>>In the database the column is smallint and defined as short in the class definition.
>
>So why is the Convert.ToInt16 needed?

I think it's not needed, I'll remove it. In my original code it was needed as the result was anonymous type.

So, the code now is reduced to

var lastLocSuffix = _salespointAdapter.GetAll().Max(sp=>sp.LocSuffix);
            Int16 newSuffix = 1;
            if (lastLocSuffix != null)
            {
                newSuffix = lastLocSuffix++;                
            }

            salespoint.LocSuffix = newSuffix;