c#沙盒环境

我正在Visual Studio中做一个小沙箱项目。下面是我的代码:

namespace Andromeda.PCTools
{
    public partial class Sandbox : MetroForm
    {
        private AppDomain sandbox;
        public Sandbox()
        {
            InitializeComponent();
        }
        private void Sandbox_Load(object sender, EventArgs e)
        {
        }
        private void btnAdd_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog ofd = new OpenFileDialog() { Filter = "Applications|*.exe", ValidateNames = true, Multiselect = false })
            {
                if (ofd.ShowDialog() == DialogResult.OK)
                {
                    listBoxItems.Items.Add(ofd.FileName);
                }
            }
        }
        private void removeSelectedToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (listBoxItems.SelectedItems.Count != 0)
            {
                while (listBoxItems.SelectedIndex != -1)
                {
                    listBoxItems.Items.RemoveAt(listBoxItems.SelectedIndex);
                }
            }
        }
        private void btnLoad_Click(object sender, EventArgs e)
        {
            PermissionSet ps = new PermissionSet(PermissionState.None);
            ps.AddPermission(new SecurityPermission(SecurityPermissionFlag.Execution));
            AppDomainSetup setup = new AppDomainSetup();
            Evidence ev = new Evidence();
            //ev.AddHostEvidence(new Zone(SecurityZone.Internet));
            PermissionSet internetPS = SecurityManager.GetStandardSandbox(ev);
            setup.ApplicationBase = Path.GetFullPath(Application.StartupPath);

            //StrongName fullTrustAssembly = typeof(Sandboxer).Assembly.Evidence.GetHostEvidence<StrongName>();
            sandbox = AppDomain.CreateDomain(listBoxItems.SelectedItem.ToString(), ev, setup, ps);
            try
            {
                sandbox.ExecuteAssembly(listBoxItems.SelectedItem.ToString());
                btnLoad.Enabled = false;
                btnUnload.Enabled = true;
            }
            catch (Exception ex)
            {
                MessageBox.Show("The following error occurred!'n" + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
        private void btnUnload_Click(object sender, EventArgs e)
        {
            try
            {
                AppDomain.Unload(sandbox);
                btnLoad.Enabled = true;
                btnUnload.Enabled = false;
            }
            catch (Exception ex)
            {
                MessageBox.Show("The following error occurred!'n" + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
    }
}

但是我得到以下错误:

抛出异常:'System.Security. 'Andromeda中的安全异常. 4.0.exe("请求类型为‘System.Security.Permissions’的权限。FileIOPermission mscorlib,版本=4.0.0.0，文化=中性，PublicKeyToken=b77a5c561934e089'失败了。")

ps.AddPermission(new FileIOPermission(PermissionState.Unrestricted));