I have a text file which is contain information about game level ; award that you get, already played or not, the level is locked or not?

i have format like this..

1,0,0,0 <<< first digit determine level , second is locked level , third is already played and the last one is award you get

when we pass each level , there is a script that modify the text file

i know how to read but don't know how to write in the location in the file that i want

for example i want to modify text file at level 5 so in text file "5,0,0,1" must be modify as 5,0,1,3 (because you already played), but most tutorial that i found it creates new text file or write new line but do not mofidy existing data.

how do i suppose to do?

public void readDataFromFileByLevel(int level)
{   
    StringBuilder sb = new StringBuilder();


    using (StringReader sr = new StringReader(levelAwardFile.text)) 
    {   
         string line;
        while ((line = sr.ReadLine()) != null)
        {           
         words = line.Split(',');
         if ( words.Length != 4 )
         {
          continue;
         }         
         int levelInFile = int.Parse(words[0]);   
         if ( levelInFile == level ) 
         {                               
             using (StringWriter sw = new StringWriter(levelAwardFile.text)) 
                {

          }

         }    
         else 
         {
          continue;
         }       
       }        
    }  
}