c# - 将嵌套的 for 循环转换为单个 LINQ 语句

Question

有人可以帮我把这个嵌套结构变成单个 LINQ 语句吗？

        EventLog[] logs = EventLog.GetEventLogs();
        for (int i = 0; i < logs.Length; i++)
        {
            if (logs[i].LogDisplayName.Equals("AAA"))
            {
                for (int j = 0; j < logs[i].Entries.Count; j++)
                {
                    if (logs[i].Entries[j].Source.Equals("BBB"))
                    {
                        remoteAccessLogs.Add(logs[i].Entries[j]);
                    }
                }
            }
        }

Answer 1

嵌套循环通常以多个“from”子句结束(编译器将其转换为对 SelectMany 的调用):

var remoteAccessLogs = from log in EventLogs.GetEventLogs()
                       where log.LogDisplayName == "AAA"
                       from entry in log.Entries
                       where entry.Source == "BBB"
                       select entry;

(假设 remoteAccessLogs 在此调用之前为空，并且您很乐意直接对其进行迭代 - 如果您想要 ToList()，可以调用 List<T>。)

这是点符号形式:

var remoteAccessLogs = EventLogs.GetEventLogs()
                                .Where(log => log.LogDisplayName == "AAA")
                                .SelectMany(log => log.Entries)
                                .Where(entry => entry.Source == "BBB");

或者对于列表:

var remoteAccessLogs = EventLogs.GetEventLogs()
                                .Where(log => log.LogDisplayName == "AAA")
                                .SelectMany(log => log.Entries)
                                .Where(entry => entry.Source == "BBB")
                                .ToList();

请注意，我对字符串使用了重载的 ==，因为我发现它比调用 Equals 更容易阅读。方法。不过，两者都可以。