Trying to get a screenshot of the browser page using cefsharp but getting exceptions. how to take a screenshot?

Question

In the file MainWindow.xaml.cs in the method TakeScreenShot i'm getting exception on the line :

var executedScript = WebView.EvaluateScriptAsync(jsString).Result.Result;

System.Exception HResult=0x80131500 Message=Unable to execute javascript at this time, scripts can only be executed within a V8Context. Use the IWebBrowser.CanExecuteJavascriptInMainFrame property to guard against this exception. See https://github.com/cefsharp/CefSharp/wiki/General-Usage#when-can-i-start-executing-javascript for more details on when you can execute javascript. For frames that do not contain Javascript then no V8Context will be created. Executing a script once the frame has loaded it's possible to create a V8Context. You can use browser.GetMainFrame().ExecuteJavaScriptAsync(script) or browser.GetMainFrame().EvaluateScriptAsync to bypass these checks (advanced users only). Source=CefSharp StackTrace: at CefSharp.WebBrowserExtensions.ThrowExceptionIfCanExecuteJavascriptInMainFrameFalse() at CefSharp.WebBrowserExtensions.EvaluateScriptAsync(IChromiumWebBrowserBase browser, String script, Nullable`1 timeout, Boolean useImmediatelyInvokedFuncExpression) at Web_Browser_WPF.MainWindow.TakeScreenShot(String siteUrl) in D:\Csharp Projects\Web Browser WPF\MainWindow.xaml.cs:line 47 at Web_Browser_WPF.MainWindow.ChromiumWebBrowser_LoadingStateChanged(Object sender, LoadingStateChangedEventArgs e) in D:\Csharp Projects\Web Browser WPF\MainWindow.xaml.cs:line 64 at CefSharp.Wpf.ChromiumWebBrowser.CefSharp.Internals.IWebBrowserInternal.SetLoadingStateChange(LoadingStateChangedEventArgs args) at CefSharp.Internals.ClientAdapter.OnLoadingStateChange(ClientAdapter* , scoped_refptr* browser, Boolean isLoading, Boolean canGoBack, Boolean canGoForward)

and then if i mark as comment not to use the part of the jString and executedScript and not assigning to the height then i'm getting null exception on the line :

bitmap.Save(@"d:\Test.jpg");

because WebView is null.

so i'm stuck here.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using CefSharp;
using CefSharp.OffScreen;

namespace Web_Browser_WPF
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            WindowStartupLocation = 
                System.Windows.WindowStartupLocation.CenterScreen;
        }

        private void TakeScreenShot(string siteUrl)
        {
            CefSharp.OffScreen.ChromiumWebBrowser WebView = new CefSharp.OffScreen.ChromiumWebBrowser(siteUrl);

            int width = 1280;
            int height = 1480;

            string jsString = "Math.max(document.body.scrollHeight, " +
                              "document.documentElement.scrollHeight, document.body.offsetHeight, " +
                              "document.documentElement.offsetHeight, document.body.clientHeight, " +
                              "document.documentElement.clientHeight);";


            var executedScript = WebView.EvaluateScriptAsync(jsString).Result.Result;

            height = Convert.ToInt32(executedScript);

            WebView.Size = new System.Drawing.Size(width, height); //size;

            Thread.Sleep(500);
            // Wait for the screenshot to be taken.
            var bitmap = WebView.ScreenshotOrNull();
            bitmap.Save(@"d:\Test.jpg");
            bitmap.Dispose();
        }

        private void ChromiumWebBrowser_LoadingStateChanged(object sender, LoadingStateChangedEventArgs e)
        {
            if(!e.IsLoading)
            {
                TakeScreenShot("https://ims.gov.il/he/RadarSatellite");
            }
        }
    }
}

The xaml code

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:cef="clr-namespace:Web_Browser_WPF"
        xmlns:Wpf="clr-namespace:CefSharp.Wpf;assembly=CefSharp.Wpf" x:Class="Web_Browser_WPF.MainWindow"
        mc:Ignorable="d"
        Title="MainWindow" Height="720" Width="1024">
    <Grid>

        <Wpf:ChromiumWebBrowser HorizontalAlignment="Left" Margin="363,181,0,0" VerticalAlignment="Top"/>
        <Wpf:ChromiumWebBrowser x:Name="chromiumBrowser1"/>
        <Wpf:ChromiumWebBrowser Address="https://ims.gov.il/he/RadarSatellite" LoadingStateChanged="ChromiumWebBrowser_LoadingStateChanged" />

    </Grid>
</Window>