聚合结果时并行LINQ UnauthorizedAccessException

Question

我正在使用LINQ并行搜索以查找模式匹配文件。

public class ParallelLinq
{
    public IList<string> SearchFolders = new List<string>
    {
        @"C:\Windows" //can be multiple
    };

    protected virtual IEnumerable<string> GetFiles(string path, string[] searchPatterns, SearchOption searchOption = SearchOption.AllDirectories)
    {
        return searchPatterns.AsParallel()
            .SelectMany(searchPattern =>
            {
                try
                {
                    return Directory.EnumerateFiles(path, searchPattern, searchOption);
                }
                catch (Exception ex) //catch UnauthoizedException/IOExceptions
                {
                    return Enumerable.Empty<string>();
                }
            });
    }

    public IEnumerable<string> Find(IList<string> patterns)
    {
        var testResultFiles = Enumerable.Empty<string>();

        if (!SearchFolders.Any() || !patterns.Any())
        {
            return testResultFiles;
        }

        testResultFiles = SearchFolders.AsParallel().Aggregate(testResultFiles, (current, folder) => current.Union(GetFiles(folder, patterns.ToArray())));

        return testResultFiles;
    }
}

但是当我尝试评估我在System.UnauthorizedAccessException: Access to the path 'C:\Windows\appcompat\Programs' is denied.中运行的值时

var plinq = new ParallelLinq();
var res = plinq.Find(new List<string> { "*.dll" });
Console.WriteLine("Linq Count: " + res.Count());

虽然预计会有这些例外情况，但我们如何抓住它们并继续前进？

完全例外：

未处理的异常：System.AggregateException：发生一个或多个错误。 ---> System.UnauthorizedAccessException：拒绝访问路径'C：\ Windows \ appcompat \ Programs'。在System.IO .__ Error.WinIOError（Int32 errorCode，String maybeFullPath） 在System.IO.FileSystemEnumerableIterator

1.AddSearchableDirsToStack(SearchData
  localSearchData)    at
  System.IO.FileSystemEnumerableIterator

1.MoveNext（）处于System.Linq.Parallel.SelectManyQueryOperator3.SelectManyQueryOperatorEnumerator1.MoveNext（在System.Linq.Parallel.QueryTask的System.Linq.Parallel.SpoolingTaskBase.Work（）中的TOutput＆currentElement，Pair

2& currentKey)    at
  System.Linq.Parallel.PipelineSpoolingTask

2.SpoolingWork（）。 System.Linq.Parallel.QueryTask中的BaseWork（Object unused）。<> c。 System__Threading.Tasks.Task.Execute（）中System.Threading.Tasks.Task.InnerInvoke（）的b__10_0（Object o）---内部异常堆栈跟踪结束---在System.Linq.Parallel.QueryTaskGroupState。 System.Linq.Parallel.AsynchronousChannelMergeEnumerator中的QueryEnd（Boolean userInitiatedDispose）

1.MoveNextSlowPath()
  at
  System.Linq.Parallel.AsynchronousChannelMergeEnumerator

1.MoveNext（） System.Linq.Enumerable.Count [TSource]上的System.Linq.Parallel.QueryOpeningEnumerator

1.MoveNext()    at
  System.Linq.Enumerable.<UnionIterator>d__67

1.MoveNext（）处理（IEnumerable`1 source）

Answer 1

public class ParallelLinq
{
    public IList<string> SearchFolders = new List<string>
    {
        @"C:\Windows" //can be multiple
    };

    private static string[] TryGetTopDirectories(string path)
    {
        try
        {
            return Directory.GetDirectories(path, "*", SearchOption.TopDirectoryOnly);
        }
        catch
        {
            return new string[0];
        }
    }

    private static IEnumerable<string> GetSubfolders(string path, SearchOption searchOption)
    {
        if (searchOption == SearchOption.TopDirectoryOnly)
        {
            return TryGetTopDirectories(path);
        }
        else
        {
            var topFolders = TryGetTopDirectories(path);
            return topFolders.Concat(
                topFolders.SelectMany(subFolder => GetSubfolders(subFolder, searchOption)));
        }
    }

    protected virtual ParallelQuery<string> GetFiles(string path, string[] searchPatterns, SearchOption searchOption = SearchOption.AllDirectories)
    {
        return GetSubfolders(path, searchOption).AsParallel()
            .SelectMany(subfolder =>
            {
                try
                {
                    return searchPatterns.SelectMany(searchPattern => Directory.EnumerateFiles(subfolder, searchPattern)).ToArray();
                }
                catch (Exception ex) //catch UnauthoizedException/IOExceptions
                {
                    return Enumerable.Empty<string>();
                }
            });
    }

    public IEnumerable<string> Find(IList<string> patterns)
    {
        var testResultFiles = Enumerable.Empty<string>();

        if (!SearchFolders.Any() || !patterns.Any())
        {
            return testResultFiles;
        }

        testResultFiles = SearchFolders.AsParallel().Aggregate(testResultFiles, (current, folder) => current.Union(GetFiles(folder, patterns.ToArray())));

        return testResultFiles;
    }
}

Answer 2

似乎路径'C：\ Windows \ appcompat \ Programs'阻止程序创建文件。可以通过在文件夹本身中添加额外权限来解决此问题。

How to add permission to folder manually