cefsharp/CefSharp · error · InvalidOperationException

Method {0} not found on Object of Type {1}

Error message

Method {0} not found on Object of Type {1}

What it means

Thrown by the SYNCHRONOUS TryCallMethod path when the bound object was found (its objectId resolved) but no method on it has a JavascriptName matching the requested name. The earlier 'object not found' case returns a TryCallMethodResult instead of throwing, but a name mismatch here raises InvalidOperationException. method.JavascriptName is the camelCased name exposed to JavaScript.

Source

Thrown at CefSharp/Internals/JavascriptObjectRepository.cs:304

        }

        protected virtual TryCallMethodResult TryCallMethod(long objectId, string name, object[] parameters)
        {
            var exception = "";
            object result = null;
            JavascriptObject obj;

            if (!objects.TryGetValue(objectId, out obj))
            {
                var paramCount = parameters == null ? 0 : parameters.Length;

                return new TryCallMethodResult(false, result, $"Object Not Found Matching Id:{objectId}, MethodName:{name}, ParamCount:{paramCount}");
            }

            var method = obj.Methods.FirstOrDefault(p => p.JavascriptName == name);
            if (method == null)
            {
                throw new InvalidOperationException(string.Format("Method {0} not found on Object of Type {1}", name, obj.Value.GetType()));
            }

            try
            {
                //Check if the bound object method contains a ParamArray as the last parameter on the method signature.
                //NOTE: No additional parameters are permitted after the params keyword in a method declaration,
                //and only one params keyword is permitted in a method declaration.
                //https://msdn.microsoft.com/en-AU/library/w5zay9db.aspx
                if (method.HasParamArray)
                {
                    var paramList = new List<object>(method.Parameters.Count);

                    //Loop through all of the method parameters on the bound object.
                    for (var i = 0; i < method.Parameters.Count; i++)
                    {
                        //If the method parameter is a paramArray IE: (params string[] args)
                        //grab the parameters from the javascript function starting at the current bound object parameter index
                        //and add create an array that will be passed in as the last bound object method parameter.

View on GitHub (pinned to 16bc6e0711)

Solutions

1. Call the method by its JavaScript (camelCase) name, not the C# PascalCase name.
2. Verify the method exists on the bound object and is included by your BindingOptions.
3. Inspect obj.Methods to see the exposed JavascriptName values and match them exactly.
4. Keep C# method names stable or regenerate the TS/JS contract after renames.

Example fix

// C#: public void DoWork()  ->  JS name "doWork"
// before (JS): cefSharp bonded obj.doWorkSync(); // wrong name
// after  (JS): await obj.doWork();

var exposed = obj.Methods.Select(m => m.JavascriptName);
if (!exposed.Contains(jsMethodName, StringComparer.Ordinal))
    throw new InvalidOperationException($"Method {jsMethodName} not exposed. Known: {string.Join(", ", exposed)}");

try { repository.TryCallMethod(...); }
catch (InvalidOperationException ex) when (ex.Message.Contains("Method") && ex.Message.Contains("not found"))
{ /* unknown method name from JS; log and ignore */ }

When it happens

Trigger: JavaScript calls a bound method by a name that does not exist (typo, wrong casing, or a method that was filtered out by binding options); calling a method on the wrong object id; method was renamed on the C# side but JS still uses the old name.

Common situations: Renaming a C# method and forgetting to update JS; relying on the managed name instead of the javascript (camelCase) name; binding options excluding the method; interop name mangling differences.

Related errors

• Could not execute method: {name}({parameters}) {optional: -
• Property {0} not found on Object of Type {1}
• name
• value
• To enable synchronous JS bindings set WcfEnabled true in Cef

AI-assisted analysis of cefsharp/CefSharp@16bc6e0711 (2026-08-13). Data as JSON: /api/errors/bcaea8dfa727342a. Report an issue: GitHub.