Bug 60654 - NavigationPage via x:Arguments XAML: runtime error
Summary: NavigationPage via x:Arguments XAML: runtime error
Alias: None
Product: Forms
Classification: Xamarin
Component: Forms ()
Version: 2.5.0
Hardware: PC Windows
: Normal major
Target Milestone: ---
Assignee: Bugzilla
Depends on:
Reported: 2017-11-13 20:30 UTC by Adam Patridge [MSFT]
Modified: 2017-11-14 00:20 UTC (History)
3 users (show)

Tags: navigationpage, x:Arguments, xaml, ac
Is this bug a regression?: ---
Last known good build:

Reproduction solution (following listed steps) (1.50 MB, application/x-zip-compressed)
2017-11-13 20:30 UTC, Adam Patridge [MSFT]

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Description Adam Patridge [MSFT] 2017-11-13 20:30:59 UTC
Created attachment 25676 [details]
Reproduction solution (following listed steps)

While it may not be the ideal way to construct a NavigationPage, trying to create it entirely in XAML with x:Arguments parameters for the root page will throw an exception at runtime (confirmed on iOS, Android, and UWP).

## Steps

1. File > New Forms cross-platform app
2. Change generated MainPage.xaml.cs class to a NavigationPage
3. Change MainPage.xaml XAML to something like this

<NavigationPage xmlns="http://xamarin.com/schemas/2014/forms"
                    <Button Text="Click me" />

4. Run app on iOS, Android, or UWP

This also applies when a page is a separate XAML file and is included as the value(s) in the `x:Arguments` content.

## Expected

App would load with a navigation page starting with the single-button root page.

## Actual

Exception thrown.

> [on iOS] System.InvalidOperationException: NavigationPage must have a root Page before being used. Either call PushAsync with a valid Page, or pass a Page to the constructor before usage.

## System info

Microsoft Visual Studio Enterprise 2017 
Version 15.4.3
Microsoft .NET Framework
Version 4.7.02556

Installed Version: Enterprise

Architecture Diagrams and Analysis Tools   00369-60000-00001-AA352
Microsoft Architecture Diagrams and Analysis Tools

Visual Basic 2017   00369-60000-00001-AA352
Microsoft Visual Basic 2017

Visual C# 2017   00369-60000-00001-AA352
Microsoft Visual C# 2017

Visual F# 4.1   00369-60000-00001-AA352
Microsoft Visual F# 4.1


Xamarin (34c1b6c)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin.Android SDK (HEAD/c2a33d8ea)
Xamarin.Android Reference Assemblies and MSBuild support.

Xamarin.iOS and Xamarin.Mac SDK (51128b8)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.