New Post: LoadExtension error

using System.ComponentModel.Composition;
using System.Windows.Forms;
using DotSpatial.Controls;

public partial class MainForm : Form
    {
        [Export("Shell", typeof(ContainerControl))]
        private static ContainerControl Shell;

        private AppManager appManager;

        public MainForm()
        {
            InitializeComponent();
            appManager = new AppManager();
            Shell = this;
            appManager.LoadExtensions();
        }
    }