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2025-07-02 19-21-41
Carla Ribeiro da Fonseca
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2Comments
"The URL-encoded form data is not valid" error message
Question
If you get this error it's because...

You (or some else) installed update MS11-100 (https://technet.microsoft.com/en-us/security/bulletin/ms11-100)
and
You have too many fields in your form. Way too many. More than 1000, actually.

The only real solution is to change your form so you don't have that many fields.

The temporary fix -- until you publish the eSpace -- is to add the line
<add key="aspnet:MaxHttpCollectionKeys" value="some number here"/>
in the <appSettings> in web.config.

For more info, Scott Guthrie to the rescue: https://weblogs.asp.net/scottgu/archive/2011/12/28/asp-net-security-update-shipping-thursday-dec-29th.aspx

Hope this helps!
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03 Feb 2012
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2018-11-07 10-57-20
Carolina Bessa
Hi!!
I started to get this error now, and my form has 5 fields
:(
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17 Sep 2012
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2019-11-12 17-31-26
Justin James
 
MVP
I got that error too, and I doubt that I had anywhere near 1,000 fields in my form as well, but following the fix that Carlos recommends did fix the issue for me a few months ago.

J.Ja
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18 Sep 2012
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