linq 从数组中排除部分项

public partial class Test : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        List<string> depts = new List<string>();//所有部门
        depts.Add("1");
        depts.Add("2");
        depts.Add("3");
        depts.Add("4");
        depts.Add("5");
        depts = DeptExclude1.Exclude(depts);
        foreach (string d in depts)
        {
            Response.Write(d.ToString()+"<br/>");
        }

    }
}

public class DeptExclude1
{
    public static  List<string> ex  = new List<string>();//需要排除集合
   
    public static  List<string> Exclude(List<string> depts)
    {
        ex.Add("1");
        ex.Add("2");
        ex.Add("3");
      
        return depts.Where(d=>ex.All(e=>e!=d)).ToList();
    }
}