Uppercase with null check
    
        Converts a string to upper-case but checks for null strings first
    
    Source
    
        public static String ToUpperCheckForNull(this string input)
{
    string retval = input;
    if (!String.IsNullOrEmpty(retval))
    {
        retval = retval.ToUpper();
    }
    return retval;
}
     
    Example
    
        string g = "potatoe";
return g.ToUpperCheckForNull();
will return "POTATOE"