WPF 2015 Visual Studio DatePicker using C#

我有一个关于工具箱中的DatePicker的问题。我试图在WPF中为用户创建一个程序，从两个日期选择器中选择两个日期，并根据这些日期确定它们之间的天数。

我在网上找到了另一种叫做DateTimePicker的工具，它似乎更容易使用。但是，这并不包括在我的工具箱中，所以我不得不使用datepicker类。到目前为止，我的cs代码如下所示:

using System;
using System.Collections.Generic;
namespace DateDifference
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

        }

        public static object RadDatePickerStart { get; private set; }
        private void button_Click(object sender, RoutedEventArgs e)
        {

        }

        private void startDate_SelectedDateChanged(object sender, SelectionChangedEventArgs e)
        {
            // ... Get DatePicker reference.
            var picker = sender as DatePicker;
            // ... Get nullable DateTime from SelectedDate.
            DateTime? date = picker.SelectedDate;
            if (date == null)
            {
                // ... A null object.
                this.Title = "No date";
            }
            else
            {
                // ... No need to display the time.
                this.Title = "Program for calculating difference between dates";
                textBoxResult.Text = date.Value.ToShortDateString();
            }
        }
        private void endDate_SelectedDateChanged_1(object sender, SelectionChangedEventArgs e)
        {
            // ... Get DatePicker reference.
            var picker = sender as DatePicker;
            // ... Get nullable DateTime from SelectedDate.
            DateTime? date = picker.SelectedDate;
            if (date == null)
            {
                // ... A null object.
                this.Title = "No date";
            }
            else
            {
                // ... No need to display the time.
                this.Title = "Program for calculating difference between dates";
                textBoxResult.Text = date.Value.ToShortDateString();
            }
        }
    }
}

所以我的问题是如何得到这个datepicker类的天的差异?

致以最亲切的问候!

(EndDate - StartDate).TotalDays