ef core 全局过滤

 有些固定的条件，基本每个查询的时候需要带的条件，我们可以使用全局过滤来帮我们，这样后面的查询就不用每次都带条件了。

微软自带的：https://docs.microsoft.com/zh-cn/ef/core/querying/filters 

特殊针对的过滤：https://entityframework-plus.net/query-filter

准备:

nuget    Z.EntityFramework.Plus.EFCore

例子：

现在我的表中有4条数据，两条是不需要的，需要过滤这两条数据

我们过滤掉IsDeleted=1的数据

① 创建过滤配置文件  DbFilterConfiguration.cs

添加方法

  /// <summary>
        /// 初始化全局的过滤,如软自带的
        /// </summary>
        /// <param name="entityType">过滤</param>
        /// <param name="modelBuilder">builder</param>
        public static void InitGobalFilter(IMutableEntityType entityType, ModelBuilder modelBuilder)
        {
            if (modelBuilder == null)
            {
                return;
            }
            IEnumerable<IMutableProperty> props = entityType.GetProperties();
            if (props.Any(x => x.Name == "IsDeleted"))
            {
                ParameterExpression parameter = Expression.Parameter(entityType.ClrType, "e");
                byte defaultValue = 0;
                BinaryExpression body = Expression.Equal(
                    Expression.Call(typeof(EF), nameof(EF.Property), new[] { typeof(byte) }, parameter, Expression.Constant("IsDeleted")),
               Expression.Constant(defaultValue));
                modelBuilder.Entity(entityType.ClrType).HasQueryFilter(Expression.Lambda(body, parameter));
                //if (entityType.Name.ToLower().Contains("view"))
                //{
                //    modelBuilder.Query(entityType.ClrType).HasQueryFilter(Expression.Lambda(body, parameter));
                //}
                //else
                //{
                //modelBuilder.Entity(entityType.ClrType).HasQueryFilter(Expression.Lambda(body, parameter));
                //}
            }
        }

在上下文中的OnModelCreating方法添加代码

  protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            IEnumerable<Microsoft.EntityFrameworkCore.Metadata.IMutableEntityType> entityTypes = modelBuilder.Model.GetEntityTypes();
            foreach (Microsoft.EntityFrameworkCore.Metadata.IMutableEntityType entityType in entityTypes)
            {
                DbFilterConfiguration.InitGobalFilter(entityType, modelBuilder);
            }
        }

这样我们每次查询的时候都会把IsDeleted=1的数据过滤

②使用Z.EntityFramework.Plus.EFCore 针对表，视图强过滤

在DbFilterConfiguration.cs中加如下代码

 /// <summary>
        /// 正针对表进行过滤
        /// </summary>
        /// <param name="db"></param>
        public static void InitContextFilter(MyDbContext db)
        {
            //根据登入人,针对某些表进行过滤
            //db.Filter<ViewPFUser>(q => q.Where(x => x.IsDeleted == 0));
            //db.ViewPFUser.AsNoFilter() 取消过滤
            db.Filter<ViewPFUser>(q => q.Where(x => x.UserName == "admin"));
        }

效果：

  /// <summary>
        /// 测试EFCore
        /// </summary>
        /// <returns></returns>
        [AllowAnonymous]
        [HttpGet("Test")]
        public async Task<IActionResult> Test()
        {
            //admin,admin22
            List<PFUser> list2 = await _db.PFUser.AsNoTracking().ToListAsync();
　　　　　　　　//admin,admin22.admin44,admin456   取消过滤
            List<PFUser> list4 = await _db.PFUser.AsNoTracking().IgnoreQueryFilters().ToListAsync();
            //admin
            List<ViewPFUser> list3 = await _db.ViewPFUser.AsNoTracking().ToListAsync();
            //admin,admin22  取消针对性的过滤
            List<ViewPFUser> list5 = await _db.ViewPFUser.AsNoFilter().ToListAsync();

　　　　　　 ........
     }