Blazor UriHelper.NavigateTo is calling the page twice

Question

I created a new Blazor Server Side Application in Preview 8. When I call the UriHelper.NavigateTo to go to the counter page from the Index.razor page, the counter page is c

Answer 1

This behavior is because the pre-render feature. Notice that, when you are on counter page (loaded for twice), if you click on Home, only one execution is fired:

Summarizing:

When pre-render is enabled (by default), the prerended page's OnInitializedAsync is called for twice by design. For this reason, your redirect statement is executed for twice.

To test is I wrote this code on index OnInitializedAsync:

@page "/"
@inject IUriHelper UriHelper

Hello, world!

Welcome to your new app.

@code{

    protected async override Task OnInitializedAsync()
    {
        System.Console.WriteLine("_*   ");
        System.Console.WriteLine("_**************************");
        System.Console.WriteLine("_***** Pre render ******");
        System.Console.WriteLine("_**************************");
        System.Console.WriteLine("_   ");
        return;
    }
}

And I call the page using pre-render and from the app (without prerender). Noticed that when I force reload (prerended) the OnInitializedAsync is executed for twice:

Learn more about render modes.