How to replace a particular text line completely which starts with a specific word

See more:

C#

ASP

MVC3

console

ASP.NET5

I have a text file. My requirement is to replace the particular line completely with the input. My problem is only half of that line is constant and the remaining half can be anything.



So far I have tried the below

static void Main(string[] args)
        {
            //1.Copy the file from one location to another location
            string sourcePath = @"D:\\SQLConfigurationFile\\ConfigurationFile.ini";
            string destinationPath = @"C:\\Temporary\\ConfigurationFile.ini";
            File.Copy(sourcePath, destinationPath);
            //--End 1--//
                        
            string productKey = "Ali";
            string userName = "Mujtaba";

            string filePath = @"C:\\Temporary\\ConfigurationFile.ini";
            var text = new StringBuilder();
            var text2 = new StringBuilder();

            foreach (string s in File.ReadAllLines(filePath))
            {
                text.AppendLine(s.Replace("PID=ProductKey", "PID=" + "\"" + productKey + "\""));
            }

            using (var file = new StreamWriter(File.Create(filePath)))
            {
                file.Write(text.ToString());
            }

            foreach (string s in File.ReadAllLines(filePath))
            {
                text2.AppendLine(s.Replace("SQLSYSADMINACCOUNTS=User", "SQLSYSADMINACCOUNTS=" + "\"" + userName + "\""));
            }

            using (var file = new StreamWriter(File.Create(filePath)))
            {                
                file.Write(text2.ToString());
            }
            

        }

What I have tried:

For instance:
" PID=ProductKey"

Here PID is constant and ProductKey can be anything. For now I have hard coded ProductKey and tried the below code which is working.
But when the ProductKey changes my code won't work.

Please Help!!