C#

"Caution:

The CompareTo method was designed primarily for use in sorting or alphabetizing operations. It should not be used when the primary purpose of the method call is to determine whether two strings are equivalent. To determine whether two strings are equivalent, call the Equals method."

while(!allDone)
    lock the streamreader (or some other object)
    read one line from the streamreader, and set allDone true if no more data available
    unlock again
    process the line read, if any
}

StreamReader sr;
bool allDone;

void handleFileWithManyThreads(string filename, bool waitTillDone) {
    allDone=false;
    sr=File.Open(filename);
    List<Thread> threads=new List<Thread>();
    // launch N threads
    for(int i=0; i<Environment.NumberOfProcessors; i++) {
        Thread thread=new Thread();
        thread.Start(runner);
        threads.Add(thread);
    }
    if (waitTillDone) {
        // now wait for all these threads to finish
        foreach(Thread thread in threads) thread.Join();
        sr.Close();
    }
}

void runner() {
    while(!allDone) {
        string line=null;
        lock(sr) {
            line=sr.ReadLine();
            if (line==null) allDone=true;
        }
        if (line!=null) {
            // process line here
        }
    }
}

ElementHost host = new ElementHost();
host.Dock = DockStyle.Fill;
host.Child = myWpfControl;