Are multiple memory mapped files bugged?-CodePudding

when adding a second memory mapped file to my project the first one no longer works cross processes.

Imports System.IO.MemoryMappedFiles

Module IPC
    Private ReadOnly _QlCtxOpen As MemoryMappedViewAccessor = MemoryMappedFile.CreateOrOpen("IPC_QlCtxOpen", 1).CreateViewAccessor()
    Public Property IsQlCtxOpen As Boolean
         Get
            Dim value As Boolean = _QlCtxOpen.ReadBoolean(0)
            Debug.Print($"QlCtxOpen {value}")
            Return value
        End Get
        Set(ByVal value As Boolean)
            _QlCtxOpen.Write(0, value)
            Debug.Print($"set QlCtxOpen to {value}")
        End Set
    End Property
End Module

when adding following line to the module the first mmf still works in the same process but a second process will no longer be able to read the correct value.

Private ReadOnly _alreadyOpenPID As MemoryMappedViewAccessor = MemoryMappedFile.CreateOrOpen("IPC_alreadyOpenPID", 4).CreateViewAccessor()

I know i should use a mutex for writing but in my project the write is triggered by mouse action so only 1 process will use it at the same time.

I don't understand what i'm doing wrong to break the first mmf, it works w/o the second mmf.

I'm using Microsoft Visual Studio Community 2019 Version 16.11.11 .NET Framework 4.7.2

CodePudding user response：

Turns out garbage collection is the culprit here. To fix this behavior make sure to have a reference to the memory-mapped file for as long as you need the value to be read by other processes.

Why it still worked with only 1 declaration and no reference to the memory-mapped file is a mystery to me.