C# Detecting null characters in a string array

Question

I am reading in from a text file using StreamReader into a string array text[]. One of the lines in the textfile is being read in as "\0" in positions 1 -> 20 of the array. How would I go about detecting this null character and ignoring this line.

Code example:

StreamReader sr = new StreamReader(Convert.ToString(openFileDialog1.FileName));
while (!sr.EndOfStream)
{
    string l= sr.ReadLine();
    string[] parsedLine = l.Split(new char[] { '=' },StringSplitOptions.RemoveEmptyEntries);
    // Not working:
    if (parsedLine.Length == 0)
    {
        MessageBox.Show("Ignoring line");
    }

Any help would be great!

Could you not just do `if(l.contains("/0"){l.replace("/0","");}` — dtsg, Jun 21 '12 at 10:09
What is `line` doing there you haven't defined it anywhere is it `l` ?? — yogi, Jun 21 '12 at 10:11
@Duane. This does not work as `'\0` is seen as a null character, not a series of character "\0" — Daniel Flannery, Jun 21 '12 at 10:43
@L337BEAN Yep, wasn't 100% sure so didn't post it as an answer — dtsg, Jun 21 '12 at 10:47

Me.Name · Accepted Answer · 2012-06-21T12:09:53.163

3

Assuming you mean a character with ascii code: 0

   if (parsedLine.Length == 0 || parsedLine[0] == '\0')continue;

edit the above will work if parsedLine is a string, but for the parsing in your code:

    string[] parsedLine = l.Split(new char[] { '=' },StringSplitOptions.RemoveEmptyEntries)
                      .Where(s=>s.Length != 1 || s[0] != '\0').ToArray();

edited Jun 21 '12 at 12:09

answered Jun 21 '12 at 10:11

Me.Name

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Does not work. Operator "==" cannot be applied to operands of type 'string' and 'char' – Daniel Flannery Jun 21 '12 at 10:16
@L337BEAN Oops, sorry, didn't read correctly, thought parsedLine was a read in string, added a linq alternative for the string array. – Me.Name Jun 21 '12 at 10:21
This is working to a certain extent. The problem now is that It is removing everything from the string each time. For example if `l` contains `H/0e/0l/0l/0o/0` after your line of code its passing l to parsedLine as `""`. I would like to keep the `hello` – Daniel Flannery Jun 21 '12 at 10:30
hmm, this may be due to a space in the logfile. Ill check on it. – Daniel Flannery Jun 21 '12 at 10:33
The logfile is riddles with null characters. The programs is picking up spaces as them and saving them null characters. Only way I can see to get around this is to check if the first character of l is null and the second character is `=` – Daniel Flannery Jun 21 '12 at 10:45
2

@L337BEAN So it's more a matter of removing all occurences of \0 than to remove entries where only a \0 is entered? In that case you could use l = l.Replace("\0", " ") to replace with spaces or l = l.Replace("\0", ""); to remove them altogether. Would that be viable? – Me.Name Jun 21 '12 at 11:14
Well I want to remove empty lines ( which I can do ), and lines thats first character is `\0` and second character `=`. These are being used as breaks in the logfile. eg: `= = = = = = = =` is being read as `=\0=\0=\0=\0=\0=\0=\0=\0` – Daniel Flannery Jun 21 '12 at 11:57
@L337BEAN For that example, the 2nd code sample should work, but I think the replace mentioned before still is easiest: string l= sr.ReadLine().Replace("\0",""); For the last example that would create a lot of empty elements after the split, but they would be removed with the RemoveEmtpyEntries clause. If the replace is not a viable solution, could you post (or upload) a longer sample file with the different scenarios? – Me.Name Jun 21 '12 at 12:14
The trouble is that `line.Replace("\0", "");` is not working. printing the string after running this still shows the `\0` as spaces. – Daniel Flannery Jun 21 '12 at 12:20
Wait. I believe im using it wrong. Update: yes, your correct. this is working. – Daniel Flannery Jun 21 '12 at 12:24

score 1 · Answer 2 · edited Jun 22 '12 at 08:59

1

Use the built-in String.IsNullOrEmpty() method:

if (!string.IsNullOrEmpty(l))
{
    // your code here
}

edited Jun 22 '12 at 08:59

Bobby

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answered Jun 21 '12 at 10:11

Estefany Velez

328
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18

The line to ignore can contain other characters. – bruno conde Jun 21 '12 at 10:14
@brunocondeq - What characters would those be? Based on the MSDN documentation it would ignore a null character and an empty string. – Security Hound Jun 21 '12 at 11:34

score 1 · Answer 3 · answered Jun 21 '12 at 10:22

1

Just ignore the line if it contains the null character.

string l = sr.ReadLine();
if (string.IsNullOrEmpty(l) || l[0] == '\0'))
   continue;
...

answered Jun 21 '12 at 10:22

bruno conde

47,767
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score 1 · Answer 4 · answered Jun 21 '12 at 10:31

Here is a linq solution that should work:

StreamReader sr = new StreamReader(Convert.ToString(openFileDialog1.FileName));
while (!sr.EndOfStream)
{
    string l= sr.ReadLine();
    bool nullPresent = l.ToCharArray().Any(x => x.CompareTo('\0') == 0);

    if (nullPresent)
    {
        MessageBox.Show("Ignoring line");
    }
    else
    {
        // do other stuff
    }
}

xdazz · Answer 5 · 2012-06-21T10:24:42.717

0

string l= sr.ReadLine();
if (l == "") {
  MessageBox.Show("Ignoring line");
  continue;
}

edited Jun 21 '12 at 10:24

answered Jun 21 '12 at 10:11

xdazz

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The line to ignore can contain other characters. – bruno conde Jun 21 '12 at 10:15
This is not working. `string does not contain a definition for 'isEmpty'` Am I missing an assembly reference or something ? – Daniel Flannery Jun 21 '12 at 10:19
He probably means `string.IsNullOrEmpty("string")` – dtsg Jun 21 '12 at 10:25
@L337BEAN I missed, in C#, `l == ""` is ok for testing empty string. – xdazz Jun 21 '12 at 10:26

C# Detecting null characters in a string array

5 Answers5