在for循环和作用域中创建数组时遇到问题

我必须为数组的成员赋值（我不知道这是否是正确的术语）。我将数组成员如下所示：（所有这些代码都在公共类BWClass中）

public static BackgroundWorker[] bwCA = new BackgroundWorker[25];
public static int NumbwCA;
private static bool HasRunOnce = false;
public static void BackgroundWorkerInitializer(bool doFirst, int numbwCA)
{
    // Okay we got here. So we can presume that array checking (number not exceeding the array) is already done
    if (!HasRunOnce)
    {
        NumbwCA = numbwCA; // for access 
    } // Now it is impossible to stop less backgroundworkers then started later on in the code
    if (doFirst)
    {
        for (int i = 0; i < NumbwCA; i++)
        {
            string strpara = (numbwCA.ToString()); // Could also directly write numbwCA.ToString() directly in the RunWorkerAsync() method
            bwCA = new BackgroundWorker[NumbwCA];
            bwCA[i] = new BackgroundWorker();
            bwCA[i].WorkerReportsProgress = true;
            bwCA[i].WorkerSupportsCancellation = true;
            bwCA[i].DoWork += new DoWorkEventHandler(bwa_DoWork);
            bwCA[i].ProgressChanged += new ProgressChangedEventHandler(bwa_ProgressChanged);
            bwCA[i].RunWorkerCompleted += new RunWorkerCompletedEventHandler(bwa_RunWorkerCompleted);
            bwCA[i].RunWorkerAsync(strpara);
        }
    }
    else // DoSecond
    {
        // stop the backgroundworkers
        for (int i = 0; i < NumbwCA; i++)
        {
            if (bwCA[i].IsBusy == true)
            {
                bwCA[i].CancelAsync();
                HasRunOnce = false; // If restarting the server is required. The user won't have to restart the progrem then
            }
            else
            {
                Console.WriteLine(">>The backgroundworkers are already finished and don't need canceling");
            }
        }
    }
}

所有这些代码都在一个公共类中。我想，当我在一个类中完成所有的数组制作时，我就不会再遇到变量作用域的问题了。但我错了。当bwCA[I].IsBusy=true运行时，我仍然会得到Error nullReferenceException。也可能是当for循环之外的任何东西运行时。

我知道如果声明了bwCA[I]，我就不能在循环外使用它，但我该如何更改它，以便我可以访问代码中的其他任何地方（如"else//DoSecond"中）？

顺便说一句。我不喜欢使用列表

// here for instance
bwCA = new BackgroundWorker[NumbwCA];
if (doFirst)
{
    for (int i = 0; i < NumbwCA; i++)
    {
        string strpara = (numbwCA.ToString()); 
       // bwCA = new BackgroundWorker[NumbwCA];