C# Replace specific line number

How can I use this method to receive an integer index number and then replaces the string in that particular line:

public void replace (int index)
        {

             try
            {
                String strFile = File.ReadAllText("c:\\test.txt");

           
                if (strFile.Contains("A"))
                        {
                            strFile = strFile.Replace("P", "A");
                            strFile = strFile.Replace(" ", ";");

                            File.WriteAllLines("c:\\test.txt", strFile[index]);
                        
                        }
     
                        
                        

            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

        }

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pauledwardianAsked:
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Mike TomlinsonHigh School Computer Science, Computer Applications, and Mathematics TeachersCommented:
Something like:
        public void replace(int index) // <-- zero based index: line #1 is at index 0 (zero)
        {
            try
            {
                String[] lines = File.ReadAllLines("c:\\test.txt");
                if (lines.Length > index)
                {
                    lines[index] = lines[index].Replace("P", "A").Replace(" ", ";");
                    File.WriteAllLines("c:\\test.txt", lines);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

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Mike TomlinsonHigh School Computer Science, Computer Applications, and Mathematics TeachersCommented:
*Oops...I forgot to add your check for "A" back in:
        public void replace(int index) // <-- zero based index: line #1 is at index 0 (zero)
        {
            try
            {
                String[] lines = File.ReadAllLines("c:\\test.txt");
                if (lines.Length > index)
                {
                    if (lines[index].Contains("A"))
                    {  
                        lines[index] = lines[index].Replace("P", "A").Replace(" ", ";");
                        File.WriteAllLines("c:\\test.txt", lines);
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

Open in new window

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pauledwardianAuthor Commented:
Fantastic!
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C#

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