ScrapySharp Form Submit causing System.AggregateException

Question

我花了几个小时绞尽脑汁为什么这不起作用

我正在尝试使用ScrapySharp来抓取网站，现在只是尝试示例网站，然后移动到我的实际网站。

每次我在程序中执行form.Submit()时，我都会遇到 System.AggregateException(指定的强制转换无效(

我的代码：

using System;
using System.IO;
using System.Linq;
using System.Net;
using HtmlAgilityPack;
using ScrapySharp.Extensions;
using ScrapySharp.Html;
using ScrapySharp.Html.Forms;
using ScrapySharp.Network;
namespace WebScraper
{
class MainClass
{
public static void Main(string[] args)
{
ScrapingBrowser browser = new ScrapingBrowser();
//set UseDefaultCookiesParser as false if a website returns invalid cookies format
//browser.UseDefaultCookiesParser = false;
browser.AllowAutoRedirect = true;
browser.AllowMetaRedirect = true;
WebPage homePage = browser.NavigateToPage(new Uri("http://the-internet.herokuapp.com/login"));
PageWebForm form = homePage.FindForm("login");
form["username"] = "tomsmith";
form["password"] = "SuperSecretPassword!";
form.Method = HttpVerb.Get; //I tried both .Post and .Get
WebPage resultsPage = form.Submit(); //THIS IS WHERE I GET THE ERROR
Console.WriteLine(resultsPage);
}
}
}

我的错误：

System.AggregateException：发生一个或多个错误。(指定的强制转换无效。---> System.InvalidCastException：指定的强制转换无效。 at ScrapySharp.Network.ScrapingBrowser.CreateRequest (System.Uri url， ScrapySharp.Network.HttpVerb verb( [0x0000b] in <0a639adc663f45108f057c429262c620>：0 at ScrapySharp.Network.ScrapingBrowser.NavigateToPageAsync (System.Uri url， ScrapySharp.Network.HttpVerb verb， System.String data， System.String contentType( [0x00066] in <0a639adc663f45108f057c429262c620>：0 ---内部异常堆栈跟踪结束--- at System.Threading.Tasks.Task.ThrowIfExceptional (System.Boolean includeTaskCanceledExceptions( [0x00011] in/Users/builder/jenkins/workspace/build-package-osx-mono/2019-06/external/bockbuild/builds/mono-x64/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs：2027 at System.Threading.Tasks.Task1[TResult].GetResultCore (System.Boolean waitCompletionNotification) [0x0002b] in /Users/builder/jenkins/workspace/build-package-osx-mono/2019-06/external/bockbuild/builds/mono-x64/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:496 at System.Threading.Tasks.Task1[TResult].get_Result (( [0x00000] in/Users/builder/jenkins/workspace/build-package-osx-mono/2019-06/external/bockbuild/builds/mono-x64/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs：466 at ScrapySharp.Network.ScrapingBrowser.NavigateToPage (System.Uri url， ScrapySharp.Network.HttpVerb verb， System.String data， System.String contentType( [0x0000b] in <0a639adc663f45108f057c429262c620>：0 at ScrapySharp.Html.Forms.PageWebForm.Submit (( [0x00023] in <0a639adc663f45108f057c429262c620>：0 at WebScraper.MainClass.Main (System.String[] args( [0x00065] in/Users/arib/Projects/WebScraper/WebScraper/Program.cs：29

我厌倦了这个错误，非常感谢任何和所有的帮助。 谢谢

Answer 1

问题是当你使用form["username"]时，结果是一个字符串。你想要获取FormField，你可以使用以下代码来做到这一点：

WebPage homePage = browser.NavigateToPage(new Uri("http://the-internet.herokuapp.com/login"));
PageWebForm form = homePage.FindForm("login");
var formFields = form.FormFields;
foreach (var field in formFields)
{
if (field.Name.Equals("username", StringComparison.OrdinalIgnoreCase))
{
field.Value = "tomsmith";
}
else if (field.Name.Equals("password", StringComparison.OrdinalIgnoreCase))
{
field.Value = "SuperSecretPassword!";
}
}
WebPage resultsPage = form.Submit();
Console.WriteLine(resultsPage);

或者，您可以使用Find()来获取FormField：

var usernameField = form.FormFields.Find(x => x.Name == "username");