c# - 使用 selenium 读取浏览器日志时出现 System.NullReferenceException

Question

我正在使用 C#、selenium chromeWebDriver 编写。当我尝试使用 selenium 读取浏览器控制台日志文件时，我得到:

System.NullReferenceException: 'Object reference not set to an instance of an object.'

private void button1_Click(object sender, EventArgs e)
{
    ChromeOptions options = new ChromeOptions();
    options.SetLoggingPreference(LogType.Browser, LogLevel.Warning);
    IWebDriver driver = new ChromeDriver(options);

    driver.Url = "https://www.google.com/";

    var entries = driver.Manage().Logs.GetLog(LogType.Browser); // System.NullReferenceException
    foreach (var entry in entries)
    {
        Console.WriteLine(entry.ToString());
    }
}

Answer 1

这是我在 Selenium 4 推出之前的解决方案(也适用于 Selenium 4)。它快速而肮脏，旨在演示如何完成。随意更改和改进。

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using OpenQA.Selenium;
using OpenQA.Selenium.Chrome;
using OpenQA.Selenium.Remote;
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Reflection;
using System.Text;

namespace GetChromeConsoleLog
{
    internal static class Program
    {
        private static void Main()
        {
            // setup options
            var options = new ChromeOptions();
            options.SetLoggingPreference(LogType.Browser, LogLevel.All);

            // do whatever actions
            var driver = new ChromeDriver(options)
            {
                Url = "https://www.yahoo.com/"
            };

            var logs = driver.GetBrowserLogs();

            // extract logs (using the extension method GetBrowserLogs)
            foreach (var log in driver.GetBrowserLogs())
            {
                Console.WriteLine($"{log["timestamp"]}: {log["message"]}");
            }

            // cleanup
            driver.Dispose();

            // hold console
            Console.WriteLine();
            Console.WriteLine("Press any key to exit...");
            Console.ReadLine();
        }
    }

    public static class WebDriverExtensions
    {
        public static IEnumerable<IDictionary<string, object>> GetBrowserLogs(this IWebDriver driver)
        {
            // not a chrome driver
            if(driver.GetType() != typeof(ChromeDriver))
            {
                return Array.Empty<IDictionary<string, object>>();
            }

            // setup
            var endpoint = GetEndpoint(driver);
            var session = GetSession(driver);
            var resource = $"{endpoint}session/{session}/se/log";
            const string jsonBody = @"{""type"":""browser""}";

            // execute
            using (var httpClient = new HttpClient())
            {
                var content = new StringContent(jsonBody, Encoding.UTF8, "application/json");
                var response = httpClient.PostAsync(resource, content).GetAwaiter().GetResult();
                var responseBody = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
                return AsLogEntries(responseBody);
            }
        }

        private static string GetEndpoint(IWebDriver driver)
        {
            // setup
            const BindingFlags Flags = BindingFlags.Instance | BindingFlags.NonPublic;

            // get RemoteWebDriver type
            var remoteWebDriver = GetRemoteWebDriver(driver.GetType());

            // get this instance executor > get this instance internalExecutor
            var executor = remoteWebDriver.GetField("executor", Flags).GetValue(driver) as ICommandExecutor;

            // get URL
            var uri = executor.GetType().GetField("remoteServerUri", Flags).GetValue(executor) as Uri;

            // result
            return uri.AbsoluteUri;
        }

        private static Type GetRemoteWebDriver(Type type)
        {
            if (!typeof(RemoteWebDriver).IsAssignableFrom(type))
            {
                return type;
            }

            while (type != typeof(RemoteWebDriver))
            {
                type = type.BaseType;
            }

            return type;
        }

        private static SessionId GetSession(IWebDriver driver)
        {
            if (driver is IHasSessionId id)
            {
                return id.SessionId;
            }
            return new SessionId($"gravity-{Guid.NewGuid()}");
        }

        private static IEnumerable<IDictionary<string, object>> AsLogEntries(string responseBody)
        {
            // setup
            var value = $"{JToken.Parse(responseBody)["value"]}";
            return JsonConvert.DeserializeObject<IEnumerable<Dictionary<string, object>>>(value);
        }
    }
}

get logs