Essentials: [Bug] Calling Launcher. TryOpenAsync(string uri) causes exception

[mbalous]

Description

Steps to Reproduce

1. Invoke this code

string email = "[email protected]";
await Device.InvokeOnMainThreadAsync(() => Launcher.TryOpenAsync($"mailto:{email}"));

Expected Behavior

No exception is beign thrown

Actual Behavior

Exception System.InvalidOperationException with message _'A method was called at an unexpected time.'_ is thrown

Basic Information

• Version with issue: 1.3.1 & 1.5.1
• IDE: VS 2019
• Platform Target Frameworks:
  
  
  
  • UWP: Windows 10, version 1809 (10.0; Build 17763)
  
  

Screenshots

[jamesmontemagno]

I am unable to reproduce this with your code. can you please provide a sample.

[mbalous]

Go to TrackerViewModel.MailTo(object obj) to see the command executed (or place breakpoint). Execute command by launching the application and pressing the button _"Open email uri"_

Executed code on button press:

private async void MailTo(object obj)
{
    string email = "[email protected]";
    await Device.InvokeOnMainThreadAsync(() => Xamarin.Essentials.Launcher.TryOpenAsync($"mailto:{email}"));
}

Sample.zip

.csproj

<TargetPlatformVersion>10.0.18362.0</TargetPlatformVersion>
<TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
.
.
.
<PackageReference Include="Xamarin.Forms" Version="4.5.0.356" />
<PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform" Version="6.2.9" />
<PackageReference Include="Xamarin.Essentials" Version="1.5.1" />

[jamesmontemagno]

I was able to reproduce your issue.

Calling "OpenAsync" works fine, however "TryOpenAsync" does not.

Workaround:'

private async void MailTo(object obj)
        {
            string email = "[email protected]";
            if (await Xamarin.Essentials.Launcher.CanOpenAsync("mailto:"))
                await Xamarin.Essentials.Launcher.OpenAsync($"mailto:{email}");
        }

You do not need to invoke on the main thread as it is coming from a command in which it already is on the main thread :)

[jamesmontemagno]

Hmmm strange. it only seems to be an issue when targeting newer versions of UWP which is why we didn't catch it.

[mbalous]

You do not need to invoke on the main thread as it is coming from a command in which it already is on the main thread :)

Thank you, I'm aware of that, but in order to try fixing this error, I tried various approaches.
Nevertheless, thanks for suggesting the workaround.

[maexsp]

Workaround with subject and body (unfortionatly only plaintext on android possible). This opens less non-email related apps to send an email (if using e.g. Email.ComposeAsync(...) )
if (await Launcher.CanOpenAsync(new Uri("mailto:"))) { await Launcher.OpenAsync($"mailto:{emailTo}?subject={subject}&body={body}"); } else { await Email.ComposeAsync(subject, body, new []{ emailTo }); }

[Redth]

Fixed in #1171