Assuming you won't be closing the Login form - just hiding it - then I'd change tmpfile from a private instance field to an internal static field. Form2 should then be able to access it without needing a reference to the Login form (Login.tmpfile or whatever it is).

On the second point, is it something like this that you're looking for ?

string path = "V:\\";
string[] tmpFiles = Directory.GetFiles(path, "*.tmp");
for (int i = 0; i < tmpFiles.Length; i++)
{
    tmpFiles[i] = Path.GetFileNameWithoutExtension(tmpFiles[i]).ToLower();
}
List<string> foundFiles = new List<string>();
for (int i = 0; i < comboBox1.Items.Count; i++)
{
    string fileName = comboBox1.Items[i].ToString();
    for (int j = 0; j < tmpFiles.Length; j++)
    {
        if (fileName.ToLower() == tmpFiles[j])  foundFiles.Add(fileName);
    }
}
if (foundFiles.Count == 0)
{
    MessageBox.Show("No matches were found");
}
else
{
    MessageBox.Show("The following matches were found: \r\n\r\n" + String.Join("\r\n", foundFiles.ToArray()));
}

OK, if you're closing the Login form, then I'd leave the tmpfile declaration as it is but add an internal instance field to Form2:

internal string tmpfile = "";

// something like this
Form2 f2 = new Form2();
f2.tmpfile = this.tmpfile;
f2.Show();
this.Close();

private Login_Load(object sender, EventArgs e)
{  
   string[] tmpFiles = Directory.GetFiles(Form1.Path.logpath , "*.tmp");
   for (int i = 0; i < tmpFiles.Length; i++)
   {
      tmpFiles[i] = Path.GetFileNameWithoutExtension(tmpFiles[i]).ToLower();
   }

   for (int i = 0; i < comboBox1.Items.Count; i++)
   {
      string fileName = comboBox1.Items[i].ToString();
      for (int j = 0; j < tmpFiles.Length; j++)
      {
         if (fileName.ToLower() == tmpFiles[j])
         {
            MessageBox.Show(String.Format("Another user ({0}) is already online, please wait", fileName));
            this.Close();
            return; 
         }
      }
   }      
}

just out of curiosity, is this a better (more efficient or more standard) than just passing the variable/object to the form in the form load event?

ie

Form2 frm = new Form2(tmpfiles);


then on form2

Private Form2(string[] tmpfiles)
{
//...
}

Got the Prob in line ......
string fileName = comboBox1.Items[i].ToString();

value of fileName is "System.Data.DataRowView" .............

So when we're trying to compare if (fileName.ToLower() == tmpFiles[j])... then the answer is never true bcoz the value of fileName is coming wrong.

I think this is bcoz comboBox.Items is being fetched from an Access files's Table by using OleDB thing like this:

OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;" + filename + ";Jet OLEDB:Database Password=pASSord");
            conn.Open();
            var comm = new OleDbCommand("SELECT users FROM [user]", conn);
            var adapter = new OleDbDataAdapter(comm);
            DataSet DS = new DataSet();
            adapter.Fill(DS, "user");
            comboBox1.DataSource = DS.Tables[0];
            comboBox1.DisplayMember = "users";
            comboBox1.ValueMember = "users";

Hmm, I think I can see now what the problem is :)

When you bind to a DataTable, a DataRowView is created behind the scenes to represent each item in the combobox. This DataRowView contains the column to be displayed.

So try replacing:

string fileName = comboBox1.Items[i].ToString();

DataRowView drv = (DataRowView)comboBox1.Items[i];
string fileName = drv["users"].ToString();

Bullseye Maaaaaan!!!!!!!!

Thx a millions for this help. U helped me create a wonderful feature.

But now the only prob is that sometimes while closing the form.... the utility is not able to delete the tmpfile automatically bcoz it get's a warning that the file is being used by another user. I can add a try block for this one... but I'm thinking that I should call the value of tmpfile in main form (form1) also and then try to delete it. Just to make sure that the .tmp is removed so that another user can log in.

But to fetch the username in Form1.... I think I have to call the value of below code in form1.

.
DataRowView drv = (DataRowView)comboBox1.Items[i];
string fileName = drv["users"].ToString();

Okie letme try to recreate the flow diagram:
There are three forms, Form1, LoginForm, and Editables.

Well, I'm clearer than I was ;)

So, let me just go through it in my simple-minded way which sometimes helps.

Suppose the application is being run on the network for the very first time and so there are no *.tmp files on the shared drive.

User1 then logs in and user1.tmp is created. He then logs out and the FormClosing eventhandler on the Editables form ensures that user1.tmp is deleted.

After that user2 logs in and user2.tmp is created. However, whilst user2 is still working on the application user1 tries to log in again but is told to wait because user2.tmp still exists.

So, if I've understood it correctly, it shouldn't be possible for more than one *.tmp file to exist at an given moment.

Now, it can be difficult to debug this sort of scheme because, if an uncaught exception is thrown and the application bombs out then, when you restart it, a user may still appear to be logged in (because his .tmp file wasn't deleted) when in fact he isn't!

Similar problems can arise if there's a power cut or if the user turns off his machine without shutting down the application first.

So, is it possible that you could be experiencing this sort of problem here?

.

:( Yup... u're right.

I had seen that same thing when I was trying to play around with creating & deleting the username.tmp file! Bcoz as the application is not able to find the username.tmp ( value of fileName is "System.Data.DataRowView") ... due to this reason the username.tmp file is existing in the drive.

To take care of these things I shall be deleting (*.tmp) files from the disk on Form1 closing event, or shall I delete (*.tmp) file when the file delete event (in logout) fails?

What do u say?

I'd put the code to ensure the .tmp file is deleted in Form1's FormClosed eventhandler.

It might also be a good idea to allow for the possibility that an unhandled exception may occur and shutdown the application before you can delete the file. You can do this by making the following changes to your program.cs file:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using System.Threading; // add this using directive

namespace WindowsFormsApplication1 // or whatever it's called
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            // add these  next two lines
            Application.ThreadException += Program_UIThreadException;
            Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);

            Application.Run(new Form1());
        }

        // add this handler
        static void Program_UIThreadException(object sender, ThreadExceptionEventArgs t)
        {
            MessageBox.Show("An unhandled exception has occurred. Application will be shut down");
            Application.Exit(); // closes all open forms and then application
        }
    }
}