ThreadArrayExtensions is static class (module) containing extension-methods for System.Threading.Thread[] type.

ThreadArrayExtensions.cs

using System;
using System.Threading;

namespace Helpers
{
    public static class ThreadArrayExtensions
    {
        public static Thread[] StartAll(this Thread[] threads, params object[] values)
        {
            if (values.Length == 0)
            {
                for (int i = 0; i < threads.Length; i++)
                    threads[i].Start();
            }
            else if (values.Length == 1)
            {
                for (int i = 0; i < threads.Length; i++)
                    threads[i].Start(values[0]);
            }
            else
            {
                for (int i = 0; i < threads.Length; i++)
                    threads[i].Start(values[i]);
            }
            return threads;
        }

        public static Thread[] WaitAll(this Thread[] threads)
        {
            for (int i = 0; i < threads.Length; i++)
                threads[i].Join();
            return threads;
        }

        public static Thread[] WaitAll(this Thread[] threads, TimeSpan timeout)
        {
            for (int i = 0; i < threads.Length; i++)
                threads[i].Join(timeout);
            return threads;
        }
    }
}