Questions with the message log for the user

When sending a log to the user, the message appears with the line name along with the numeral, how can I separate and keep the message: Cell B for line 1 and / or cell C for line 1 must be filled.

However, the following log is displayed:

Cell B for line1 and / or cell C for line 1 must be filled. How could I be solving this? follow my code.

privatevoidPreliminaryVerification (IEnumerable data)
{
int i = 0;
bool imported = falso ;
foreach (var line in data)
{
i = i + 1;
// Valida se pelo menos uma das colunas NumProcess estiver preenchida
if (line.ItemArray [1] .ToString () == "" && line.ItemArray [2] .ToString () == "" )
{
// My problem here is that by showing the log, instead of showing line 1, it shows // line1. Could someone please help me?
log.Append ( "The B cell" + (i) + "and / or C cell" + (i) + "must be completed.
" );
fileInvalidated = true ;
}
}