault(item => item.Value.Equals(member));
        }

        #endregion

        #region Private methods

        private void AllPropertiesChanged()
        {
                OnPropertyChanged("SelectedItem");
                OnPropertyChanged("AsEnum");
                OnPropertyChanged("Tooltip");
        }

        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #endregion

        #region INotifyPropertyChanged

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion

        #region Private fields

        private EnumViewModel<T> _selectedItem;
        private Collection<EnumViewModel<T>> _choices;

        #endregion
    }
}