How to use PostMessage and BindObjectAsync in the same function

[phuocminh6464]

I have a button on web and when clicking it will send data to my WPF app. What I want is after processing with that data, WPF will send result to web. Currently, I use CefSharp.PostMessage to push message from web to WPF and handler JavascriptMessageReceived event to received message. Then I use that data to calculate and register JavascriptObjectRepository to send result to web after process ending. But the app always get error Uncaught (in promise) ReferenceError: bindingObj is not defined in JS at var result= bindingObj.getResult(); when I click button in web. Anyone has solution? Thanks
Note: I use Cefsharp ver 109.1.100 and net7

var isBound = web.JavascriptObjectRepository.IsBound("bindingObj");
if (isBound)
{
     web.JavascriptObjectRepository.UnRegister("bindingObj");
}
web.JavascriptObjectRepository.Register("bindingObj", new JavaScriptInteractionObj(), options: BindingOptions.DefaultBinder);

async function doAction() {
            CefSharp.PostMessage({ "Type": "key", "Value": "value"});

            CefSharp.DeleteBoundObject("bindingObj");
            CefSharp.RemoveObjectFromCache("bindingObj");
            await CefSharp.BindObjectAsync("bindingObj");

            var result= bindingObj.getResult();
            result.then((value) => {
                console.log(value);
            });
        }

[amaitland]

Then I use that data to calculate and register JavascriptObjectRepository to send result to web after process ending

Registering an object is expensive and is not really meant to be used in a dynamic register/unregister fashion. There's caching in the render process for performance reasons. I'd suggest using ResolveObject event to instead. Just register your object once.

Without a complete example it's impossible to know what's going on.

How to use PostMessage and BindObjectAsync in the same function

Whilst you can, you typically wouldn't mix and match.

For PostMessage you typically would pass a javascript function in as a param, you'll get a IJavascriptCallback in your c# code which you can use to async execute the JS function.

There's a basic example at #2775 (comment) and a unit tests at https://github.com/cefsharp/CefSharp/blob/master/CefSharp.Test/PostMessage/PostMessageTests.cs#L39

[phuocminh6464]

Hi @amaitland, thanks for your reply but I have more concern

What I want is: Using PostMessage in js function and receiveing message at JavascriptMessageReceived event in C# code. Then check if (type == "CheckPrinter"), WPF app will async execute the responseFunc JS function to post message for printing. When receiving message with "Type": "Print", WPF will call print function and send result to web after printing. I want web can automatic get that result immediately after printing finished.
JS FUNCTION

let responseFunc = function () {
                CefSharp.PostMessage({
                    "Type": "Print", Value: {
                        StampList: [{ "ID": "123", "Name": "Name1", "Status": "Not yet" },
                        { "ID": "456", "Name": "Name 2", "Status": "Not yet" }]
                    }
                });
            };
CefSharp.PostMessage({ "Type": "CheckPrinter", "Value": false, "Callback": responseFunc });

C# CODE

private async void OnBrowserJavascriptMessageReceived(object sender, JavascriptMessageReceivedEventArgs e)
        {
            var msg = e.ConvertMessageTo<PostMessageCallBack>();
            var callback = msg.Callback;
            var type = msg.Type;
            var value = msg.Value;

            if (type == "CheckPrinter")
            {              
                  // Do check printer connection
                  // If Printer connection is good
                  if (isConnected)
                  {
                       //Call a javascript function
                       var response = await callback.ExecuteAsync();
                       var success = response.Success; // true
                       var result = response.Result; // null
                       var mess = response.Message; // null

                       // Here can not get new message!!!
                       dynamic msgCallBack = e.ConvertMessageTo<PostMessagePrinting>(); 
                       var typeCallBack = msgCallBack.Type; //"CheckPrinter"
                       var valueCallBack = msgCallBack.Value; // null
                  }
            }
        }                    

What is problem: Now, I'm using the above code and can not get new message when run dynamic msgCallBack = e.ConvertMessageTo<PostMessagePrinting>(); . Value of variable msgCallBack is not change, it is same as variable msg.
So what I need to do to get new message and send result to web to get real time?

[amaitland]

• Every PostMessage call raises a new instance of the JavascriptMessageReceived event
• Your javascript callback function needs to return a value if you want to populate the JavascriptResponse.Result property.

[phuocminh6464]

@amaitland Thanks you, I did it.