Добавьте файлы проекта.

src/Massenger.Client/Platforms/Android/AndroidTaskExtensions.cs

@@ -0,0 +1,40 @@
+using Android.Gms.Tasks;
+
+namespace Massenger.Client;
+
+internal static class AndroidTaskExtensions
+{
+    public static Task<string?> AsStringAsync(this Android.Gms.Tasks.Task task, System.Threading.CancellationToken cancellationToken = default)
+    {
+        var taskCompletionSource = new TaskCompletionSource<string?>(TaskCreationOptions.RunContinuationsAsynchronously);
+        if (cancellationToken.CanBeCanceled)
+        {
+            cancellationToken.Register(() => taskCompletionSource.TrySetCanceled(cancellationToken));
+        }
+
+        task.AddOnCompleteListener(new TaskCompletionListener(taskCompletionSource));
+        return taskCompletionSource.Task;
+    }
+
+    private sealed class TaskCompletionListener(TaskCompletionSource<string?> taskCompletionSource)
+        : Java.Lang.Object,
+          IOnCompleteListener
+    {
+        public void OnComplete(Android.Gms.Tasks.Task task)
+        {
+            if (task.IsCanceled)
+            {
+                taskCompletionSource.TrySetCanceled();
+                return;
+            }
+
+            if (!task.IsSuccessful)
+            {
+                taskCompletionSource.TrySetException(new InvalidOperationException(task.Exception?.Message ?? "Android task failed."));
+                return;
+            }
+
+            taskCompletionSource.TrySetResult(task.Result?.ToString());
+        }
+    }
+}