I’d like to read a Txt file with parameters and values then update the values of specific parameters. I don’t know the original value of the parameter before changing but have a list of parameter values that need changed. Writing the entire file with changed values to a new file is my goal.

I’m currently able to find the parameters, replace the lines with updated string, and write to a new file.

Structure of text file:
Parameter1=1.5
Parameter2=2.0
Parameter3=0.5

Output of new file when replacing Parameter1 and Parameter3:
Parameter1=0.7
Parameter3=3.0

Ideal output:
Parameter1=0.7
Parameter2=2.0
Parameter3=3.0

private string ProcessParameterUpdates(string selectedDPVFile, string parameterName, string parameterNameAndValue)
{
    List<string> dpvLines = new List<string>();
    string dpvLine;
    using (StreamReader reader = new StreamReader(selectedDPVFile))
    {
        string fileSelectedDirectory = Path.GetDirectoryName(selectedDPVFile);
        string outputFileName = Path.Combine(fileSelectedDirectory, "UpdatedParameters.dpv");

        while ((dpvLine = reader.ReadLine()) != null)
        {

            if (dpvLine.Contains(parameterName))
            {
                dpvLines.Add(dpvLine);
                dpvLine = dpvLine.Replace(dpvLine, parameterNameAndValue);
                if (File.ReadLines(outputFileName).Contains(parameterNameAndValue))
                {
                    writeWindow.SelectionColor = Color.DarkOrange;
                    writeWindow.AppendText("Parameter already updated: " + parameterNameAndValue + "n");
                    Debug.WriteLine("Parameter already updated: " + parameterNameAndValue + "n");
                    dpvLine = reader.ReadLine();
                    writeWindow.ForeColor = Color.Black;
                }
                else
                {
                    File.AppendAllText(outputFileName, dpvLine + "n");
                    writeWindow.AppendText(dpvLine + "n");
                    Debug.WriteLine(dpvLine + "n");
                }
            }
        }
        reader.Close();
    }
    return selectedDPVFile;
}