错误：找不到当前平台的SQLite Wrapper程序集

Question

我的申请结构

内容主页

using MyBD;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.ApplicationModel.Background;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
namespace MyApp
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
            this.NavigationCacheMode = NavigationCacheMode.Required;
        }
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
        }

        private void button_Click(object sender, RoutedEventArgs e)
        {
            historyBD HBD = new historyBD("history");
        }
    }
}

内容MyBD

using SQLitePCL;
namespace MyBD
{
    public class historyBD
    {
        public SQLiteConnection con;
        private string mynull = "0";
        public historyBD(string dbname)
        {
            con = new SQLiteConnection(dbname);
        }
    }
}

当你按下按钮时，行“con = new SQLiteConnection（dbname）;” 给出错误消息：“找不到当前平台的SQLite Wrapper程序集。确保当前项目引用SQLitePCL和以下特定于平台的程序集：SQLitePCL.Ext。”

我做错了什么？