Why are Redirect Results not allowed in Child Actions in Asp.net MVC 2

I have some partial actions that I render with the Asp.Net Futures RenderAction method. Some of these perform redirects after the forms in them have been processed.

Now that I upgraded to Asp.Net MVC 2 RC it gives me an error "Child actions are not allowed to perform redirect actions".

I checked out the source code and I found the l开发者_StackOverflow社区ine that throws the exception. To Get around it I can make a custom RedirectResult, But before I do I want to understand why the framework doesn't allow it in the first place. There must be a good reason and maybe I Shouldn't do either.

Any one know the reason for this limitation?

Thanks

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The limitation exists because MVC has already started rendering a view to the client. The effect of redirecting from this point is undefined. It could work perfectly, it could continue rendering the original view without redirecting, it could throw a different exception, etc.

Since the result of performing this action is undefined, the framework blocks it. In practice, RenderAction should never be used to render anything other than a view (or view-like content) for similar reasons.

In your particular case, the outer action should redirect. If you're just going to end up redirecting from within the view anyway without showing anything to the user, then there was really no purpose to going through the view in the first place, as the outer action could have delegated the work appropriately on its own.

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Try to use something like this in Child Action:

ControllerContext.HttpContext.Response.Redirect(ControllerContext.HttpContext.Request.Url.ToString());

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My solution.

Action method:

return View("Redirect", model);

View:

<script type="text/javascript" language="javascript">
    document.location = '<%: Url.Action("Index", "Album", new { id = Model.Id }) %>';</script>

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In my case, the form being rendered is a "configure" panel on an extension to a website I'm building. I'd like the extension's own controller to be able to handle the form processing and then redirect back to the admin page listing all configured extensions. I don't think it's appropriate or practical here to ask the parent page's controller to process the form for the extension. What would you suggest I do instead?

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In my unusual case, I had a custom AuthorizeAttribute attached to my controllers which was attempting to redirect on a child action, which is (as mentioned above) not allowed.

To resolve the issue, I removed authorisation checking redirection on all child actions:

Public Overrides Sub OnAuthorization(filterContext As AuthorizationContext)
    //Child actions cannot redirect anyway, so no need to check permissions.
    If filterContext.IsChildAction Then Exit Sub

    .. parent authorisation checks ..

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Sometimes this error occured when you try to render an action of base action result. Example:

ActionResult X
    Return View
View X
    RenderAction Y

ActionResult Y
    // Bla bla
       return View 
    // else
       return RedirectToAction X

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In that case just point the partial view form's submit url to action that was the target of your problematic redirection and let it perform itself redirection to its GET version.