Xamarin.Forms Xaml OnPlatform not supporting in UWP

[jitendrajadav]

Description

Xamarin.Forms Xaml OnPlatform not supporting in UWP

while running application getting error like this please find below :

Xamarin.Forms.Xaml.XamlParseException: 'Position 26:102. Property UWP is not found or does not have an accessible getter'

Steps to Reproduce

1.Create any project with xamarin.form with UWP

1. create any style in App.xaml with

            <OnPlatform x:Key="ButtonLargeFontSize" x:TypeArguments="x:Double" iOS="40" Android="40" UWP="40"/>
<Style x:Key="ButtonLargeStyle" TargetType="Button">
                <Setter Property="VerticalOptions" Value="Center"/>
                <Setter Property="HorizontalOptions" Value="Start"/>
                <Setter Property="TextColor" Value="{StaticResource selectTextColor}"/>
                <Setter Property="FontSize" Value="{StaticResource ButtonLargeFontSize}"/>
                <Setter Property="Margin" Value="10,0,0,0"/>
                <Setter Property="BackgroundColor" Value="Transparent"/>
            </Style>

1. use into any content page

Expected Behavior

it should work as androind and iOS

Actual Behavior

getting error like

Basic Information

Microsoft Visual Studio Professional 2017
Version 15.8.8
VisualStudio.15.Release/15.8.8+28010.2048
Microsoft .NET Framework
Version 4.7.03190

Installed Version: Professional

Microsoft Visual Studio Tools for Applications 2017 00369-60000-00001-AA420
Microsoft Visual Studio Tools for Applications 2017

Visual C++ 2017 00369-60000-00001-AA420
Microsoft Visual C++ 2017

Application Insights Tools for Visual Studio Package 8.13.10627.1
Application Insights Tools for Visual Studio

ASP.NET and Web Tools 2017 15.8.05085.0
ASP.NET and Web Tools 2017

ASP.NET Core Razor Language Services 15.8.31590
Provides languages services for ASP.NET Core Razor.

ASP.NET Web Frameworks and Tools 2017 5.2.60618.0
For additional information, visit https://www.asp.net/

Azure App Service Tools v3.0.0 15.8.05023.0
Azure App Service Tools v3.0.0

Azure Functions and Web Jobs Tools 15.9.02046.0
Azure Functions and Web Jobs Tools

C# Tools 2.9.0-beta8-63208-01
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Common Azure Tools 1.10
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

Crystal Reports for .NET Framework
Crystal Reports for .NET Framework

Extensibility Message Bus 1.1.49 (remotes/origin/d15-8@ee674f3)
Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration.

GitHub.VisualStudio 2.5.8.5165
A Visual Studio Extension that brings the GitHub Flow into Visual Studio.

JavaScript Language Service 2.0
JavaScript Language Service

JavaScript Project System 2.0
JavaScript Project System

Microsoft Azure Tools 2.9
Microsoft Azure Tools for Microsoft Visual Studio 2017 - v2.9.10730.2

Microsoft Continuous Delivery Tools for Visual Studio 0.4
Simplifying the configuration of Azure DevOps pipelines from within the Visual Studio IDE.

Microsoft JVM Debugger 1.0
Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines

Microsoft Library Manager 1.0
Install client-side libraries easily to any web project

Microsoft MI-Based Debugger 1.0
Provides support for connecting Visual Studio to MI compatible debuggers

Microsoft Visual C++ Wizards 1.0
Microsoft Visual C++ Wizards

Microsoft Visual Studio Tools for Containers 1.1
Develop, run, validate your ASP.NET Core applications in the target environment. F5 your application directly into a container with debugging, or CTRL + F5 to edit & refresh your app without having to rebuild the container.

Microsoft Visual Studio VC Package 1.0
Microsoft Visual Studio VC Package

MLGen Package Extension 1.0
MLGen Package Visual Studio Extension Detailed Info

Mono Debugging for Visual Studio 4.11.11-pre (8fb558f)
Support for debugging Mono processes with Visual Studio.

NuGet Package Manager 4.6.0
NuGet Package Manager in Visual Studio. For more information about NuGet, visit http://docs.nuget.org/.

ProjectServicesPackage Extension 1.0
ProjectServicesPackage Visual Studio Extension Detailed Info

ResourcePackage Extension 1.0
ResourcePackage Visual Studio Extension Detailed Info

ResourcePackage Extension 1.0
ResourcePackage Visual Studio Extension Detailed Info

SQL Server Data Tools 15.1.61808.07020
Microsoft SQL Server Data Tools

SQL Server Reporting Services 15.0.900.163
Microsoft SQL Server Reporting Services Designers
Version 15.0.900.163

TypeScript Tools 15.8.20822.2001
TypeScript Tools for Microsoft Visual Studio

Visual Basic Tools 2.9.0-beta8-63208-01
Visual Basic components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Visual F# Tools 10.2 for F# 4.5 15.8.0.0. Commit Hash: 55a3dc3231c95c77f81ee53f7d29152029da7408.
Microsoft Visual F# Tools 10.2 for F# 4.5

Visual Studio Code Debug Adapter Host Package 1.0
Interop layer for hosting Visual Studio Code debug adapters in Visual Studio

Visual Studio Tools for Containers 1.0
Visual Studio Tools for Containers

Visual Studio Tools for Universal Windows Apps 15.0.28010.2046
The Visual Studio Tools for Universal Windows apps allow you to build a single universal app experience that can reach every device running Windows 10: phone, tablet, PC, and more. It includes the Microsoft Windows 10 Software Development Kit.

VisualStudio.Mac 1.0
Mac Extension for Visual Studio

Windows Template Studio 2.4.18260.1
Windows Template Studio quickly builds a UWP app, using a wizard-based UI to turn your needs into a foundation of Windows 10 patterns and best practices.

Xamarin 4.11.0.776 (d15-8@1ae9b59d7)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin Designer 4.15.9 (d000f568b)
Visual Studio extension to enable Xamarin Designer tools in Visual Studio.

Xamarin Live Reload 0.4.0 (remotes/origin/dev@75526a0)
Provides live reload capabilities for Xamarin XAML.

Xamarin Templates 1.1.116 (9619170)
Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms.

Xamarin.Android SDK 9.0.0.20 (HEAD/86d33f45b)
Xamarin.Android Reference Assemblies and MSBuild support.

Xamarin.iOS and Xamarin.Mac SDK 12.0.0.15 (84552a4)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

• Version with issue:
• Last known good version:
• IDE:
• Platform Target Frameworks:
  
  
  
  • iOS:
  
  
  • Android:
  
  
  • UWP:
  
  
• Android Support Library Version:
• Nuget Packages:
• Affected Devices:

Screenshots

Reproduction Link

[GalaxiaGuy]

I believe that syntax for OnPlatform is legacy, and as such did not get UWP support.

The correct way now would be something like the following:

<OnPlatform x:TypeArguments="x:Double">
    <OnPlatform.Platforms>
        <On Platform="iOS" Value="40" />
        <On Platform="Android" Value="40" />
        <On Platform="UWP" Value="40" />
    </OPllatform.Platforms>
</OnPlatform>

There is also a markup extension which reduces typing:

<Setter Property="FontSize" Value="{OnPlatform Android=40, iOS=40, UWP=40}"/>

but I'm not sure what version it was added in.

[pauldipietro]

You can refer to these docs.