将嵌套的 for 循环转换为单个 LINQ 语句 [英] Convert nested for-loops into single LINQ statement

问题描述

有人可以帮我把这个嵌套结构变成一个 LINQ 语句吗?

can someone please help me turn this nested structure into a single LINQ statement?

        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]);
                    }
                }
            }
        }

推荐答案

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):

Nested loops usually end up with multiple "from" clauses (which are converted into calls to SelectMany by the compiler):

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()代码>列表<T>.)

(That's assuming that remoteAccessLogs is empty before this call, and that you're happy iterating over it directly - you can call ToList() if you want a List<T>.)

这是点符号的形式:

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

或者列表:

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

请注意，我使用重载的 == 表示字符串，因为我发现它比调用 Equals 方法更容易阅读.两者都可以.

Note that I've used the overloaded == for string as I find it easier to read than calling the Equals method. Either will work though.

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