javascript - C# Cefsharp unable to getElementsByClassName - Stack Overflow

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I am trying to read text from elements by class name in cefsharp. This code from @Jim W does a similar task, only it uses ID instead of class

private void button1_Click(object sender, EventArgs e)
    {

        string EvaluateJavaScriptResult;
        var frame = chromeBrowser.GetMainFrame();
        var task = frame.EvaluateScriptAsync("(function() { return document.getElementById('searchInput').value; })();", null);

        task.ContinueWith(t =>
        {
            if (!t.IsFaulted)
            {
                var response = t.Result;
                EvaluateJavaScriptResult = response.Success ? (response.Result.ToString() ?? "null") : response.Message;
                MessageBox.Show(EvaluateJavaScriptResult);
            }
        }, TaskScheduler.FromCurrentSynchronizationContext());





    }

Upon changing string EvaluateJavaScriptResult; to obj EvaluateJavaScriptResult; and document.getElementById to document.getElementsByClassNameand providing the class name as well as the index, I get error: "Uncaught SyntaxError: missing ) after argument list @:1:53" as the return result. I cannot find where the missing ) is and I have tried lots of different placements of ( and ) in many places and I don't think this is the real error anymore. Everything I have tried has still given me the error @:1:53 (the location?) and I think that means its erroring before it attempts to look for the class name. Does anyone know how I can successfully make cefsharp return the text value of something found by classname?

Edit: upon running a copy and pasted selection of the code I am referencing here, I actually get a different problem, now it just returns null. (This really should just be the same code)

this is the code that returns null

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using CefSharp;
using CefSharp.WinForms;

namespace WebAppWorkAround
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        InitializeChromium();
    }
    List<string> classList = new List<string>();
    public ChromiumWebBrowser chromeBrowser;

    private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
    {

    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }
    private void InitializeChromium()
    {
        CefSettings settings = new CefSettings();
        Cef.Initialize(settings);
        chromeBrowser = new ChromiumWebBrowser("");
        this.panel1.Controls.Add(chromeBrowser);
        chromeBrowser.Dock = DockStyle.Fill;

    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        Cef.Shutdown();
    }
    public string extract;

    private void button1_Click(object sender, EventArgs e)
    {

        object EvaluateJavaScriptResult;
        var frame = chromeBrowser.GetMainFrame();
        var task = frame.EvaluateScriptAsync("(function() { return document.getElementsByClassName('mw-headline')[0].value; })();", null);

        task.ContinueWith(t =>
        {
            if (!t.IsFaulted)
            {
                var response = t.Result;
                EvaluateJavaScriptResult = response.Success ? (response.Result ?? "null") : response.Message;
                MessageBox.Show(EvaluateJavaScriptResult.ToString());
            }
        }, TaskScheduler.FromCurrentSynchronizationContext());





    }


}
}

I am trying to read text from elements by class name in cefsharp. This code from @Jim W does a similar task, only it uses ID instead of class

private void button1_Click(object sender, EventArgs e)
    {

        string EvaluateJavaScriptResult;
        var frame = chromeBrowser.GetMainFrame();
        var task = frame.EvaluateScriptAsync("(function() { return document.getElementById('searchInput').value; })();", null);

        task.ContinueWith(t =>
        {
            if (!t.IsFaulted)
            {
                var response = t.Result;
                EvaluateJavaScriptResult = response.Success ? (response.Result.ToString() ?? "null") : response.Message;
                MessageBox.Show(EvaluateJavaScriptResult);
            }
        }, TaskScheduler.FromCurrentSynchronizationContext());





    }

Upon changing string EvaluateJavaScriptResult; to obj EvaluateJavaScriptResult; and document.getElementById to document.getElementsByClassNameand providing the class name as well as the index, I get error: "Uncaught SyntaxError: missing ) after argument list @:1:53" as the return result. I cannot find where the missing ) is and I have tried lots of different placements of ( and ) in many places and I don't think this is the real error anymore. Everything I have tried has still given me the error @:1:53 (the location?) and I think that means its erroring before it attempts to look for the class name. Does anyone know how I can successfully make cefsharp return the text value of something found by classname?

Edit: upon running a copy and pasted selection of the code I am referencing here, I actually get a different problem, now it just returns null. (This really should just be the same code)

this is the code that returns null

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using CefSharp;
using CefSharp.WinForms;

namespace WebAppWorkAround
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        InitializeChromium();
    }
    List<string> classList = new List<string>();
    public ChromiumWebBrowser chromeBrowser;

    private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
    {

    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }
    private void InitializeChromium()
    {
        CefSettings settings = new CefSettings();
        Cef.Initialize(settings);
        chromeBrowser = new ChromiumWebBrowser("https://en.wikipedia/wiki/Main_Page");
        this.panel1.Controls.Add(chromeBrowser);
        chromeBrowser.Dock = DockStyle.Fill;

    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        Cef.Shutdown();
    }
    public string extract;

    private void button1_Click(object sender, EventArgs e)
    {

        object EvaluateJavaScriptResult;
        var frame = chromeBrowser.GetMainFrame();
        var task = frame.EvaluateScriptAsync("(function() { return document.getElementsByClassName('mw-headline')[0].value; })();", null);

        task.ContinueWith(t =>
        {
            if (!t.IsFaulted)
            {
                var response = t.Result;
                EvaluateJavaScriptResult = response.Success ? (response.Result ?? "null") : response.Message;
                MessageBox.Show(EvaluateJavaScriptResult.ToString());
            }
        }, TaskScheduler.FromCurrentSynchronizationContext());





    }


}
}

• javascript
• c#
• automation
• chromium
• cefsharp

Share Improve this question Follow edited Jun 18, 2018 at 18:00 SJ10 asked Jun 14, 2018 at 18:42 SJ10SJ10 33511 gold badge55 silver badges1313 bronze badges 3

• You need to show the code that doesn't work, even though you've explained what change you made, we need to see it as it is in your file. – Jim W Commented Jun 14, 2018 at 21:04
• I was about to add this to the question when I realized that after replicating the code I get a different error. I'm at a loss for an explanation, because i copy and pasted the same code from before. Ill get back to you on this when possible. – SJ10 Commented Jun 15, 2018 at 21:10
• @Jim W I have updated the question. – SJ10 Commented Jun 18, 2018 at 18:00

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1 Answer 1

Sorted by: Reset to default 5

What element is mw-headline, does that have a .value property? Probably not, given what's happening.

Assuming that mw-headline is an element like DIV or SPAN, you can use

var task = frame.EvaluateScriptAsync("(function() { return document.getElementsByClassName('mw-headline')[0].innerText; })();", null);

This works because value is for text boxes and input fields, whereas static markup elements like DIV have innerText and innerHTML.

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