Receiving NullReferenceException on using container.Resolve(); Object reference not set to an instance of an object

Question

I am receiving NullReferenceException on CleanUp() method. The below code is from SpecflowHooks.cs

Driver code in SpecflowHooks

    public static ChromeDriver driver { get; set; }
[BeforeFeature]

public static void OneTime()

{
    ChromeOptions options = new ChromeOptions();
    options.AddArgument("--ignore-ssl-errors=yes");
    options.AddArgument("--ignore-certificate-errors");
    string Path = "D:/repos/Hoogly/Drivers/"; 
    driver = new ChromeDriver(Path);
    driver.Manage().Window.Maximize(); 
    driver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(30);

}

    private readonly IObjectContainer container;

    public SpecflowHooks(IObjectContainer container)
    {
        this.container = container;
    }        

[BeforeScenario]
    public void Setup()
    {
        container.RegisterInstanceAs(driver);
    }

[AfterScenario]
    public void CleanUp()
    {
        container.Resolve<IWebDriver>();
        driver.Close();
        driver.Dispose();

    }

While Debugging I noticed that the Container is blank when Cleanup() method is executed. But I am not clear as to why that is getting blank even after the Register Instance in Setup(). I am using Specflow and Selenium Webdriver I am not sure if this is the optimal way to manage drivers.

@JeroenvanLangen Edited the question text for better visibility — Eenie Meenie, Mar 17 '23 at 12:33
Does this answer your question? [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Mark Benningfield, Mar 17 '23 at 12:40
@MarkBenningfield It sure helps but doesn't answer the question. I already know why the exception is thrown, but don't know how to fix it. Exception is because container is null when container.Resolve line of code is executed. — Eenie Meenie, Mar 17 '23 at 17:38
Where does the `OneTime()` method get called? We are still missing code to see the full picture. — Greg Burghardt, Mar 20 '23 at 12:38
@GregBurghardt We have [BeforeFeature] added for OneTime() I updated that to the Question. — Eenie Meenie, Mar 20 '23 at 14:30
Are you sure `container` is null? Please post the full code for the class that contains the methods in your question. — Greg Burghardt, Mar 20 '23 at 17:18

score 0 · Answer 1 · answered Mar 20 '23 at 17:26

There are a number of problems with the code:

The call to container.RegisterInstanceAs passes the driver object, so it is registering the web driver as an instance of ChromeDriver. Change this to:
```
container.RegisterInstanceAs<IWebDriver>(driver);
//                          ^^^^^^^^^^^^
```
Do not dispose of the web driver after each scenario. The BeforeFeature hook executes once per feature. The AfterScenario hook executes multiple times per feature (once for each scenario in that feature file). If you create the web driver once per feature, dispose of it once per feature.
```
[AfterFeature]
public void CleanUp()
{
    driver.Close();
    driver.Dispose();
}
```

The full class should look like:

[Binding]
public class SpecflowHooks
{
    public static ChromeDriver driver { get; set; }

    private readonly IObjectContainer container;

    public SpecflowHooks(IObjectContainer container)
    {
        this.container = container;
    }        

    [BeforeFeature]
    public static void OneTime()
    {
        ChromeOptions options = new ChromeOptions();
        options.AddArgument("--ignore-ssl-errors=yes");
        options.AddArgument("--ignore-certificate-errors");
        string Path = "D:/repos/Hoogly/Drivers/"; 
        driver = new ChromeDriver(Path);
        driver.Manage().Window.Maximize(); 
        driver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(30);
    }

    [BeforeScenario]
    public void Setup()
    {
        container.RegisterInstanceAs<IWebDriver>(driver);
    }

    [AfterFeature]
    public static void CleanUp()
    {
        driver.Close();
        driver.Dispose();
    }
}

Receiving NullReferenceException on using container.Resolve(); Object reference not set to an instance of an object

1 Answers1