As mentioned here, you need to check the driver is null.
//******************************************************************************
//
// Copyright (c) 2017 Microsoft Corporation. All rights reserved.
//
// This code is licensed under the MIT License (MIT).
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//******************************************************************************
using Microsoft.VisualStudio.TestTools.UnitTesting;
using OpenQA.Selenium.Appium.Windows;
using OpenQA.Selenium.Remote;
using System;
namespace CalculatorTest
{
public class CalculatorSession
{
// Note: append /wd/hub to the URL if you're directing the test at Appium
private const string WindowsApplicationDriverUrl = "http://127.0.0.1:4723";
private const string CalculatorAppId = "Microsoft.WindowsCalculator_8wekyb3d8bbwe!App";
protected static WindowsDriver<WindowsElement> session;
public static void Setup(TestContext context)
{
// Launch Calculator application if it is not yet launched
if (session == null)
{
// Create a new session to bring up an instance of the Calculator application
// Note: Multiple calculator windows (instances) share the same process Id
DesiredCapabilities appCapabilities = new DesiredCapabilities();
appCapabilities.SetCapability("app", CalculatorAppId);
appCapabilities.SetCapability("deviceName", "WindowsPC");
session = new WindowsDriver<WindowsElement>(new Uri(WindowsApplicationDriverUrl), appCapabilities);
Assert.IsNotNull(session);
// Set implicit timeout to 1.5 seconds to make element search to retry every 500 ms for at most three times
session.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(1.5);
}
}
public static void TearDown()
{
// Close the application and delete the session
if (session != null)
{
session.Quit();
session = null;
}
}
}
}