Imports System.Runtime.InteropServices
Imports System.IO
Imports System.Text

Module Module1

    Sub Main()

        Dim inputPath As String

        Console.Write("Specificare il percorso completo del file: ")
        inputPath = Console.ReadLine()

        Console.WriteLine("Il percorso:")
        Console.WriteLine(inputPath)
        Console.WriteLine("corrisponde a:")
        Console.WriteLine(FSHelper.ToShortPath(inputPath))
        Console.ReadLine()

    End Sub

    Public Class FSHelper

        <DllImport("kernel32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
        Public Shared Function GetShortPathName( _
            <MarshalAs(UnmanagedType.LPTStr)> ByVal path As String, _
            <MarshalAs(UnmanagedType.LPTStr)> ByVal shortPath As StringBuilder, _
            ByVal shortPathLength As Integer) As Integer
        End Function

        <DllImport("kernel32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
        Public Shared Function GetLongPathName( _
            <MarshalAs(UnmanagedType.LPTStr)> ByVal path As String, _
            <MarshalAs(UnmanagedType.LPTStr)> ByVal longPath As StringBuilder, _
            ByVal shortPathLength As Integer) As Integer
        End Function

        Public Shared Function ToLongPath(ByVal inPath As String) As String

            Dim sb As New StringBuilder(1024)
            Dim i As Integer = GetLongPathName(inPath, sb, sb.Capacity)
            'i = Marshal.GetLastWin32Error()
            Return sb.ToString()

        End Function

        Public Shared Function ToShortPath(ByVal inPath As String) As String

            Dim sb As New StringBuilder(1024)
            Dim i As Integer = GetShortPathName(inPath, sb, sb.Capacity)
            Return sb.ToString()

        End Function

    End Class

End Module

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.IO;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            String inputPath;

            Console.WriteLine("Specificare il percorso completo del file: ");
            inputPath = Console.ReadLine();

            Console.WriteLine("Il percorso:");
            Console.WriteLine(inputPath);
            Console.WriteLine("corrisponde a:");
            Console.WriteLine(FSHelper.ToShortPath(inputPath));
            Console.ReadLine();
        }
    }

    class FSHelper
    {
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern uint GetShortPathName(
           [MarshalAs(UnmanagedType.LPTStr)] string lpszLongPath,
           [MarshalAs(UnmanagedType.LPTStr)] StringBuilder lpszShortPath,
           uint cchBuffer);

        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern uint GetLongPathName(
            [MarshalAs(UnmanagedType.LPTStr)] string lpszShortPath,
            [MarshalAs(UnmanagedType.LPTStr), Out] StringBuilder lpszLongPath,
            uint cchBuffer);


        public static string ToLongPath(string shortName)
        {
            uint bufferSize = 256;
            StringBuilder longNameBuffer = new StringBuilder((int)bufferSize);

            uint result = GetLongPathName(shortName, longNameBuffer, bufferSize);

            return longNameBuffer.ToString();
        }


        public static string ToShortPath(string longName)
        {
            uint bufferSize = 256;
            StringBuilder shortNameBuffer = new StringBuilder((int)bufferSize);

            uint result = GetShortPathName(longName, shortNameBuffer, bufferSize);

            return shortNameBuffer.ToString();
        }
    
    }

}