App with MVC Virtual application shared AuthCookie

I have a 3.5 ASP.Net WebForm parent application. The parent uses forms authentication.

I have a MVC child virtual application, I would like to make it so the user logs in to the parent application, user then navigates to the virtual application by pressing a link on the parent. However every time I do this it goes to the login screen for the virtual application.

Is there a web setting I should double check in Parent? Or Child?

Is there an IIS setting that I should check?

Should I be using a virtual directory instead of virtual appli开发者_开发问答cation? I want the child to be able to access the Session[] from the parent. I would like the child app to use the same authCookie as the parent app.

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For single signon scenario's make sure in the web config:

Validation and decryption keys must exactly match and cannot be set to "AutoGenerate". The validation and decryption algorithms must also be the same

You may need to set EnableCrossAppRedirects="true", depending on how you have configured your app.