linq Distinct 去重

区分大小写

  public class RowComparer : IEqualityComparer<pt_registration >
    {
        CaseInsensitiveComparer myComparer = new CaseInsensitiveComparer ();
        public bool Equals(pt_registration t1, pt_registration t2)
        {
            if (myComparer.Compare(t1.emailAddress, t2.emailAddress) == 0 && myComparer.Compare(t1.firstName, t2.firstName) == 0 && myComparer.Compare(t1.lastName, t2.lastName) == 0)
            {
                return true ;
            } else
            {
                return false ;
            }
        }
        public int GetHashCode(pt_registration t)
        {
            return t.ToString().ToLowerInvariant().GetHashCode();
        }
    }

不区分大小写

 public class RowComparer : IEqualityComparer<pt_registration >
    {
        public bool Equals(pt_registration t1, pt_registration t2)
        {
            return (t1.emailAddress == t2.emailAddress && t1.firstName == t2.firstName &&t1.lastName==t2.lastName);
        }
        public int GetHashCode(pt_registration t)
        {
            return t.ToString().GetHashCode();
        }
    } 

在下边使用哦

   IEnumerable<pt_registration > distinctRows = (from n in db.pt_registrations
                                                         where n.bankID == BankID && (n.businessName == mybusiness.formal_name || n.businessName == "ALL" ) && n.timeRegistered >= Convert .ToDateTime(startDate) && n.timeRegistered < Convert .ToDateTime(endDate)
                                                         select n).ToList().Distinct(new RowComparer());
            IList<pt_registration > myRegList = distinctRows.ToList();
            GrVw_Registration.DataSource = myRegList;
            GrVw_Registration.DataBind();