c# - 在 switch 语句中为 LINQ 创建 where 条件

Question

所以基本上我必须为 4 个不同的角色获得 4 个不同的员工列表。 List of Roles 是一个 List of Enum，如下所示:

public enum Roles {
       [Description("Level 1")]
       L1,

       [Description("Level 2")]
       L2,

       [Description("Level 3")]
       L3,

       [Description("Level 4")]
       L4
};

• L1可以查看L1、L2、L3和L4<
• L2可以查看L2、L3和L4
• L3可以查看L3和L4。
• L4 无权查看任何员工。

下面是我如何编写获取员工的查询。

if (!Equals(Role, Enum.GetName(typeof(GlobalMethods.Roles), 3)))
{
      var _role = (GlobalMethods.Roles)Enum.Parse(typeof(GlobalMethods.Roles), Role,true);
      List<EmployeeViewModel> employees = new List<EmployeeViewModel>();
      switch (_role)
      {
            case GlobalMethods.Roles.L1:
                 employees = context.tblEmployees.Where(x => x.EmpID != homeViewModel.UserViewModel.EmpID).ToList().Select(x => new EmployeeViewModel
                 {
                      EmpActive = x.EmpActive,
                      EmpDOB = x.EmpDOB,
                      EmpName = x.EmpName
                 }).ToList();
                 break;
            case GlobalMethods.Roles.L2:
                 employees= context.tblEmployees.Where(x => x.EmpID != homeViewModel.UserViewModel.EmpID).ToList().Where(x=>x.EmpRole != Enum.GetName(typeof(GlobalMethods.Roles), 0)).Select(x => new EmployeeViewModel
                 {
                      EmpActive = x.EmpActive,
                      EmpDOB = x.EmpDOB,
                      EmpName = x.EmpName,
                 }).ToList();
                 break;
            case GlobalMethods.Roles.L3:
                 employees = context.tblEmployees.Where(x => x.EmpID != homeViewModel.UserViewModel.EmpID).ToList().Where(x.EmpRole != Enum.GetName(typeof(GlobalMethods.Roles), 0) && x.EmpRole != Enum.GetName(typeof(GlobalMethods.Roles), 1)).Select(x => new EmployeeViewModel
                 {
                      EmpActive = x.EmpActive,
                      EmpDOB = x.EmpDOB,
                      EmpName = x.EmpName,
                 }).ToList();
                 break;
            default: break;
      }
}

所以在上面的代码中，我有相同的 LINQ 查询，但只有 where 条件不同。有什么方法可以准备动态 where 条件并一次性获取列表？

Answer 1

这应该有效。它假设每个 GlobalMethods.Roles 都可以查看具有更大 int 值的所有角色。情况就是这样，因为角色是您声明的规则。

if (!Equals(Role, Enum.GetName(typeof(GlobalMethods.Roles), 3)))
{
     var _role = (GlobalMethods.Roles)Enum.Parse(typeof(GlobalMethods.Roles), Role, true);
     List<EmployeeViewModel> employees = new List<EmployeeViewModel>();
     string[] viewableRoles = GetViewableRoles(_role);
     employees = context.tblEmployees
                .Where(x => x.EmpID != homeViewModel.UserViewModel.EmpID && viewableRoles.Contains(x.EmpRole))
                .Select(x => new EmployeeViewModel
                {
                    EmpActive = x.EmpActive,
                    EmpDOB = x.EmpDOB,
                    EmpName = x.EmpName
                }).ToList();
}

private string[] GetViewableRoles(GlobalMethods.Roles userRole)
{
    //Uncomment if L4 can actually view no roles, including itself.
    // /if (userRole == GlobalMethods.Roles.L4)
    // {
    //  return new string[0];
    // }

    IEnumerable<GlobalMethods.Roles> allRoles = Enum.GetValues(typeof(GlobalMethods.Roles)).Cast<GlobalMethods.Roles>();
    return (from role in allRoles 
                where (int)role >= (int)userRole 
                select role.ToString()).ToArray();
}