IndexOutOfRangeException being thrown from a call to Dictionary.Add?

[Adam Clauss]

This does not seem to be a documented exception.
See: http://msdn2.microsoft.com/en-us/library/k7z0zy8k.aspx


System.IndexOutOfRangeException: Index was outside the bounds of the array.
at System.Collections.Generic.Dictionary`2.Resize()
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value,
Boolean add)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
<our code removed from callstack>

Any ideas on what would cause this?

 

[Marc Gravell]

The only thing I can think of is if your key instance is itself throwing
this exception in the GetHashCode() or Equals() methods; do you have any
(cut-down) sample code to illustrate this?

Marc

 

[Adam Clauss]

The only thing I can think of is if your key instance is itself throwing
this exception in the GetHashCode() or Equals() methods; do you have any
(cut-down) sample code to illustrate this?

The Dictionary in question is: Dictionary<string, int> so if
string.GetHashCode were to be throwing this exception, I don't know what I
could do about it anyway...

Unfortunately I'm not sure if I can trim this down any. This is part of a
rather complex system - and we cannot actually duplicate this here in our
development environment. It is being seen at the client's site.

I even poked around using Reflector into that last call to
Dicitonary.Resize, but could not find any reason for
IndexOutOfRangeException to be thrown.

 

[Marc Gravell]

OK, probably rule that one out then! (assuming you aren't passing in your
own comparer).

Next try: is there any threading going on? Perhaps one thread is removing
things as another thread is causing resize... I can't see any specific lock
in reflector, so I assume that these methods are *not* thread-safe without
your own sync.

Marc

 

[Marc Gravell]

aside: if this is a aspnet project and the dictionary is static, then the
same applies even without your own threads

Apols if this seems obvious; it comes as quite a shock to some people...

Marc

 

[Adam Clauss]

aside: if this is a aspnet project and the dictionary is static, then the
same applies even without your own threads

Apols if this seems obvious; it comes as quite a shock to some people...

Marc

Haha, I welcome anything, obvious or otherwise. And no - not ASP.NET. It's
a Windows Service.

Still the threading is a possibility I am looking into. We are doing some
synchronization, but I am wondering if we have a case which is slipping
through.