MediaService.cs

[assembly: Xamarin.Forms.Dependency(typeof(MediaService))]
namespace SelectMultiIpleImagesApp.Droid
{
	public class MediaService : Java.Lang.Object, IMediaService
	{
		public async Task OpenGallery()
		{
			try
			{
				var status = await CrossPermissions.Current.CheckPermissionStatusAsync(Plugin.Permissions.Abstractions.Permission.Storage);
				if (status != PermissionStatus.Granted)
				{
					if (await CrossPermissions.Current.ShouldShowRequestPermissionRationaleAsync(Plugin.Permissions.Abstractions.Permission.Storage))
					{
						Toast.MakeText(Xamarin.Forms.Forms.Context, "Need Storage permission to access to your photos.", ToastLength.Long).Show();
					}

					var results = await CrossPermissions.Current.RequestPermissionsAsync(new[] { Plugin.Permissions.Abstractions.Permission.Storage });
					status = results[Plugin.Permissions.Abstractions.Permission.Storage];
				}

				if (status == PermissionStatus.Granted)
				{
					Toast.MakeText(Xamarin.Forms.Forms.Context, "Select max 20 images", ToastLength.Long).Show();
					var imageIntent = new Intent(
						Intent.ActionPick);
					imageIntent.SetType("image/*");
					imageIntent.PutExtra(Intent.ExtraAllowMultiple, true);
					imageIntent.SetAction(Intent.ActionGetContent);
					((Activity)Forms.Context).StartActivityForResult(
						Intent.CreateChooser(imageIntent, "Select photo"), MainActivity.OPENGALLERYCODE);

				}
				else if (status != PermissionStatus.Unknown)
				{
					Toast.MakeText(Xamarin.Forms.Forms.Context, "Permission Denied. Can not continue, try again.", ToastLength.Long).Show();
				}
			}
			catch (Exception ex)
			{
				Console.WriteLine(ex.ToString());
				Toast.MakeText(Xamarin.Forms.Forms.Context, "Error. Can not continue, try again.", ToastLength.Long).Show();
			}
		}
		
	
	}
}