C# loop through app.config but only use keys like "service"
<p>I'm looping through a txt file currently to get server names and check a specific services status and start it if stopped. This works perfectly with my service names stored in my app.config.
What I want to do is also store my file path, file name, timeout, and any other keys I want to put in the app.config down the road. 
My issue is when I loop through the app.config currently I only have service names which works perfectly. If I add the other keys that I want to add I obviously will get "Service Not Found". 
How do I only pick keys that are "like" "service". I'm naming the keys "service1", 2, 3, etc. </p>

<pre><code>foreach (string key in ConfigurationManager.AppSettings)
{
    string value = ConfigurationManager.AppSettings[key];

    // Create an instance of StreamReader to read from a file.
    // The using statement also closes the StreamReader.
    using (StreamReader sr = new StreamReader(txtFilePath + txtFile))
    {
        String line;
        // Read and display lines from the file until the end
        // of the file is reached.
        while ((line = sr.ReadLine()) != null)
        {
            Console.WriteLine(line);

            // Check for lines with semi-colon. If semi-colon at
            // line start skip it
            if (line.StartsWith(";"))
            {
                continue;
            }
            else
            {
                ServiceController sc = new ServiceController(value, line);

                //Create new timeout module.
                TimeSpan timeout = new TimeSpan();

                //Write current service status to console.
                Console.WriteLine(
                    "The " + value + " service status is currently set to {0}",
                    sc.Status.ToString()
                );
</code></pre>
