sharee.bike-App/LockIt.BLE/Services/BluetoothLock/StateChecker.cs

using System;
using System.Threading.Tasks;
using Plugin.BLE.Abstractions.Contracts;

namespace ShareeBike.Services.BluetoothLock
{
	public static class StateChecker
	{
		/// <summary>
		/// Get current bluetooth state
		/// </summary>
		/// <remarks>See https://github.com/xabre/xamarin-bluetooth-le/issues/112#issuecomment-380994887.</remarks>
		/// <param name="ble">Crossplatform bluetooth implementation object</param>
		/// <returns>BluetoothState</returns>
		public static Task<BluetoothState> GetBluetoothState(this IBluetoothLE ble)
		{
			var tcs = new TaskCompletionSource<BluetoothState>();

			if (ble.State != BluetoothState.Unknown)
			{
				// If we can detect state out of box just returning in
				tcs.SetResult(ble.State);
			}
			else
			{
				// Otherwise let's setup dynamic event handler and wait for first state update
				EventHandler<Plugin.BLE.Abstractions.EventArgs.BluetoothStateChangedArgs> handler = null;
				handler = (o, e) =>
				{
					ble.StateChanged -= handler;
					// and return it as our state
					// we can have an 'Unknown' check here, but in normal situation it should never occur
					tcs.SetResult(e.NewState);
				};
				ble.StateChanged += handler;
			}

			return tcs.Task;
		}
	}
}