C# CefSharp RenderProcessMessageHandler example

April 3, 2022

I am a novice at C# and learning Cefsharp + javascript. I’m attempting to wait until the page has finished loading with Cefsharp to execute my code. I found code snippet below, and added that to a new class, in the class occurs errors about to creating interfaces, please help what need to write inside these interfaces?

public class RenderProcessMessageHandler : IRenderProcessMessageHandler
{
  // Wait for the underlying `Javascript Context` to be created, this is only called for the main frame.
  // If the page has no javascript, no context will be created.
  void IRenderProcessMessageHandler.OnContextCreated(IWebBrowser browserControl, IBrowser browser, IFrame frame)
  {
    const string script = "document.addEventListener('DOMContentLoaded', function(){ alert('DomLoaded'); });";

    frame.ExecuteJavaScriptAsync(script);
  }
}

this is photo of error

>Solution :

You need to implement all methods in the interface IRenderProcessMessageHandler

public class RenderProcessMessageHandler : IRenderProcessMessageHandler
{
  // Wait for the underlying `Javascript Context` to be created, this is only called for the main frame.
  // If the page has no javascript, no context will be created.
  void IRenderProcessMessageHandler.OnContextCreated(IWebBrowser browserControl, IBrowser browser, IFrame frame)
  {
    const string script = "document.addEventListener('DOMContentLoaded', function(){ alert('DomLoaded'); });";

    frame.ExecuteJavaScriptAsync(script);
  }

void IRenderProcessMessageHandler.OnFocusedNodeChanged(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IDomNode node)
        {
            var message = node == null ? "lost focus" : node.ToString();

            Console.WriteLine("OnFocusedNodeChanged() - " + message);
        }
  
  void IRenderProcessMessageHandler.OnContextReleased(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame)
        {
            //The V8Context is about to be released, use this notification to cancel any long running tasks your might have
        }

        void IRenderProcessMessageHandler.OnUncaughtException(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, JavascriptException exception)
        {
            Console.WriteLine("OnUncaughtException() - " + exception.Message);
        }
}

You can check this out for the reference