Question

I want to build my own flat file database. Here is how I access the flat file database

Dim fs As New System.IO.FileStream("C:\MyDb.txt", IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read)
Dim sr As New System.IO.StreamReader(fs)

Is there a limit imposed by .Net for the usage of System.IO.FileShare.Read, System.IO.FileShare.Write and System.IO.FileShare.ReadWrite when dealing with a file?

I mean is that .Net capable to support thousands of users using file stream and stream reader objects with System.IO.FileShare.Read to access a single file concurrently?

Answer 1

I don’t know the exact limit imposed by .NET/windows, so I have created a real test for you. I ran the following test code for few minutes and I found that up to 635908 counts of system.io.fileshare usage, it still functional, i.e. you can still read the flat database file’s content.

Here is the code (it is a winform application, .Net 4):

Public Class Form1

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim filepath As String = "c:\database.txt"

        Dim filestream As System.IO.FileStream

        Dim count As Int32

        For count = 0 To System.Int32.MaxValue
            filestream = New System.IO.FileStream(filepath, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read)
            AppendLog(count, filestream.ReadByte)
        Next
    End Sub

    Private LogFilepath As String = "C:\LogInfo.txt"
    Private Enter As String = Chr(13) & Chr(10)
    Private Space As String = " "

    Private Sub AppendLog(ByVal Sequence As Int32, ByVal info As Byte)
        System.IO.File.AppendAllText(LogFilepath, Enter & Sequence & Space & CStr(info))
    End Sub

End Class