c#.net Error Looping throgh an Enumerator

Question

I have created a .bat file that displays a servers terminal Service SessionID and Username. Im Displaying the Information in a datagrid

Here is the output of the .bat file:

C:\Documents and Settings\adcock>qwinsta /server:ilsap01
 SESSIONNAME       USERNAME                 ID  STATE   TYPE        DEVICE
 console                                     0  Conn    wdcon
 rdp-tcp                                 65536  Listen  rdpwd
                   Jrodriguez               27  Disc    rdpwd
                   pbahena                   8  Disc    rdpwd
                   tfurr                     3  Disc    rdpwd
 rdp-tcp#2187      kchild                   14  Active  rdpwd
                   Trhodes                  10  Disc    rdpwd
                   ajordan                  16  Disc    rdpwd
                   Trhodes                  11  Disc    rdpwd
 rdp-tcp#2191      rluna                    15  Active  rdpwd
 rdp-tcp#2192      lcathey                  17  Active  rdpwd

---

the only information i want to display is the SessionID and Username that works somewhat with the code below.

protected void Button1_Click(object sender, EventArgs e)
{
    System.Diagnostics.ProcessStartInfo psi = new      System.Diagnostics.ProcessStartInfo(@"C:\listfiles.bat");
    psi.RedirectStandardOutput = true;
    psi.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
    psi.UseShellExecute = false;
    System.Diagnostics.Process listFiles;
    listFiles = System.Diagnostics.Process.Start(psi);
    System.IO.StreamReader rawUserData = listFiles.StandardOutput;
    listFiles.WaitForExit(30000);
    try
    {

        DataTable table2 = new DataTable();
        table2.Columns.Add(new DataColumn("UserName", typeof(string)));
        table2.Columns.Add(new DataColumn("SessionId", typeof(string)));

        String myString = rawUserData.ReadToEnd();
        string exp = @"([\w_]+)"; ;


        MatchCollection matches = Regex.Matches(myString, exp,RegexOptions.IgnoreCase);

        IEnumerator en = matches.GetEnumerator();

        while (en.MoveNext())
        {
            Match match = (Match)en.Current;

            if (en.Current.ToString() == "rdpwd")
            {
                en.MoveNext();

                Match match_Item = (Match)en.Current;

                string item = match_Item.Value;

                en.MoveNext();

                Match match_Item2 = (Match)en.Current;

                string item2 = match_Item2.Value;

                DataRow row = table2.NewRow();
                row[0] = item.Split()[0];
                row[1] = item2.Split()[0];
                //row[1] = item.Split(',')[1];
                table2.Rows.Add(row);

                //en.MoveNext();
                //break;

            }


        }

        this.displayUsers.DataSource = table2;
        this.displayUsers.DataBind();
    }

    catch (Exception ex)
    {
        Response.Write(ex);
    }

The Error i get is: Enumeration has either not started or has already finished.

I set a break point and it seams that the while loop completes but starts over and after it adds a couple duplicate records it throws the error. any ideas on whats be causing this. Im thinking its my RegEx

Answer 1

You are calling MoveNext twice inside the loop. That is causing the problem.

When you are in the last row, you call MoveNext, the it finds "rdpwd", then it calls MoveNext one time, then it calls it again, and this is when the enumerator becomes invalid. In then last MoveNext in the while it breaks because it's already at the end.