Selenium

Selenium reaches Chromium through ChromeDriver. ChromeDriver normally starts a browser of its own, but it can also attach to one that is already running and exposes a remote debugging endpoint over the Chrome DevTools Protocol, or CDP. That is how it connects to DotNetBrowser.

Read DevTools Protocol first for the rules that apply to every automation tool.

Prerequisites 

Reference two NuGet packages in the project that runs the test scenario:

• Selenium.WebDriver — the WebDriver API. The example uses 3.141.0, and the API shown here is unchanged in Selenium 4.
• Selenium.WebDriver.ChromeDriver — the ChromeDriver executable.

DotNetBrowser 4.3.0 is based on Chromium 152.0.7977.65, so use a Selenium.WebDriver.ChromeDriver package built for that release.

Enabling the endpoint 

Create the engine with a remote debugging port:

EngineOptions engineOptions = new EngineOptions.Builder
    {
        RemoteDebuggingPort = RemoteDebuggingPort
    }
   .Build();

engine = EngineFactory.Create(engineOptions);
browser = engine.CreateBrowser();

Dim engineOptionsBuilder As EngineOptions.Builder = new EngineOptions.Builder
With engineOptionsBuilder
    .RemoteDebuggingPort = RemoteDebuggingPort
End With

Dim engineOptions = engineOptionsBuilder.Build()

engine = EngineFactory.Create(engineOptions)
browser = engine.CreateBrowser()

RemoteDebuggingPort is the only engine option the connection needs.

Connecting the driver 

Point ChromeOptions.DebuggerAddress at the endpoint and create the driver:

ChromeOptions options = new ChromeOptions
{
    DebuggerAddress = RemoteDebuggingAddress
};

IWebDriver webDriver = new ChromeDriver(options)
{
    Url = StartPage
};

// Give FindElement time to wait for the page to load.
webDriver.Manage().Timeouts().ImplicitWait =
    TimeSpan.FromSeconds(10);

Dim options As ChromeOptions = new ChromeOptions
With options
    .DebuggerAddress = RemoteDebuggingAddress
End With

Dim webDriver As IWebDriver = new ChromeDriver(options)
With webDriver
    .Url = StartPage
End With

' Give FindElement time to wait for the page to load.
webDriver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(10)

DebuggerAddress takes a host and port, without a scheme. The port has to be the one the engine opened: the example sets RemoteDebuggingPort to 9222, so the driver connects to localhost:9222. When DebuggerAddress is set, ChromeDriver attaches to that endpoint instead of starting a browser.

Assigning Url navigates the page that is already open in the BrowserView control. The example points it at a page shipped alongside the application, so the scenario does not depend on an external site.

From there the element-level WebDriver API applies: FindElement, Click, SendKeys, and script execution all operate on the embedded browser. The implicit wait covers the navigation a click starts, so FindElement retries until the next page has loaded instead of failing on the first attempt.

Window commands are the exception. The window belongs to your application, not to ChromeDriver: switching to full screen fails outright, and the rest are not reliable. Size the BrowserView control from your application instead.

Threading and lifetime 

The example runs its scenario from the form Load handler, once the engine is up, and calls webDriver.Quit() when the scenario finishes.

WebDriver calls block, so run them off the UI thread and marshal any result back before touching controls. The example wraps the scenario in Task.Run and calls Invoke when it needs the form.

Troubleshooting 

A version mismatch between ChromeDriver and Chromium is the most common failure. ChromeDriver reports it as a session creation error naming both versions. Install the Selenium.WebDriver.ChromeDriver version named in Prerequisites.

If the connection is refused, check that the engine was created with RemoteDebuggingPort, that the port in DebuggerAddress is the same one, and that the engine is running when the driver connects. Trying 127.0.0.1 instead of localhost is also worth a moment.

The complete example is available in our repository: C#, VB.NET.