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Summary

The CommandLineToArgvW API

C# Signature:

[DllImport("shell32.dll")]
static extern IntPtr CommandLineToArgvW(
   [MarshalAs(UnmanagedType.LPWStr)] string lpCmdLine, out int pNumArgs);

VB.NET Signature:

Declare Function CommandLineToArgv Lib "shell32.dll" Alias "CommandLineToArgvW" ( _
    ByVal lpCmdLine As String, _
    ByRef pNumArgs As Integer) As Long

User-Defined Types:

None.

Notes:

Minimum DLL Version	Shell32.dll version 6.0 or later
Minimum operating systems	Windows NT Workstation 3.5, Windows NT Server 3.5, Windows 2000 Professional, Windows 2000 Server, Windows XP, Windows Server 2003
Unicode	This function is implemented as Unicode.

Tips & Tricks:

Please add some!

Sample Code:

using System;
using System.Runtime.InteropServices;
using System.Text;

namespace CmdLineToArgvW
{
    class MainModule
    {
        static void Main(string[] args)
        {
            Console.WriteLine( "args.Length: {0}", args.Length );
            for ( int i = 0; i < args.Length; i++ )
            {
                Console.WriteLine( "args[{0}]={1}", i, args[i] );
            }

            Console.WriteLine();

            int argc;
            IntPtr argvPtr = IntPtr.Zero;
            try
            {
                argvPtr = CommandLineToArgvW( Environment.CommandLine, out argc );
                // CommandLineToArgvW will list the executable as argv[0].
                // I want to see the same count as you get from "string[] args".
                Console.WriteLine( "argc: {0}", argc - 1 );

                // argvPtr is a pointer to a pointer; dereference it
                IntPtr argPtr = Marshal.ReadIntPtr( argvPtr );

                for ( int i = 0; i < argc; i++ )
                {
                    string arg = Marshal.PtrToStringUni( argPtr );

                    // CommandLineToArgvW will list the executable as argv[0].
                    // I want to get the same output that "string[] args" yields,
                    // so I'll skip the output for i = 0
                    if ( i > 0 )
                    {
                        Console.WriteLine( "argv[{0}]={1}", i - 1, arg );
                    }

                    // Increment the pointer address by the number of Unicode bytes
                    // plus one Unicode character for the string's null terminator
                    int unicodeByteCount =
                        Encoding.Unicode.GetByteCount( arg ) +
                        Encoding.Unicode.GetByteCount( new char[] { Char.MinValue } );
                    argPtr = new IntPtr( argPtr.ToInt32() + unicodeByteCount );
                }

            }
            finally
            {
                LocalFree( argvPtr );
            }

        }

        // Here's an wrapper to CommandLineToArgvW I found useful (csells@sellsbrothers.com)
        public static IEnumerable<string> CommandLineToExeAndArgs() {
            return CommandLineToExeAndArgs(Environment.CommandLine);
        }

        public static IEnumerable<string> CommandLineToExeAndArgs(string cmdline) {
            List<string> args = new List<string>();
            IntPtr argvPtr = IntPtr.Zero;

            try {
                int argc;
                argvPtr = CommandLineToArgvW(cmdline, out argc);

                // argvPtr is a pointer to a pointer; dereference it
                IntPtr argPtr = Marshal.ReadIntPtr(argvPtr);

                // CommandLineToArgvW will list the executable as argv[0], so skip it
                for( int i = 0; i < argc; i++ ) {
                    string arg = Marshal.PtrToStringUni(argPtr);
                    args.Add(arg);

                    // Increment the pointer address by the number of Unicode bytes
                    // plus one Unicode character for the string's null terminator
                    int unicodeByteCount = Encoding.Unicode.GetByteCount(arg) + Encoding.Unicode.GetByteCount(new char[] { Char.MinValue });
                    argPtr = new IntPtr(argPtr.ToInt32() + unicodeByteCount);
                }
            }
            finally {
                LocalFree(argvPtr);
            }

            return args.ToArray();
        }

        [DllImport("shell32.dll")]
        static extern IntPtr CommandLineToArgvW(
            [MarshalAs(UnmanagedType.LPWStr)] string lpCmdLine,
            out int pNumArgs);

        [DllImport("kernel32.dll")]
        static extern IntPtr LocalFree(IntPtr hMem);
    }
}

Alternative Managed API:

Do you know one? Please contribute it!

Documentation

CommandLineToArgvW on MSDN