我收到此错误,
LINQ中仅支持无参数构造函数和初始值设定项 实体。
经过研究,这似乎是许多答案的常见问题。除了我无法对很多答案进行逆向工程,因此我可以自己解决这个问题。
我意识到答案是在错误中,但是我无法看到需要使用无参数构造函数的东西?或者在这个例子中,我甚至不知道参数甚至在哪里???
这个LINQ查询给我带来了麻烦:
public static ObservableCollection<Employee> ReturnEmployeesInSection(string section)
{
using (StaffShiftManagerEntities dataBaseEntities = new StaffShiftManagerEntities())
{
return new ObservableCollection<Employee>(dataBaseEntities.Staff_Data_TBL
.Where(p => p.Section_Data == section && p.Staff_Bool == true)
.Select(staff => new Employee(staff.Staff_No ?? -1,
staff.Staff_Name_First, staff.Staff_Name_Second))
.ToList()
.GroupBy(staff => staff.Key)
.Select(staff => staff.First())
.OrderBy(staff => staff.Key)
.ToList());
}
}
Employee
类:
public class Employee
{
public int Key { get; set; }
public string FirstName { get; set; }
public string SecondName { get; set; }
public string FullName => FirstName + " " + SecondName;
public Employee(int key, string first = null, string second = null)
{
Key = key;
FirstName = first;
SecondName = second;
}
}
这是实体框架自动生成的类:
public partial class Staff_Data_TBL
{
public long ID { get; set; }
public byte[] Image_Col { get; set; }
public Nullable<int> Staff_No { get; set; }
public string Staff_Name_First { get; set; }
public string Staff_Name_Second { get; set; }
public string Section_Data { get; set; }
public string Lic_Data { get; set; }
public Nullable<System.DateTime> Start_Date { get; set; }
public Nullable<System.DateTime> End_Date { get; set; }
public Nullable<long> Night_1 { get; set; }
public Nullable<long> Night_2 { get; set; }
public Nullable<long> Lunch_Data { get; set; }
public Nullable<long> Unples_Data { get; set; }
public string Staff_Part { get; set; }
public bool Staff_Kaizen { get; set; }
public int StaffKaizenPercentage { get; set; }
public Nullable<bool> Staff_Bool { get; set; }
public string Group_Section_Data { get; set; }
public string Notes { get; set; }
}
请原谅命名约定,我正在将所有内容更改为更标准的命名。
答案 0 :(得分:2)
为ng-class="{'couldBeWrong':rid.indexOf('1A') > -1}"
类创建公共无参数构造函数。
Employee
使用对象初始值设定项而不是带参数的构造函数:
public Employee() {}
注意:正如您所见,我在结果投影之前移动了分组和排序。因此,您将在服务器端完成所有工作,而不是将表数据加载到内存中。
答案 1 :(得分:0)
更改
public class Employee
{
public Employee(){} //Constructor with no parameters that needs to be added
public int Key { get; set; }
public string FirstName { get; set; }
public string SecondName { get; set; }
public string FullName => FirstName + " " + SecondName;
public Employee(int key, string first = null, string second = null)
{
Key = key;
FirstName = first;
SecondName = second;
}
}
到
SELECT created_time, count(id) AS total
FROM `tweets`
WHERE created_time >= (NOW() - INTERVAL 10 DAY) AND active = 1
GROUP BY DATE(created_time)