对象集合去重问题？

List<Data> list = new List<Data>();

list.Add(new Data { Email = "123", Remark = "345" });
list.Add(new Data { Email = "abc", Remark = "456" });
list.Add(new Data { Email = "abc", Remark = "456" });
list.Add(new Data { Email = "abc", Remark = "789" });

//问题1：根据字段去重

//方法1

public class Data:IEquatable<Data>
{
    public string Email { get; set; }
    public string Remark { get; set; }

    public bool Equals( Data other)
    {
       return this.Email == other.Email;//根据某个或多个字段去重
    }
    public override int GetHashCode()
    {
       return Email.GetHashCode();
    }
}

List<Data> ll = list.Distinct().ToList();

//方法2

public class UserComparer : IEqualityComparer<Data>
{
     public bool Equals(Data x, Data y)
     {
        if (x == null && y == null)
        {
          return false;
        }
        return x.Email.ToUpper() == y.Email.ToUpper();
     }
     public int GetHashCode(Data obj)
    {
        return obj.ToString().GetHashCode();
    }
}

 List<Data> l2 = list.Distinct(new UserComparer()).ToList();

//方法3
List<Data> l3 = list.Where((x, i) => list.FindIndex(z => z.Email == x.Email) == i).ToList();

//问题2：去重完全相同的对象

//方法1
var list1 = list.Select(a => new { Email = a.Email, ReMark = a.Remark }).Distinct();

//方法2
var list2 = (from q in list
select new
{
   Email = q.Email,
   Remark = q.Remark
}).Distinct();