List<T>的对比

对于类型的对比，linq原来的对比是区分不了的。

对两个list进行查询交集方法。交集，并集的函数是直接用Linq的，这里不再写。

 List<T> intersectList = queryList.AsQueryable().Intersect(sqlList, new ListEquality<T>()).ToList();

  public class ListEquality<T> : IEqualityComparer<T> where T : new()
    {

        PropertyInfo[] propertys = typeof(T).GetProperties().Where(p => p.Name != "ParamInfo").Where(p => p.Name != "State").ToArray();


        public bool Equals(T x, T y)
        {
            foreach (var pe in propertys)
            {
                object o_x = pe.GetValue(x, null);
                object o_y = pe.GetValue(y, null);
                if (!object.Equals(o_x, o_y))
                {
                    return false;
                }
            }
            return true;
        }

        public int GetHashCode(T obj)
        {
            if (obj == null)
            {
                return 0;
            }
            else
            {
                return obj.ToString().GetHashCode();
            }
        }
    }

上面的代码明显是根据排除字段来对比的。如果你不想根据字段对比，那就不要排除。

 

通过主键属性来对比仅仅是主键的类

   public class ListKeyEquality<T> : IEqualityComparer<T> where T : new()
    {

        PropertyInfo[] propertys = typeof(T).GetProperties().Where(p => p.Name != "ParamInfo").Where(p => p.Name != "State").ToArray();
        public bool Equals(T x, T y)
        {
            foreach (var pe in propertys)
            {
                object[] allAttributes = pe.GetCustomAttributes(false);
                if (allAttributes.Count() == 0)
                {
                    continue;
                }
                if ((allAttributes.FirstOrDefault() as GrantAttribute).IsKey)
                {
                    object o_x = pe.GetValue(x, null);
                    object o_y = pe.GetValue(y, null);
                    if (!object.Equals(o_x, o_y))
                    {
                        return false;
                    }
                }

            }
            return true;
        }

        public int GetHashCode(T obj)
        {
            if (obj == null)
            {
                return 0;
            }
            else
            {
                return obj.ToString().GetHashCode();
            }
        }
    }

  public class GrantAttribute : Attribute
    {
        /// <summary>
        /// 是否xml类型
        /// </summary>
        public bool CheckXml { get; set; }
        /// <summary>
        /// 是否主键
        /// </summary>
        public bool IsKey { get; set; }
    }

类的主键属性调用也是很简单

    public class OrderInfo
    {
        /// <summary>
        /// 本系统订单ID
        /// </summary>
        [Grant(IsKey = true)]
        public Guid OrderId { get; set; }
    }