Opening a Memory Mapped File causes FileNotFoundException when deployed in IIS

user_226241 0
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Following the code example from this website, I created a windows console application that creates a mapped memory file:

        using (var file = MemoryMappedFile.CreateNew("myFile", 24))
        {
            var bytes = new byte[24];
            for (var i = 0; i < bytes.Length; i++)
                bytes[i] = (byte)(65 + i);

            using (var writer = file.CreateViewAccessor(0, bytes.Length))
            {
                writer.WriteArray<byte>(0, bytes, 0, bytes.Length);
            }
            Console.WriteLine("Run memory mapped file reader before exit");
            Console.WriteLine("Press any key to exit ...");
            Console.ReadLine();
        }

in a new asp.net web application I read the MMF using the code:

 protected void Page_Load(object sender, EventArgs e)
    {
        string sOutput = "";

        using (var file = MemoryMappedFile.OpenExisting("myFile"))
        {
            using (var reader = file.CreateViewAccessor(0, 24))
            {
                var bytes = new byte[24];
                reader.ReadArray<byte>(0, bytes, 0, bytes.Length);

                for (var i = 0; i < bytes.Length; i++)
                    sOutput += (char)bytes[i] + " ";

            }
        }

        Response.Write(sOutput);
    }

In the development IIS Express the file is read as expected and the page displays the data from the mapped memory file.

However, When deployed to IIS I get the exception System.IO.FileNotFoundException at the locationMemoryMappedFile.OpenExisting("myFile")

I tried changing the app pool identity to the same as the one running the MMF console application but this does didn't work.

memory-mapped-files ipc iis asp.net .net
3 Answers

For non physical file, there are two cases,

  1. File is deleted after your process exits.
  2. IIS does not run in same user as your console process, IIS runs in little restricted mode, so unless you create File with added security to allow process to access your service.

You will have to use http://msdn.microsoft.com/en-us/library/dd267529(v=vs.110).aspx this constructor with following security.

        MemoryMappedFileSecurity mSec = new MemoryMappedFileSecurity ();
        mSec.AddAccessRule(new AccessRule<MemoryMappedFileRights>(new SecurityIdentifier(WellKnownSidType.WorldSid, null),
            MemoryMappedFileRights .FullControl, AccessControlType.Allow));

And then try to access it from IIS with same security.

user_855970
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