最近使用LINQ遇到的故障

 

1.成员“YouXieKu.Models.Product.Published”不支持转换为 SQL

    public partial class Product{
            .......

        public bool Published
        {
            get
            {
                return (this.ReleaseDate <= DateTime.Now && (this.ExpireDate > DateTime.Now||this.ExpireDate==null)&&this.Storage.Count>0&&this.Approved==true);

            }
        }

}
可能原因：在执行LINQ查询时不该使用分部类中新增的属性值Published，直接通过原始值this.ReleaseDate <= DateTime.Now && (this.ExpireDate > DateTime.Now||this.ExpireDate==null)&&this.Storage.Count>0&&this.Approved==true去判断

提示：由于以前的函数求值超时，函数求值被禁用。必须继续执行才能重新启用函数求值

可能原因：这是因为调试时会自动对Local/Watch等窗口里面（或鼠标停留所在）的变量求值，为了防止用户写的程序错误（比如死循环），系统有一个超时限制， 如果某个属性的get中做了很复杂的操作（而不是简单地返回一个私有变量的话），就有可能超过这个时间限制（如果strPage很大的话，你的正则运算就 很可能会超时）。
可以禁用自动求值的功能：
工具 -> 选项 -> 调试 -> 常规 -> 启用属性求值和其他隐式函数调用
去掉前面打勾，不过这样就不会对属性变量自动求值了。

3.LINQ语句  运行的时候提示"不支持带有本地集合的查询"

List<Department> _departments = dataContext.Department.GetAllChildDepartments(department);

            var _ProductUnderDepartment =
                (from a in dataContext.Product
                 let departmentIds = from b in _departments
                                     select b.DepartmentID
                 where departmentIds.Contains(a.ProductID) == true && a.ReleaseDate <= DateTime.Now && (a.ExpireDate > DateTime.Now || a.ExpireDate == null) && a.Storage.Count > 0 && a.Approved == true
                 select a).ToList();

不使用let departmentIds = from b in _departments   select b.DepartmentID 来动态从本地集合 _department 获取一组查询

改用直接先从_departments获取一组查询 List<int> _departments = dataContext.Department.GetAllChildDepartments(department).Select(p=>p.DepartmentID).ToList();

            var ProductUnderDepartment =
                (from a in dataContext.Product
                 where _departments.Contains(a.ProductID) == true && a.ReleaseDate <= DateTime.Now && (a.ExpireDate > DateTime.Now || a.ExpireDate == null) && a.Storage.Count > 0 && a.Approved == true
                 select a).ToList();
            var _ProductUnderDepartment = (from b in ProductUnderDepartment
                                           let s = from c in b.Storage
                                                   select c.UnitsInStock
                                           where s != null && s.Sum() > 0
                                           select b).ToList();
            return _ProductUnderDepartment;