Why got empty lines?

Dave

Hi,
In Application.StartupPath + @"\Test.txt" got
11111
2222
3333
Read them and print out:
string ss = System.IO.File.ReadAllText(Application.StartupPath + @"\Test.txt");
string[] items = ss.Split('\n');
foreach(string item in items)
Console.WriteLine(item);
Why got empty lines as follows:
11111
(empty line here)
2222
(empty line here)
3333

7 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
Accepted answer
A good question, Dave!

The (unsatisfactory) answer is that all the overloads of the String.Split method which use a string as a separator require you to use a string array rather than just a (scalar) string:

http://msdn.microsoft.com/en-us/library/system.string.split(v=vs.110).aspx

A curious design decision by the .NET framework team :(

However, you can use Regex.Split instead:

string[] items = System.Text.RegularExpressions.Regex.Split(ss, "\r\n");
Vulpes12y ago
According to the docs, the Convert.ToDateTime method ignores leading, trailing and inner white-space when attempting to parse a string to a DateTime. So it doesn't matter if your string begins or ends with space, \r, \n or \t.

Although it doesn't appear to be documented, I think that Convert.ToInt32 (and to all other numeric types) also ignores leading and trailing (but not inner) white-space as well. However, to be on the safe side, you can always apply the Trim() method to the string before attempting to convert it.
Dave12y ago
Actually, I am testing my program: Get subString in each line of Test.txt (I don't want to get them line by line), then do something to subString, such as Convert.ToDateTime(subString) Is it ok that subString got space, \r, \n or \t at start or end?
Dave12y ago
Yes, it works! However, why not ss.Split("\r\n", StringSplitOptions.None);
Vulpes12y ago
Yep, that's the same as me.

Notice the 0D byte before each 0A.

In Windows, the line terminator is \r\n which in hex bytes is 0D 0A or 13 10 in decimal.

So when you split on '\n', the first two items in the array will end with '\r'. Now, normally, printing '\r' (known as carriage return) to the console causes the cursor to jump back to the beginning of the current line and when I run the code myself there are no empty lines.

It therefore appears that, for some unknown reason, '\r' is generating a new line on your console rather than a carriage return.

As an experiment, you could try this code to see if a blank line appears:

Console.WriteLine("One\r");
Console.WriteLine("Two\r");

though the following code should get rid of them altogether:

string ss = File.ReadAllText(Application.StartupPath + @"\Test.txt");
string[] items = ss.Split(new string[]{"\r\n"}, StringSplitOptions.None);
foreach(string item in items)
Console.WriteLine(item);
Dave12y ago
31 31 31 31 31 0D 0A 32 32 32 32 0D 0A 33 33 33 33 The thread 0x178 has exited with code 0 (0x0).
Vulpes12y ago
If you run this code, what's the output?

byte[] ba = System.IO.File.ReadAllBytes(Application.StartupPath + @"\Test.txt");
for(int i = 0; i < ba.Length; i++)
{
Console.Write("{0:X2} ", ba[i]);
if(ba[i] == 10) Console.WriteLine();
}