Sometimes it is useful for an app to launch at login. While a user can always accomplish this in the system preferences, having the possibility to turn on auto-launching inside the app is better.This tutorial will show how. This tutorial is based on this one but is more detailed and Xamarin-oriented.

First of all, we will need to create a solution with two projects. First one will be our primary application and the second one will be a helper app. Why do we need a helper? Cause Apple told us to do so.

Then we will enable sandboxing for both our apps.

Main app

For some reason, Xamarin decided not to add SMLoginItemSetEnabled function to the framework but we can easily do that!

public class StartAtLoginOption
{
    [DllImport("/System/Library/Frameworks/ServiceManagement.framework/ServiceManagement")]
    static extern bool SMLoginItemSetEnabled(IntPtr aId, bool aEnabled);


    public static bool StartAtLogin(bool value)
    {
        CoreFoundation.CFString id = new CoreFoundation.CFString("my.helper.app.bundle.id");
        return SMLoginItemSetEnabled(id.Handle, value);
    }
}

In your main app’s Main.storyboard file, add a Check Box Button to the Window, connect the ViewController’s action with OnLaunchAtStartupChanged method. Your main app’s window could now look like this:
Add action implementation to your ViewController class:

partial void OnLaunchAtStartupChanged(NSButton sender)
{
    StartAtLoginOption.StartAtLogin(sender.State == NSCellStateValue.On);
}

Helper app

Helper app should be marked as either Background only app (LSBackgroundOnly) or as Agent (LSUIElement).As we don’t want our helper app to show any UI double click on the Main.storyboard and in Xcode uncheck the “Is Initial Controller” box on Window Controller.

In the helper app, add these lines of code. We need to check if the main app is already running because the helper app will be launched every time we set up the login item via the SMLoginItemSetEnabled function in the main app.

public override void DidFinishLaunching(NSNotification notification)
{
    if (!NSWorkspace.SharedWorkspace.RunningApplications.Any(a => a.BundleIdentifier == "my.main.app.bundle.id"))
    {
        var path = new NSString(NSBundle.MainBundle.BundlePath)
            .DeleteLastPathComponent()
            .DeleteLastPathComponent()
            .DeleteLastPathComponent()
            .DeleteLastPathComponent();
        var pathToExecutable = path + @"Contents/MacOS/LoginItemTestMain";

        if (NSWorkspace.SharedWorkspace.LaunchApplication(pathToExecutable)) { }
        else NSWorkspace.SharedWorkspace.LaunchApplication(path);
    }

    NSApplication.SharedApplication.Terminate(this);

}

Building the app

Now we need to assemble the app. Not having all those nice things Xcode gives to native developers we will have to apply some third-party tools. I prefer to use Cake build which is always a good choice when you develop a Xamarin application.

The code is very simple here. After building the solution we need to place our helper app in Contents/Library/LoginItems folder of the main application package in the Artefacts task.

var target = Argument("target", "Default");
var configuration = Argument("configuration", "Debug");


Task("Restore-NuGet-Packages")
    .Does(() =>
{
    NuGetRestore("./LoginItemTest.sln");
});

Task("Build")
    .IsDependentOn("Restore-NuGet-Packages")
	  .Does (() =>
{
	DotNetBuild("./LoginItemTest.sln", c => c.Configuration = configuration);
});

Task("Artefacts")
    .IsDependentOn("Build")
	  .Does (() =>
{
    CleanDirectories("./Artefacts");
    CopyDirectory("./LoginItemTestMain/bin/" + configuration + "/LoginItemTestMain.app", "./Artefacts/LoginItemTestMain.app");
    CopyDirectory("./LoginItemTestHelper/bin/" + configuration + "/LoginItemTestHelper.app", "./Artefacts/LoginItemTestMain.app/Contents/Library/LoginItems/LoginItemTestHelper.app");
});

Task("Default")
    .IsDependentOn("Artefacts");

RunTarget (target);

Now build the app and copy it to your /Applications folder. Start the app, turn on launch at login and log out. Then, log in again and your main app will be launched. Keep in mind that this approach will only work if your app is located either in /Applications or ~/Applications, so for testing, you’ll have to copy your app to this location.

Sample project can be found here.