Resolving ASP.NET Error – ThrowIfMaxHttpCollectionKeysExceeded

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Issue

On December 29, 2011, Microsoft released a security update KB2656356 / MS11-100 for ASP.NET to address a potential Denial of Service vulnerability. In the update, Microsoft introduced a limit to the number of data elements on an ASP.NET form or on a JSON payload. The default limit is 1000 data elements.   Exceeding this limit will cause a ThrowIfMaxHttpCollectionKeysExceeded error.

In XMPro, this issue will occur during a post back event, e.g. submitting a form when there are more than 1000 controls on a form. This number is very easy to be exceeded, especially in data capturing type forms.

Resolution

Fortunately to fix this issue is very easy. To change the default MaxHttpCollectionKeys limit, add the following to your web.config file in the <appSettings> section in the <configuration> section and put a large value.

<appSettings>
<add key=”aspnet: MaxHttpCollectionKeys” value=”5000″></add>
</appSettings>

References

Knowledge Base article: http://support.microsoft.com/kb/2661403

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