C#: Append text to text file between two lines

Question

I have in a txt file the following:

TOP:

BOTTOM:
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I want to add between those lines strings adding also a newline. How can I do this?

The end Result should be this after adding:

TOP:
<newaddedstring1>
<newaddedstring2>
<etc...>
BOTTOM:
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UPDATE: THE NEW CODE WHICH SEEMS TO WORK:

public class Program
{
    public static void Main()
    {
        string filename = @"/test.txt"; //File provided as dummy
        string location = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location) + filename; //Full Directory path will be in the same folder as the project
        List<string> data = File.ReadAllLines(location).ToList(); //Convert data to list

        List<string> rt = InjectAndPrint(data);
        File.WriteAllLines(location, rt);


    }

    static List<string> InjectAndPrint(List<string> textToSearch)
    {
        string windex = "Windows:";
        string lindex = "Linux:";
        string winiplist = "127.0.0.1,127.0.0.2,127.0.0.3,127.0.0.4,127.0.0.5,127.0.0.6,127.0.0.7,127.0.0.8,127.0.0.9,127.0.0.10,127.0.0.0";
        string liniplist = "192.168.74.133,192.168.74.118,192.168.74.155";
        List<string> winip = winiplist.Split(',').ToList<string>();
        List<string> linip = liniplist.Split(',').ToList<string>();
        List<string> arr = textToSearch;
        Parallel.ForEach(winip, text => {
            arr.Insert(arr.IndexOf(windex) + 1, text);
        });
        Parallel.ForEach(linip, text => {
            arr.Insert(arr.IndexOf(lindex) + 1, text);
        });
        return arr;
    }
}
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Answer 1

You don't need to use SkipWhile() or TakeWhile(). Just simply search the BOTTOM: and insert your line (Or search the TOP: index + 1 and insert:

static List<string> InjectAndReturn(
    string textToSearch,
    string searchTerm,
    string textToInject)
{
    var arr = textToSearch.Split('\n').ToList();
    arr.Insert(arr.IndexOf(searchTerm), textToInject);
    return arr;
}

var data = "TOP:\nBOTTOM:";

var rt = InjectAndReturn(data, "BOTTOM:", "<New Line>");


rt.ForEach(x =>
{
    Console.WriteLine(x);
});
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DotNet Fiddle