为什么静态变量不能在ASP.NET中按预期方式工作？

Question

I built an ASP.NET application and a public static variable in it:

public static WebEndPointFlow[] EndPoints = new WebEndPointFlow[10];

where WebEndPointFlow is a my custom class.
The problem is: when I set some element of the array of EndPoints , it only can last for a very short time period. After minutes, the element becomes null .
I don't know what happens to my elements in the array. So I create a deathless thread to access these elements regularly, hoping GC won't process them. How pathetic, it does not work.
Any idea on how to remain my original elements always? Very appreciate!

======================================
So the problem does not matter with GC? I agree.
But why my elements become null?

===========================
One more question: does this array look the same when different users access it?
code of Class:

public class WebEndPointFlow
    {
    private static readonly ILog logger = LogManager.GetLogger(typeof(WebEndPointFlow));

    private InstantMessagingFlow flow;

    public InstantMessagingFlow Flow
    {
        get { return flow; }
    }
    private UserEndpointSettings userEndpointSettings;
    private UserEndpoint endPoint;

    public UserEndpoint EndPoint
    {
        get { return endPoint; }
        set { endPoint = value; }
    }

    public StringBuilder Transcript { get; set; }

    private WebSocketServer wsServer;
    private Conversation conversation;

    // position in the array of 'endPoints'
    private int position;
    public int Position
    {
        get { return position; }
        set { position = value; }
    }
    private FailureResponseException e = null;
    private string _TargetLyncUser;
    public string TargetLyncUser
    {
        get { return _TargetLyncUser; }
        set { _TargetLyncUser = value; }
    }
    private bool sendTrans = false;
    public int Duration
    {
        get;
        set;
    }

    public WebEndPointFlow()
    {
    }

Answer 1

Rather than a garbage collector issue ( as comments in your question have pointed out, and you should find Eric Lippert a good source anyway! ), it might be something with Internet Information Services application pool's recycling.

Default application pool settings will force a recycle after some idle time. Also, an application pool can go down if there's a fatal error (like a stack overflow) which can kill the IIS worker process. Other situation might be an extreme memory leak.

In summary:

• Go to your application's application pool settings and try to increase the idle time: ( NOTE: You shouldn't set this setting permantly: I'm suggesting this for debugging purposes in order to let you discover how application pool model works ).
• Add an Application_Error handler in your Global.asax and log exceptions there and see if something is going wrong after some time.