How can i verify that all the threads are aborted ?

Hello friends,
Kindly fo through the following code sample,

In this code, i want to stop execution till all the threads have complited their job. and i dont know how can i do this.

static ArrayList FarchedContent = new ArrayList();
public static string SearchContent(string KeyWord)
{
objThread = new Thread[20];
for (int i = 0; i < 20; i++)
{
objThread[ i ] = new Thread(new ThreadStart(FatchContent));
objThread[ i ].Priority = ThreadPriority.AboveNormal;
objThread[ i ].Start();

}
//Here I want to use FarchedContent but i want to make sure that all the //above created threads have complited their job.
// How can I do this
}

private static void FatchContent()
{
string str;
//some task;
// Assign content to str
FarchedContent.Add(str);
Thread.CurrentThread.Abort();
}


can any one know how can i do this

Rgds,
Kiran Suthar