void Main()
{
  List<Employee> emplist1 = new List<Employee>() { new Employee() { Id = 1, Name = "Scott" }, new Employee() { Id = 2, Name = "Lilly" }, new Employee() { Id = 3, Name = "Peter" } };
  List<Employee> emplist2 = new List<Employee>() { new Employee() { Id = 1, Name = "Scott" }, new Employee() { Id = 4, Name = "Kate" } };

  foreach (var r in emplist1.Except(emplist2,new EmployeeComparer()))
  {
  Console.WriteLine("{0},{1}", r.Id, r.Name);
  }
   /*
    2,Lilly
    3,Peter
   */

}
class Employee
  {
    private int id;
    private string name;
    
    public string Name
    {
    get { return name; }
    set { name = value; }
    }
    public int Id
    {
    get { return id; }
    set { id = value; }
    }
  }
  
  class EmployeeComparer : IEqualityComparer<Employee>
{
    // Products are equal if their names and product numbers are equal.
    public bool Equals(Employee x, Employee y)
    {

        //Check whether the compared objects reference the same data.
        if (Object.ReferenceEquals(x, y)) return true;

        //Check whether any of the compared objects is null.
        if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
            return false;

        //Check whether the products' properties are equal.
        return x.Id == y.Id && x.Name == y.Name;
    }

    // If Equals() returns true for a pair of objects 
    // then GetHashCode() must return the same value for these objects.

    public int GetHashCode(Employee ep)
    {
        //Check whether the object is null
        if (Object.ReferenceEquals(ep, null)) return 0;

        //Get hash code for the Name field if it is not null.
        int hashEmployeeName = ep.Name == null ? 0 : ep.Name.GetHashCode();

        //Get hash code for the Code field.
        int hashEmployeeId = ep.Id.GetHashCode();

        //Calculate the hash code for the product.
        return hashEmployeeName ^ hashEmployeeId;
    }

}

------解决方案--------------------

http://msdn.microsoft.com/en-us/library/bb336390.aspx