File editing without changing structure

 File editing without changing structure
       
 
 
 Hi,

   I am trying to open and edit a tab delimited file. I need to replace one column header with a token. I am able to open and edit the file, however, the file structure ends up changing.

For example, if I have a file "data.txt" with a column name "Email" on the first line and I want to replace this with a standard token "Your Email"

I can read the line and use a regular expression to replace the column name with the token. Now when I try to write the line back into the same file using the WriteLine method of a streamwriter it overwrites part of the second line of "data.txt"

Is there a way I can go into files and edit parts of it without chainging the file. I know it can be done in Java, but is it possible in C##

I dont want to create a new file, only edit the current file I have

Thanks

Umer

For reference this is what I am doing

 

try

{


sr = new StreamReader(filename);


//create a StreamReader to read file

String line;


line = sr.ReadLine();

//read first line of the file

if(sr!=null)

sr.Close();


sb = new FileStream(filename, FileMode.OpenOrCreate);

//create a new file stream with Open or Create access

sw = new StreamWriter(sb);

int k = token.Length;

 // If you just use the StreamWriter without wrapping it in FileStream you overwrite the file.

// It does not replace the first line. FileMode.OpenOrCreate lets you open the file and write to it.

if(token.Length<email.Length)

{

for(int i=0;i<email.Length - k ;i++)

{

token = token + " ";

}



string line1 = Regex.Replace(line, email, token, RegexOptions.Compiled|RegexOptions.Singleline|RegexOptions.IgnoreCase);

//replace occurence of email with desired token case insensitive

sw.WriteLine(line1);

//Write to the file

 

 

if(sw!=null)

sw.Close();

if(sb!=null)

sb.Close();



}




catch (Exception e)

{

System.Diagnostics.Debug.WriteLine(e.Message);

}

finally

{

if(sr!=null)

sr.Close();

if(sw!=null)

sw.Close();

if(sb!=null)

sb.Close();


}