How do I disable request validation without setting RequestValidationMode to 2.0?

We've just upgraded to ASP.NET 4.0, and found that requestValidation no longer works. The MSDN docs suggest we need to set requestValidationMode in web.config to 2.0:

4.0 (the default). The HttpRequest object internally sets a flag that indicates that request validation should be triggered whenever any HTTP request data is accessed. This guarantees that the request validation is triggered before data such as cookies and URLs are accessed during the request. The request validation settings of the pages element (if any) in the configuration file or of the @ Page directive in an individual page are ignored.

2.0. Request validation is enabled only for pages, not for all HTTP requests. In addition, the request validation settings of the pages element (if any) in the configuration file or of the @ Page directive in an individual page are used to determine which page requests to validate.

This will work for us, however I'm a little puzzled. It seems that we're putting this into a legacy/compatibility mode. Surely it should be possible to have the 4.0 behaviour, but still have an option to turn this off on a page?

I found a way to achieve this without changing RequestValidationMode to 2.0 to the whole site:

You can crate a sub-directory for the page you want to disable the request validation and add a new web.config to this directory with RequestValidationMode set to 2.0, this way only this directory will work in 2.0 mode without affecting all other requests that will work in 4.0 mode.

I think you can add an location section to your main web.config specifying only one page, but I didn't tested this yet. Something like this:

<location path="Admin/Translation.aspx">
    <system.web>
        <httpRuntime requestValidationMode="2.0"/>
    </system.web>
</location>

Hope it helps you as helped me !

Your best bet is to override the requestValidationType with your own code:

<httpRuntime requestValidationType="YourNamespace.YourValidator" />

MSDN link

It appears that it is not possible to turn this on or off for a page in requestValidationMode 4.0.

This whitepaper outlines breaking changes in .Net 4.0, of which this seems to be one. Even the whitepaper suggests reverting back to requestValidationMode 2.0

To revert to the behavior of the ASP.NET 2.0 request validation feature, add the following setting in the Web.config file:

<httpRuntime requestValidationMode="2.0" />

Although it also helpfully recommends

that you analyze any request validation errors to determine whether existing handlers, modules, or other custom code accesses potentially unsafe HTTP inputs that could be XSS attack vectors.

without giving any guidance on how best to resolve these issues

Rajeev Shenoy

You can set ValidateRequest to false in the page directive: