cefsharp/CefSharp · error · ArgumentNullException

value

Error message

value

What it means

Thrown by JavascriptObjectRepository.Register when the value (the .NET object to bind) is null. CefSharp reflects over the object to generate JavaScript-callable proxies; a null target has no methods/properties to bind, so Register rejects it with ArgumentNullException. This check runs before Freeze() and before the system-type validation.

Source

Thrown at CefSharp/Internals/JavascriptObjectRepository.cs:210

            objects[id] = result;

            return result;
        }

#if NETCOREAPP
        public void Register(string name, object value, BindingOptions options)
#else
        public void Register(string name, object value, bool isAsync, BindingOptions options)
#endif
        {
            if (name == null)
            {
                throw new ArgumentNullException("name");
            }

            if (value == null)
            {
                throw new ArgumentNullException("value");
            }

            Freeze();

            //Enable WCF if not already enabled - can only be done before the browser has been initliazed
            //if done after the subprocess won't be WCF enabled it we'll have to throw an exception
#if NETCOREAPP
            var isAsync = true;
#else
            if (!IsBrowserInitialized && !isAsync)
            {
                CefSharpSettings.WcfEnabled = true;
            }

            if (!CefSharpSettings.WcfEnabled && !isAsync)
            {
                throw new InvalidOperationException(@"To enable synchronous JS bindings set WcfEnabled true in CefSharpSettings before you create
                                                    your ChromiumWebBrowser instances.");

View on GitHub (pinned to 16bc6e0711)

Solutions

1. Ensure the object instance is constructed and non-null before calling Register.
2. Validate the value from DI/factory sources and fail loudly or skip if null.
3. Avoid registering types whose base namespace is System.* (a later check rejects built-in types) — wrap them in your own class.

Example fix

// before
repo.Register("myApi", serviceInstance, new BindingOptions());

// after
if (serviceInstance == null) throw new InvalidOperationException("Service not resolved before binding.");
repo.Register("myApi", serviceInstance, new BindingOptions());

if (value == null)
{
    throw new InvalidOperationException("Object to bind is not resolved.");
}
repo.Register(name, value, new BindingOptions());

static bool IsBindable(object value) => value != null;

When it happens

Trigger: Calling Register(name, null, ...) where the object to expose was never instantiated, came from a DI/factory that returned null, or was conditionally created and the condition was false.

Common situations: DI container failing to resolve the bound service; a factory method returning null on misconfiguration; binding in a loop where some entries have no instance yet; lazy initialization that has not run before Register.

Related errors

• name
• Please provide a valid array
• converter
• manager
• Please provide a valid filePath

AI-assisted analysis of cefsharp/CefSharp@16bc6e0711 (2026-08-13). Data as JSON: /api/errors/45101bd635fd938d. Report an issue: GitHub.