Net Core 2.0 pass data from IPageFilter Attribute to Razor Pages PageModel

Question

How can i pass data(object) from IPageFilter Attribute to Razor Page PageModel. Can i create a ViewData["example"] = object in this filter?

I can do it like this;

    public void OnPageHandlerSelected(PageHandlerSelectedContext context)
    {
         //i want like this
        //ViewData["Member"] = memberUser;

        context.HttpContext.Items.Add("Member", memberUser);
    }

But i must get everytime this object from Items.

Any way can i do this work with ViewData or TempData ?

Answer 1

Unfortunately not. ViewData and TempData are only relevant to a PageResult and the filter pipeline doesn't even know what the Result will be.

The annoying thing is that the PageContext , which is used to create the PageHandlerXXXXContext , does have a ViewData property but you can't access it from the IPageFilter .

Answer 2

You can access the selected PageModel through the context's HandlerInstance property, like this:

public void OnPageHandlerSelected(PageHandlerSelectedContext context) {
    var pageModel = context.HandlerInstance as PageModel ??
        throw new Exception("This page filter must run in a PageModel.");

    pageModel.ViewData["Member"] = memberUser;
    ...
}

Considering that a IPageFilter is for Razor Pages only, I cannot see how HandlerInstance could ever be anything except a PageModel, but if anyone knows otherwise please correct me.

Answer 3

If you not define page model class for page then "HandlerInstance as PageModel" is always be null. In this case need to check as Page:

public async Task OnPageHandlerExecutionAsync(PageHandlerExecutingContext context, PageHandlerExecutionDelegate next)
{
    PageContext pageContext = null;

    if (context.HandlerInstance is Page page) { pageContext = page.PageContext; }
    else if(context.HandlerInstance is PageModel pageModel) { pageContext = pageModel.PageContext; }

    if (pageContext != null)
    {
        pageContext.ViewData["UserEmail"] = "email";
    }

    await next.Invoke();
}