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Editorial Team
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Asked: 2026-05-28T18:16:16+00:00

This week, several of our .NET (C#) web applications have been thowing the error

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This week, several of our .NET (C#) web applications have been thowing the error “Operation is not valid due to the current state of the object“.

They are all web apps and share the same front-end and database servers although they all query separate databases.

I’ve never seen this error before, so when it appeared in three seemingly unrelated apps I thought something must be up.

My question is not so much as to what the error means, but whether anyone knows of a possible change to the server which could introduce a condition where this is more likely to happen?

I know the front-end server was restarted recently so a config setting could have been changed there but the database server has been up all the time.

Looking at a stack trace, one app mentions ThrowIfMaxHttpCollectionKeysExceeded() but there has been no increase or indeed any change to any of the apps’ code-behind which could trigger such an error.

What could have changed?

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1 Answer

  1. Editorial Team

    Have you applied any security updates lately?

    Microsoft recently patched several security holes: Microsoft Security Bulletin MS11-100.

    One potential side-effect of the fix is that HTTP submissions with lots of elements — for example, forms with lots of fields — will cause an InvalidOperationException to be thrown from ThrowIfMaxHttpCollectionKeysExceeded.

    If your application legitimately needs to submit many elements then you can edit your web.config to raise the limit:

    <appSettings>
    <add key="aspnet:MaxHttpCollectionKeys" value="2000" />
</appSettings>
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