MemoryMappedFile：无法找到指定的文件

Question

我无法使 MemoryMappedFile 模式正常工作。我有一个包含 25 excel 个电子表格的目录，我想使用 MemoryMappedFile 加载这些电子表格。 MemoryMappedFile.CreateFromFile 工作正常，但是当我调用 MemoryMappedFile.OpenExisting(lender) 时，它会读取前 3 个文件，然后在第 4 次尝试时，失败并出现异常：

Unable to find the specified file.

public static void Main()
{
    var files = System.IO.Directory.EnumerateFiles(@"lendersheets", "*.xls*").ToList();
    foreach (var file in files)
    {
        var lender = System.IO.Path.GetFileNameWithoutExtension(file);

        MemoryMappedFile.CreateFromFile(file, FileMode.Open, lender);
    }

    foreach (var file in files)
    {
        var lender = System.IO.Path.GetFileNameWithoutExtension(file);

        using (var mmfExisting = MemoryMappedFile.OpenExisting(lender))
        {
            var stream = mmfExisting.CreateViewStream();
            if (stream.CanRead && stream.CanWrite)
            {
                LoadFromStream(stream);
            }
        }                              
    }
}

更新:

我注意到当我删除 LoadFromStream 方法调用时，异常不再发生。这是 LoadFromStream 的逻辑：

    private static object LoadFromStream(Stream stream)
    {
        hssfwb = new HSSFWorkbook(stream);
        evaluator = new HSSFFormulaEvaluator(hssfwb);

        return hssfwb;
    }

Answer 1

我最终做了以下事情。我有一个内存中所有文件集合的单例实例。当我需要使用内存中的特定文件进行计算时，我会创建一个新的内存流实例：

private static readonly Dictionary<string, MemoryStream> _lenderPolicyFileStreams = new Dictionary<string, MemoryStream>();

        private static void CreateLenderPolicyFileStreams()
        {
            string appDataPath = HostingEnvironment.MapPath("~/App_Data");
            var files = Directory.EnumerateFiles(appDataPath, "*.xls*").ToList();

            foreach (var file in files)
            {
                var lenderName = Path.GetFileNameWithoutExtension(file);

                // Create a file stream
                var bytes = File.ReadAllBytes(file);
                var stream = new MemoryStream(bytes);

                // Add file stream to singleton collection
                if (lenderName != null) 
                    _lenderPolicyFileStreams.Add(lenderName, stream);
            }
        }

        public static Stream GetMemoryStreamByLenderName(string lender)
        {
            MemoryStream fetchedStream;
            _lenderPolicyFileStreams.TryGetValue(lender, out fetchedStream);

            if (fetchedStream == null)
                throw new Exception("Cannot find specified file stream by lender name");

            var clone = CloneStream(fetchedStream);
            return clone;
        }

        private static MemoryStream CloneStream(MemoryStream fileStream)
        {
            var memoryStream = new MemoryStream();

            fileStream.Position = 0;
            fileStream.CopyTo(memoryStream);
            memoryStream.Position = 0;

            return memoryStream;
        }

MemoryMappedFile：无法找到指定的文件

MemoryMappedFile: Unable to find the specified file

c#

memory-mapped-files