Getting All Users in a Computer

First we'll create a class to process WinApi calls.

This Class has been written by  Michael Bright in 2003.Since then i've been using this code and extending it for network related needs.

using System;

using System.Runtime.InteropServices;

namespace GettingAllUsers

{

 

public class NetworkAPI

{

 

// USER_INFO_1 - Strucutre to hold obtained user information

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]

public struct USER_INFO_1

{

public string usri1_name;

public string usri1_password;

public int usri1_password_age;

public int usri1_priv;

public string usri1_home_dir;

public string comment;

public int usri1_flags;

public string usri1_script_path;

}

 

// USER_INFO_0 - Structure to hold Just Usernames

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]

public struct USER_INFO_0

{

public String Username;

}

 

// NetUserAdd - To Add Users to a local machine or Network

[DllImport("Netapi32.dll")]

public extern static int NetUserAdd([MarshalAs(UnmanagedType.LPWStr)] string servername, int level, ref USER_INFO_1 buf, int parm_err);

 

// NetUserDel - To delete Users from a local machine or Network

[DllImport("Netapi32.dll")]

public extern static int NetUserDel([MarshalAs(UnmanagedType.LPWStr)] string servername, [MarshalAs(UnmanagedType.LPWStr)] string username);

 

// NetUserGetInfo - Returns to a struct Information about the specified user

[DllImport("Netapi32.dll")]

public extern static int NetUserGetInfo([MarshalAs(UnmanagedType.LPWStr)] string servername,[MarshalAs(UnmanagedType.LPWStr)] string username,int level,out IntPtr bufptr);

 

// NetUserSetInfo - Allows us to modify User information

[DllImport("Netapi32.dll")]

public extern static int NetUserSetInfo([MarshalAs(UnmanagedType.LPWStr)] string servername,[MarshalAs(UnmanagedType.LPWStr)] string username,int level,ref USER_INFO_1 buf, int error);

 

// NetUserChangePassword - Allows us to change a users password providing we have it

[DllImport("Netapi32.dll")]

public extern static int NetUserChangePassword([MarshalAs(UnmanagedType.LPWStr)] string domainname,[MarshalAs(UnmanagedType.LPWStr)] string username,[MarshalAs(UnmanagedType.LPWStr)] string oldpassword,[MarshalAs(UnmanagedType.LPWStr)] string newpassword);

 

// NetUserEnum - Obtains a list of all users on local machine or network

[DllImport("Netapi32.dll")]

public extern static int NetUserEnum(string servername, int level, int filter, out IntPtr bufptr, int prefmaxlen, out int entriesread, out int totalentries, out int resume_handle);

 

// NetAPIBufferFree - Used to clear the Network buffer after NetUserEnum

[DllImport("Netapi32.dll")]

public extern static int NetApiBufferFree(IntPtr Buffer);

 

public NetworkAPI()

{

//

// TODO: Add constructor logic here

//

}

}

}

Add a ListBox in your form and then,Later inside your main application create a function:

public void EnumerateUsers()

{

int EntriesRead;

int TotalEntries;

int Resume;

listBox1.Items.Clear();

 

IntPtr bufPtr;

 

NetworkAPI.NetUserEnum(null, 0, 2, out bufPtr, -1, out EntriesRead, out TotalEntries, out Resume);

 

if (EntriesRead > 0)

{

NetworkAPI.USER_INFO_0[] Users = new NetworkAPI.USER_INFO_0[EntriesRead];

IntPtr iter = bufPtr;

for (int i = 0; i < EntriesRead; i++)

{

Users[i] = (NetworkAPI.USER_INFO_0)Marshal.PtrToStructure(iter, typeof(NetworkAPI.USER_INFO_0));

iter = (IntPtr)((int)iter + Marshal.SizeOf(typeof(NetworkAPI.USER_INFO_0)));

listBox1.Items.Add(Users[i].Username);

 

}

NetworkAPI.NetApiBufferFree(bufPtr);

}

listBox1.SelectedIndex = 0;

 

 

}

Now just call EnumerateUsers inside Form_Load to populate them in your listbox at startup

private void Form1_Load(object sender, EventArgs e)

{

EnumerateUsers();

}

And run it! Hope that helps!