如何用LINQ实现筛选：排除所有状态均属有效列表的ProcessId？

我有以下代码：

var validReasons = new List<string>{"CLOSE", "OPEN", "DEL", "ARCCHIVE", "HOLD", "REP"};
var processList = new List<ProcessItem>{
    new ProcessItem{ProcessId = 1, Status = "ARCCHIVE"}, 
    new ProcessItem{ProcessId = 1, Status = "ARCCHIVE"}, 
    new ProcessItem{ProcessId = 3, Status = "xx"}, 
    new ProcessItem{ProcessId = 3, Status = "xx"}, 
    new ProcessItem{ProcessId = 4, Status = "xx"}, 
    new ProcessItem{ProcessId = 5, Status = "xx"}, 
    new ProcessItem{ProcessId = 5, Status = "xx"}, 
    new ProcessItem{ProcessId = 6, Status = "CLOSE"},
    new ProcessItem{ProcessId = 6, Status = "CLOSE"}, 
    new ProcessItem{ProcessId = 6, Status = "xx"}};


var data = processList.GroupBy(p => p.ProcessId).Where(g => g.All(item => !validReasons.Contains(item.Status))).SelectMany(g => g).ToList();

foreach (var item in data)
{
    Console.WriteLine($"ProcessId: {item.ProcessId}, Status: {item.Status}");
}

当前输出为：

ProcessId: 3, Status: xx
ProcessId: 3, Status: xx
ProcessId: 4, Status: xx
ProcessId: 5, Status: xx
ProcessId: 5, Status: xx

但我需要显示ProcessId为6的记录（因其并非所有状态都在validReasons列表中），期望输出应为：

ProcessId: 3, Status: xx
ProcessId: 3, Status: xx
ProcessId: 4, Status: xx
ProcessId: 5, Status: xx
ProcessId: 5, Status: xx
ProcessId: 6, Status: CLOSE
ProcessId: 6, Status: CLOSE
ProcessId: 6, Status: xx

请问能否用LINQ实现该需求？

可以实现，只需修改LINQ中的筛选条件：

原代码的Where条件g.All(item => !validReasons.Contains(item.Status))表示组内所有项的Status都不在validReasons中，这会排除ProcessId=6的组（因为该组存在Status为CLOSE的项，属于validReasons）。

我们需要的是组内存在至少一个项的Status不在validReasons中，或者等价于组内不是所有项的Status都在validReasons中，对应两种写法：

写法一：使用Any判断存在不符合的项 #

var data = processList.GroupBy(p => p.ProcessId)
                      .Where(g => g.Any(item => !validReasons.Contains(item.Status)))
                      .SelectMany(g => g)
                      .ToList();

写法二：取反All判断（逻辑等价） #

var data = processList.GroupBy(p => p.ProcessId)
                      .Where(g => !g.All(item => validReasons.Contains(item.Status)))
                      .SelectMany(g => g)
                      .ToList();

修改后执行代码，就能得到你期望的输出：保留所有组内存在非valid状态项的完整组数据，包括ProcessId=6的所有记录。

内容的提问来源于stack exchange，提问作者causita