EF扩展 更新指定字段

using System.Data.Entity.Infrastructure;
using System.Threading.Tasks;

/// <summary>
    /// EF扩展
    /// </summary>
    public static class EFExtensions
    {
        /// <summary>
        /// 更新实体根据字段
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="db">数据库上下文</param>
        /// <param name="entity">实体</param>
        /// <param name="fields">更新的字段列表</param>
        public static int UpdateEntityFields<T>(this ApplicationDbContext db, T entity, IList<string> fields) where T : class
        {
            if (entity == null || fields == null || fields.Count == )
            {
                return ;
            }
            db.Set<T>().Attach(entity);
            var SetEntry = ((IObjectContextAdapter)db).ObjectContext.
                 ObjectStateManager.GetObjectStateEntry(entity);
            foreach (var item in fields)
            {
                SetEntry.SetModifiedProperty(item);
            }
            return db.SaveChanges();
        }

        /// <summary>
        /// 异步更新实体根据字段
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="db">数据库上下文</param>
        /// <param name="entity">实体</param>
        /// <param name="fields">更新字段列表</param>
        /// <returns>受影响的行数</returns>
        public static async Task<int> UpdateEntityFieldsAsync<T>(this ApplicationDbContext db, T entity, IList<string> fields) where T : class
        {
            if (entity == null || fields == null || fields.Count == )
            {
                return ;
            }
            db.Set<T>().Attach(entity);
            var SetEntry = ((IObjectContextAdapter)db).ObjectContext.
                 ObjectStateManager.GetObjectStateEntry(entity);
            foreach (var item in fields)
            {
                SetEntry.SetModifiedProperty(item);
            }
            int result = await db.SaveChangesAsync();
            return result;
        }
    }