"Object reference not set to an instance of an object"

[Bob Cannistraci]

A three-tier user authentication system was running without a problem for almost a year and now is suddenly dysfunctional. We don't know of any changes to any of the servers. It's quite maddening. The details:

1) We know the COM+ app is instanced on the COM+ server (Win 2000). The component graphic spins when CreateObject is called.

2) The proxy is installed on an IIS server (Win 2000) with delivers the interface, written in ASP, to the client PC.

3) These are the error messages displayed when a method of DAMS is called:

----------------------------------------------------

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 116:
Line 117im MyContextClass as Object = Server.CreateObject("DAMS.Context")
Line 118im MyContextArray as System.Array = MyContextClass.list <<< THIS LINE FAILS
Line 119im MyCounter as Integer
Line 120im MySiteID, MySiteName as String

Source File: C:\IntranetLoginService\login.aspx Line: 118

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
Microsoft.VisualBasic.CompilerServices.LateBinding.LateGet(Object o, Type objType, String name, Object[] args, String[] paramnames, Boolean[] CopyBack) +899
ASP.Login_aspx.__Render__control1(HtmlTextWriter __output, Control parameterContainer) in C:\IntranetLoginService\login.aspx:118
System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +27
System.Web.UI.Control.Render(HtmlTextWriter writer) +7
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +243
System.Web.UI.Page.ProcessRequestMain() +1929

-----------------------------------------------------

4) Moving the COM+ app and ASP script to other servers does not solve the probelm.

5) When the app is directly called from a Win32 client there is no problem.

6) Finally, all servers are patched and up to date.

The NullReferenceException is baffling and the stack trace is not helpful in determining what the problem can be.

Any advice you can give will be appreciated. We need this problem debugged ASAP. Please let me know if you need more information.

Bob

 

[Bob Barrows [MVP]]

Bob Cannistraci wrote:
<snip>
Posting the same message over and over will not improve your chances of
getting an answer. Why don't you answer Patrice's question? Here it is
again:

Is MyContextClass Nothing ?

It looks like that Server.CreateObject returns Nothing. COM+
configuration such as an expired, locked account ?

Patrice

A quick glance at your code reveals some .Net-looking code. You may wish to
post this to one of the dotnet newsgroups.

Bob Barrows