How to do CreateFileMapping in a C++ DLL and access it in C#, VB and C++

Imports System.Runtime.InteropServices

Public Class Form1
    Public Declare Unicode Sub SetValue Lib "sharedmem.dll" (ByVal key As String, _
                                                          ByVal value As String)

    Declare Unicode Function GetValue Lib "sharedmem.dll" (ByVal key As String) As IntPtr

    Declare Auto Function GetRecordCount Lib "sharedmem.dll" () As Integer


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        SetValue(TextBox1.Text, TextBox2.Text)
        LinkLabel1_LinkClicked(Nothing, Nothing)
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        TextBox2.Text = Marshal.PtrToStringUni(GetValue(TextBox1.Text))
    End Sub

    Private Sub LinkLabel1_LinkClicked(ByVal sender As System.Object, ByVal e As System.Windows.Forms.LinkLabelLinkClickedEventArgs) Handles LinkLabel1.LinkClicked
        LinkLabel1.Text = "Record Count = " + GetRecordCount().ToString()
    End Sub
End Class