InfoPath Dev

I have a browser-enabled form that works in InfoPath and fails with System.IndexOutOfRangeException: Index was outside the bounds of the array.

\FormCode.cs:line 36 
at Microsoft.Office.InfoPath.Server.SolutionLifetime.XmlEventExternal.<>c__DisplayClass10.<>c__DisplayClass12.b__b() 
at Microsoft.Office.InfoPath.Server.Util.DocumentReliability.InvokeBusinessLogic(Thunk thunk) 
at Microsoft.Office.InfoPath.Server.SolutionLifetime.XmlEventExternal.<>c__DisplayClass10.b__a(Object sender, XmlEventArgs e) 
at Microsoft.Office.InfoPath.Server.SolutionLifetime.XmlEventExternal.<>c__DisplayClass20.b__1c() 
at Microsoft.Office.InfoPath.Server.DocumentLifetime.OMExceptionManager.CallFormCodeWithExceptionHandling(UserMessages userMessages, OMCall d)

The line 36 containing CreateNavigator() was indicated in the exception message in the browser. Why? Is there any discrepancy between line numbering in the source code/dll?

I think the error might arise from the line with if(...Split()[1]) but the indication is misleading. Any ideas?

the code goes like this:

public void Recepients_Changed(object sender, XmlEventArgs e)
        {
            XPathNavigator n = this.CreateNavigator(); //same as this.MainDataSource.CreateNavigator();
            
            switch (e.Operation)
            { 
                case XmlOperation.Delete:
                case XmlOperation.ValueChange:
                case XmlOperation.Insert:
                    n.SelectSingleNode("/my:FormRoot/my:RecepientsCount", NamespaceManager)
                        .SetValue(string.Empty);
                    n.SelectSingleNode("/my:FormRoot/my:RecepientsList", NamespaceManager)
                        .SetValue(string.Empty);
                    n.SelectSingleNode("/my:FormRoot/my:RecepientsCount", NamespaceManager)
                        .SetValue(
                            n.Select("/my:FormRoot/my:Recepients/my:Person", NamespaceManager)
                                .Count.ToString()
                        );
                    XPathNodeIterator i = n.Select("/my:FormRoot/my:Recepients/my:Person", NamespaceManager);
                    while (i.MoveNext())
                    {
                        if (
                        DataSources["Recepients"].CreateNavigator()
                            .SelectSingleNode("//dfs:Recepients[@Person='"+
                            i.Current.SelectSingleNode("my:AccountId",NamespaceManager)
                                .Value.Split(@"\".ToCharArray()[0])[1]
                            +"']", NamespaceManager) != null
                            ) 
                        { 
                        
                        n.SelectSingleNode("/my:FormRoot/my:RecepientsList", NamespaceManager)
                            .SetValue(
                                (n.SelectSingleNode("/my:FormRoot/my:Recepients/my:Person/my:AccountType", NamespaceManager)
                                    .Value=="User")
                                ? n.SelectSingleNode("/my:FormRoot/my:RecepientsList", NamespaceManager).Value + i.Current
                                    .SelectSingleNode("my:DisplayName", NamespaceManager)
                                        .Value+"; "
                                : string.Empty
                            );
                        }
                    }
                    break;
                default: break;
            }
            
        }

thanks in advance

I have found that the culprit is in the string.Split(char) method. The exception is thrown (but doesn't cancel the actual splitting) if you uncomment the Split part in the following simple sequence:

string login = i.Current.SelectSingleNode("my:AccountId", NamespaceManager).Value/*.Split('\\')[1]*/;
n.SelectSingleNode("/my:FormRoot/my:RecepientsList", NamespaceManager).SetValue(login);

This works:

string login = i.Current.SelectSingleNode("my:AccountId", NamespaceManager)
.Value/*.Split('\\')[1]*/;
login = login.Substring(login.IndexOf('\\')+1);
n.SelectSingleNode("/my:FormRoot/my:RecepientsList", NamespaceManager).SetValue( login );