利用反射来实现类（含可空字段）的映射

   public override void MapToEntity(object obj)
        {
            DBSettleAccountWithWaitingSummary summary =( DBSettleAccountWithWaitingSummary)obj;
            Type entityType = this.GetType();
            PropertyInfo[] ePropertyInfos = entityType.GetProperties();
            string propertyName;
            foreach (PropertyInfo ePropertyInfo in ePropertyInfos)
            {
                propertyName=ePropertyInfo.Name;
                if (propertyName.Equals("GetAction") || propertyName.Equals("DisplayText")) continue;
                PropertyInfo dbPropertyInfo = summary.GetType().GetProperty(propertyName);
                ePropertyInfo.SetValue(this, dbPropertyInfo.GetValue(summary, null).ChangeType(ePropertyInfo.PropertyType), null);
            }

        }

public static class ZBConvert
    {
        public static object ChangeType(this object value, Type conversionType)
        {
            if (conversionType.IsGenericType && conversionType.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
            {
                if (value != null)
                {
                    NullableConverter nullableConverter = new NullableConverter(conversionType);
                    conversionType = nullableConverter.UnderlyingType;
                }
                else
                {
                    return null;
                }
            }

            return Convert.ChangeType(value, conversionType);
        }
    }