c# - 根据参数获取员工子集

Question

我已经在存储过程中完成了带排序的分页。但是现在，我需要在 LINQ 中为以下对象执行相同的操作。在以下场景中实现排序和分页的最可读 LINQ 查询是什么？

代码

static  List<Employee> GetMyData(int pageIndex, int pageSize, out int itemCount, string sortField, string sortDirection )
{

    Employee e1= new Employee(){EmpID = 1, EmpName = "E1"};
    Employee e2= new Employee(){EmpID = 2, EmpName = "E2"};
    Employee e3= new Employee(){EmpID = 3, EmpName = "E3"};
    Employee e4= new Employee(){EmpID = 4, EmpName = "E4"};
    Employee e5= new Employee(){EmpID = 5, EmpName = "E5"};
    Employee e6= new Employee(){EmpID = 6, EmpName = "E6"};

    List<Employee> employees = new List<Employee>();
    employees.Add(e1);
    employees.Add(e2);
    employees.Add(e3);
    employees.Add(e4);
    employees.Add(e5);
    employees.Add(e6);

    itemCount = employees.Count;

    //Get subset of employees based on paging and sorting parameters
    //Sorting can be based on EmpID or EmpName
    List<Employee> currentPageEmployees = null;
    return currentPageEmployees;
}

调用方法

        int count = 0;
        List<Employee> e = GetMyData(0, 2, out count, "EmpID", "descending");

Answer 1

您可以使用自定义选择器将 sortField 解析为 Employee 类型的适当属性。然后对于排序方向，我假设 sortDirection 是升序或降序 - 如果是，那么 bool 可能更好？

举个例子:

var selector = new Func<Employee, object>(e => e.GetType().GetProperty(sortField).GetValue(e, null));
var query = sortDirection.Equals("descending", StringComparison.OrdinalIgnoreCase)
                ? employees.OrderByDescending(selector)
                : employees.OrderBy(selector);

List<Employee> currentPageEmployees = query
    .Skip(pageIndex * pageSize)
    .Take(pageSize)
    .ToList();

有一些 Dynamic Linq 扩展可以使内容更易读。

编辑:移除类型转换