WPF定番コード集その3。ComboBox

ComboBoxVM.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections.ObjectModel;

namespace TemplateApp.ViewModel
{
    public class ComboBoxVM<T> : ViewModelBase
    {
        private ObservableCollection<ComboBoxSelector<T>> candidates;
        public ObservableCollection<ComboBoxSelector<T>> Candidates
        {
            get { return candidates; }
            set { candidates = value; OnPropertyChanged(); }
        }

        private ComboBoxSelector<T> selectedItem;
        public ComboBoxSelector<T> SelectedItem
        {
            get { return selectedItem; }
            set { selectedItem = value; OnPropertyChanged(); }
        }

        public T SelectedItemValue
        {
            get { return SelectedItem == null ? default(T) : SelectedItem.Value; }
            set { SelectedItem = Candidates.FirstOrDefault(x => x.Value.Equals(value)); }
        }
        
        //パラメータから表示用の文字列に変換する関数
        public delegate string nameConverter(T value);

        public ComboBoxVM(IEnumerable<T> ts, T defaultValue)
            : this(ts.Select(x => new ComboBoxSelector<T>(x.ToString(), x)))
        {
            SelectedItemValue = defaultValue;
        }
        
        public ComboBoxVM(IEnumerable<T> ts)
            : this(ts.Select(x => new ComboBoxSelector<T>(x.ToString(), x)))
        {
            SelectedItem = Candidates.FirstOrDefault();
        }

        public ComboBoxVM(IEnumerable<T> ts, nameConverter func, T defaultValue)
            : this(ts.Select(x => new ComboBoxSelector<T>(func(x), x)))
        {
            SelectedItemValue = defaultValue;
        }

        public ComboBoxVM(IEnumerable<T> ts, nameConverter func)
            : this(ts.Select(x => new ComboBoxSelector<T>(func(x), x)))
        {
            SelectedItem = Candidates.FirstOrDefault();
        }

        protected ComboBoxVM(IEnumerable<ComboBoxSelector<T>> selectors)
        {
            Candidates = new ObservableCollection<ComboBoxSelector<T>>(selectors);
        }
    }
    
    public class ComboBoxEnumVM<T> : ComboBoxVM<T> where T : struct
    {
        public ComboBoxEnumVM(T defaultValue)
            : base(Enum.GetValues(typeof(T)).OfType<T>().Select(x => new ComboBoxSelector<T>(x.ToString(), x)))
        {
            SelectedItemValue = defaultValue;
        }

        public ComboBoxEnumVM()
            : base(Enum.GetValues(typeof(T)).OfType<T>().Select(x => new ComboBoxSelector<T>(x.ToString(), x)))
        {
            SelectedItem = Candidates.FirstOrDefault();
        }

        public ComboBoxEnumVM(nameConverter func, T defaultValue)
            : base(Enum.GetValues(typeof(T)).OfType<T>().Select(x => new ComboBoxSelector<T>(func(x), x)))
        {
            SelectedItemValue = defaultValue;
        }

        public ComboBoxEnumVM(nameConverter func)
            : base(Enum.GetValues(typeof(T)).OfType<T>().Select(x => new ComboBoxSelector<T>(func(x), x)))
        {
            SelectedItem = Candidates.FirstOrDefault();
        }
    }

    public class ComboBoxSelector<T>
    {
        public string Label { get; private set; }
        public T Value { get; private set; }

        public ComboBoxSelector(string label, T value)
        {
            Label = label;
            Value = value;
        }
    }
}

Dictionary1.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:TemplateApp">
    <!--ComboBoxVM/ComboBoxEnumVMをDataContextとするComboBoxのStyle-->
    <Style x:Key="ComboBoxStyleBase" TargetType="{x:Type ComboBox}">
        <Style.Setters>
            <Setter Property="ItemsSource" Value="{Binding Candidates}"/>
            <Setter Property="SelectedItem" Value="{Binding SelectedItem}"/>
            <Setter Property="ItemTemplate">
                <Setter.Value>
                    <DataTemplate>
                        <Label Content="{Binding Label}"/>
                    </DataTemplate>
                </Setter.Value>
            </Setter>
        </Style.Setters>
    </Style>
</ResourceDictionary>