Selenium RemoteWebDriver c# - System.InvalidOperationException


I have a sample UI test project using v3.4.0 of Selenium.WebDriver.

Everything works fine when I run the tests against a local driver but I want to get things working using Selenium Grid 2.

As soon as I try to instantiate a new RemoteWebDriver I get an exception with little detail.

Driver = new RemoteWebDriver(new Uri(GridUrl), Capabilities);     

Note: GridUrl is “http://localhost:4444/wd/hub

Throws a System.InvalidOperationException with StackTrace as follows:

   at OpenQA.Selenium.Remote.RemoteWebDriver.UnpackAndThrowOnError(Response errorResponse)
OpenQA.Selenium.Remote.RemoteWebDriver.Execute(String driverCommandToExecute, Dictionary`2 parameters)
OpenQA.Selenium.Remote.RemoteWebDriver.StartSession(ICapabilities desiredCapabilities)
OpenQA.Selenium.Remote.RemoteWebDriver..ctor(ICommandExecutor commandExecutor, ICapabilities desiredCapabilities)
OpenQA.Selenium.Remote.RemoteWebDriver..ctor(Uri remoteAddress, ICapabilities desiredCapabilities)
at xxxx
.Ui.Tests.SeleniumTests.TestInitialize() in C:\Users\xxxx\Documents\Visual Studio 2015\Projects\xxxx.Ui.Tests\xxxx.Tests\PersonTests.cs:line 38

Hub configuration

I have v3.4.0 of the hub running locally with the following configuration:

"port": 4444,
"newSessionWaitTimeout": -1,
"servlets" : [],
"withoutServlets": [],
"custom": {},
"throwOnCapabilityNotPresent": true,
"cleanUpCycle": 5000,
"role": "hub",
"debug": false,
"browserTimeout": 0,
"timeout": 1800

Hub started with:

java -jar selenium-server-standalone-3.4.0.jar -role hub

This has come up OK and looks to be running.
working hub console

Node configuration

I have tried a number of nodes (chromedriver.exe, IEDriverServer.exe and geckodrvier.exe). None of these work with the RemoteWebDriver. All of them are in a directory that has been added to my system PATH variable.

Chrome config

"browserName": "chrome",
"maxInstances": 5,
"seleniumProtocol": "WebDriver"
"proxy": "org.openqa.grid.selenium.proxy.DefaultRemoteProxy",
"maxSession": 5,
"port": 5556,
"register": true,
"registerCycle": 5000,
"hub": "http://localhost:4444",
"nodeStatusCheckTimeout": 5000,
"nodePolling": 5000,
"role": "node",
"unregisterIfStillDownAfter": 60000,
"downPollingLimit": 2,
"debug": false,
"servlets" : [],
"withoutServlets": [],
"custom": {}

Node started with:

java -jar selenium-server-standalone-3.4.0.jar -role node -nodeConfig chromeNodeConfig.json

The other node configs are largely the same except for the different browser names and ports.

Once all nodes are started, the console looks as follows:
console with nodes running

I’m not able to get much from the exception. Is it a versioning issue of the drivers I have? I have tried customising my DesiredCapabilities to ensure I’m matching those in the node config. All of that looks fine.


As requested I’m adding a bit more detail as to how I’m trying to launch a browser. None of the browsers work with the RemoteWebDriver whereas they do with the local drivers. Showing the Chrome example – only difference between each is regarding the Capabilities that I’m passing in to the base class constructor.

In my test class

public class PersonTests : PersonTestBase
public PersonTests()
: base(DesiredCapabilities.Chrome())
public void Chrome_ShouldCreatePlacement()

In my base class I am doing the following

public abstract class PersonTestBase
protected IWebDriver Driver;
protected ICapabilities Capabilities;
protected string TargetUrl;
protected string GridUrl;
protected PersonTests(ICapabilities capabilities)
this.Capabilities = capabilities;
public void TestInitialize()
TargetUrl = "http://urlOfMyWebsite";
GridUrl = "http://localhost:4444/wd/hub"
Driver = new RemoteWebDriver(new Uri(GridUrl), Capabilities);
public void TestCleanup()
protected void ShouldCreatePerson()
//rest of test code ommitted
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Downgrade to 3.3.0 until this issue gets resolved and a new release of Selenium Standalone Server is available (Recommended solution)


  1. Download the Solution
  2. Comment this line
  3. Build dotnet language bindings

    • Open command window in root directory
    • Run go //dotnet:release
    • And reference the binaries built in {root}/build/dotnet/dist

Note: This workaround does NOT fix anything! It ignores the piece of selenium grid code that causes failure.

Another note: Be aware that upgrading to Selenium 3.4 may require upgrading webdrivers as well

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