c＃空字符串[]错误

Question

Someone please help me with this code its showing array outofbond exception .

datain file new_hosts.txt is like:

test      test       28/6/2015    09:45 PM
test      fafagf     30/6/2015    01:00 PM
test      sfaasfag   28/6/2015    10:05 PM

code:

public void notification()
    {
        string regvalue;
        int ctr = 0;
        bool isNotificationExits=false;
        string[] meetingdata=new string[]{};
        string[] notificationsdata = new string[]{};
        try
        {
            //ctr = File.ReadAllLines("new_hosts.txt").Length;
            meetingdata = File.ReadAllLines("new_hosts.txt");
        }
        catch (FileNotFoundException)
        {
            //showmainmenu();
        }
        List<String> notificationsdata = new List<String>();
        foreach(string data in meetingdata)
        {
            string trimed = data;
            //Console.WriteLine(data);
            Regex d = new Regex(@"(\d+[\/]\d+[\/]\d+)");
            Regex t = new Regex(@"(\d+)([\:])(\d+)\s(PM|AM)");
            Match mt =t.Match(trimed);
            Match md = d.Match(trimed);
            regvalue = md.Value +" " +mt.Value;
            DateTime datetime = new DateTime();
            if (md.Success && mt.Success)
            {
                datetime = DateTime.ParseExact(regvalue, "d/M/yyyy hh:mm tt", new CultureInfo("en-US"), DateTimeStyles.None);
                //Console.Write(datetime);
            }
            else { Console.WriteLine("Opps someting Went Wrong Please Contact Developer...!!!"); }//this is not going to happend ever
            if (!(datetime < DateTime.Now))
            {                   
                if (datetime <= DateTime.Now.AddDays(5))
                {
                    //Console.WriteLine(ctr + "   you here");
                    isNotificationExits = true;
                    notificationsdata[ctr]=data; <<-----Array Out Of bond Exception here
                    ctr++;
                }
            }                
        }

        if(isNotificationExits==true)
        {
            Console.WriteLine("\n\t\tHey..! You have Some Reminders here\n ");
            Console.Write("Sr.no |");
            Console.Write("    Subject    |");
            Console.Write("    Place    |");
            Console.Write("     Date     |");
            Console.WriteLine("    Time");
            for(int j=0; j <= notificationsdata.Length ; j++)
            {
                Console.WriteLine(j + 1);
                Console.WriteLine(notificationsdata[j]);
            }
            Console.WriteLine();
        }

    }

Answer 1

In addition to Nikola's point which you'll also need to fix is that you haven't set a size for the array

string[] notificationsdata = new string[]{};

If you don't know what the size is ahead of time, you can use another data structure such as a List<string> . I see you've created a List<string> object but you've named it the same as the array. This is confusing so you should either rename one of them or delete one.

To use the list, replace

notificationsdata[ctr]=data;

with

notificationsdata.Add(data);

Answer 2

You are not specifying where exactly you get the exception, but I would take the (not-so) wild guess and tell you that this piece of code is what bugs you:

for(int j=0; j <= notificationsdata.Length ; j++)
{
    Console.WriteLine(j + 1);
    Console.WriteLine(notificationsdata[j]);
}

Problem is, you are iterating over the array starting from index zero until index notificationsdata.Length . However, the Length method returns the number of items in the array, therefore an index with the array's length wouldn't exist.

What you can do to prevent this is simply change the less-than-or-equal sign to just less-than:

for(int j=0; j < notificationsdata.Length; j++)

or subtract one from the loop maximum:

for(int j=0; j <= notificationsdata.Length - 1; j++)

Answer 3

如果使用列表，则必须使用notificationsdata.Add(data)将项目添加到列表中。