C# Detecting null characters in a string array

c# arrays streamreader

11,747

Solution 1

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();

Solution 2

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

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

Solution 3

Just ignore the line if it contains the null character.

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

Solution 4

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
    }
}

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11,747

Author by

Daniel Flannery

Software Engineer. Polyglot programmer.

Updated on August 06, 2022

Comments

Daniel Flannery almost 2 years
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!
- dtsg almost 12 years
  
  Could you not just do if(l.contains("/0"){l.replace("/0","");}
- yogi almost 12 years
  
  What is line doing there you haven't defined it anywhere is it l ??
- Daniel Flannery almost 12 years
  
  sorry. line should have been l. typo.
- Daniel Flannery almost 12 years
  
  @Duane. This does not work as '\0 is seen as a null character, not a series of character "\0"
- dtsg almost 12 years
  
  @L337BEAN Yep, wasn't 100% sure so didn't post it as an answer
bruno conde almost 12 years

The line to ignore can contain other characters.
bruno conde almost 12 years

The line to ignore can contain other characters.
Daniel Flannery almost 12 years

Does not work. Operator "==" cannot be applied to operands of type 'string' and 'char'
Daniel Flannery almost 12 years

This is not working. string does not contain a definition for 'isEmpty' Am I missing an assembly reference or something ?
Me.Name almost 12 years

@L337BEAN Oops, sorry, didn't read correctly, thought parsedLine was a read in string, added a linq alternative for the string array.
dtsg almost 12 years

He probably means string.IsNullOrEmpty("string")
xdazz almost 12 years

@L337BEAN I missed, in C#, l == "" is ok for testing empty string.
Daniel Flannery almost 12 years

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 almost 12 years

hmm, this may be due to a space in the logfile. Ill check on it.
Daniel Flannery almost 12 years

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 =
Me.Name almost 12 years

@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?
Security Hound almost 12 years

@brunocondeq - What characters would those be? Based on the MSDN documentation it would ignore a null character and an empty string.
Daniel Flannery almost 12 years

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
Me.Name almost 12 years

@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?
Daniel Flannery almost 12 years

The trouble is that line.Replace("\0", ""); is not working. printing the string after running this still shows the \0 as spaces.
Daniel Flannery almost 12 years

Wait. I believe im using it wrong. Update: yes, your correct. this is working.