使用循环时连接 LINQ 查询结果

Question

我需要对一堆文件进行循环并通过 LINQ 查询输出日志条目：

foreach (string file in Directory.EnumerateFiles(TextBoxLogDirectory.Text, "*.log"))
{
    FileStream stream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
    using (LogReader reader = new LogReader(stream))
    {
        var events = (from x in reader.Parse().Where(y => y.IsInRange(range) && (y.EventNo == 1180 || y.EventNo == 1187) && y.GetDefaultMessageField().Contains(":Outbound/"))
                      group x by x.GetDefaultMessageField() into grouping
                      select new
                      {
                          ID = grouping.Key,
                          Event1180 = grouping.LastOrDefault(z => z.EventNo == 1180),
                          Event1187 = grouping.LastOrDefault(z => z.EventNo == 1187)
                      }).ToList();
    }
}

此查询必须一次在单个文件上运行，以上工作正常，但我需要继续将查询结果附加到foreach 循环之外的对象。像这样的东西（虽然这不起作用，不幸的是）：

dynamic events; // I want to append to this object outside of the loop's scope.
foreach (string file in Directory.EnumerateFiles(TextBoxLogDirectory.Text, "*.log"))
{
    FileStream stream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
    using (LogReader reader = new LogReader(stream))
    {
        events = (from x in reader.Parse().Where(y => y.IsInRange(range) && (y.EventNo == 1180 || y.EventNo == 1187) && y.GetDefaultMessageField().Contains(":Outbound/"))
                      group x by x.GetDefaultMessageField() into grouping
                      select new
                      {
                          ID = grouping.Key,
                          Event1180 = grouping.LastOrDefault(z => z.EventNo == 1180),
                          Event1187 = grouping.LastOrDefault(z => z.EventNo == 1187)
                      }).ToList().Concat(events);
    }
}

我怎样才能实现这种行为？

不确定是否有帮助，我上面的查询将返回带有 (string)ID, (LogEvent)Event1180, and (LogEvent)Event1187. 的对象

Answer 1

你可以试试这样的：

Directory.EnumerateFiles(TextBoxLogDirectory.Text, "*.log")
         .SelectMany(ParseFile);

ParseFile 定义为

IEnumerable<string> ParseFile(string file)
{
    using (FileStream stream =
               new FileStream(file, FileMode.Open, FileAccess.Read,
                              FileShare.ReadWrite | FileShare.Delete))
    using (LogReader reader = new LogReader(stream))
    {
        return (from x in reader.Parse()
                   .Where(y => y.IsInRange(range) &&
                          (y.EventNo == 1180 || y.EventNo == 1187) &&
                          y.GetDefaultMessageField().Contains(":Outbound/"))
                group x by x.GetDefaultMessageField() into grouping
                select new
                {
                    ID = grouping.Key,
                    Event1180 = grouping.LastOrDefault(z => z.EventNo == 1180),
                    Event1187 = grouping.LastOrDefault(z => z.EventNo == 1187)
                }).ToList();
    }
}

如果您愿意，也可以内联辅助函数。

这会产生一个IEnumerable<string>，您或许应该立即使用ToList 实现它。

---

编辑：哦，我明白了，我们的类型不匹配。

有两种解决方法：您应该命名匿名类型并让函数返回 IEnumerable<that type>，或者只是将函数内容内联到 lambda：

Directory.EnumerateFiles(TextBoxLogDirectory.Text, "*.log")
         .SelectMany(file =>
    {
        using (FileStream stream =
                   new FileStream(file, FileMode.Open, FileAccess.Read,
                                  FileShare.ReadWrite | FileShare.Delete))
        using (LogReader reader = new LogReader(stream))
        {
            return (from x in reader.Parse()
            // ...
                }).ToList();
        }
    }
);