Passing a javascript object to c# in jint

Question

I'm trying to send a javascript object to c# world but i cannot figure out how is done.

Here is my javascript code

myClass.Do( 'str', { key : 'Testing' } );

And I have tried to these method signatures on c# class, first parameter is correct but second parameter is always null.

public Do(string param1, object param2); // param1 = 'str', param2 = null
public Do(string param1, dynamic param2); // param1 = 'str', param2 = null
public Do(string param1, JsObject param2); // param1 = 'str', param2 = null
public Do(string param1, JsDictionary param2); // param1 = 'str', param2 = null
public Do(string param1, ArgumentClass param2); // param1 = 'str', param2 = null
public Do(string param1, object[] param2); // throws method not found

Is there any way to do this ?

Answer 1

The JavaScript code you posted doesn’t parse. Could it be that your particular JavaScript interpreter is very lenient and reinterprets the call as myClass.Do('str')? That would explain the nulls.

Answer 2

In .NET 4.0, specify that the second param is dynamic and you should get an object reference you can work with. In 3.5 and below, it'll be a JsObject of some kind, but the entire Microsoft.JScript namespace isn't supposed to be used directly so I'm not too sure if you can specify that you'll be taking a JsObject.

Is "key" supposed to be a string literal or the name of another variable? You're also missing a closing quote on "Testing". I seriously doubt that JS will compile correctly exactly as written.

Answer 3

I had to modify this method in Native\JsClr.cs

public static object ConvertParameter(JsInstance parameter)
{
    if (parameter.Class != JsFunction.TYPEOF && parameter.Class != JsArray.TYPEOF && parameter.Class != JsObject.TYPEOF)
    {
        return parameter.Value;
    }
    else if (parameter == JsNull.Instance)
    {
        return null;
    }
    else
    {
        JsFunction constructor = ((JsDictionaryObject)parameter)["constructor"] as JsFunction;
        if (constructor == null) return parameter;

        switch (constructor.Name)
        {
            case "Date":
                return JsDateConstructor.CreateDateTime(parameter.ToNumber());
            case "String":
            case "RegExp":
            case "Number":
                return parameter.Value;
            case "Array":
                object[] array = new object[((JsObject)parameter).Length];
                foreach (KeyValuePair<string, JsInstance> key in (JsObject)parameter)
                {
                    int index = 0;
                    if (int.TryParse(key.Key, out index))
                    {
                        array[index] = ConvertParameters(key.Value)[0];
                    }
                }
                return array;
            case "Object":

                if (parameter.Class == JsFunction.TYPEOF) return parameter;

                Dictionary<string, object> dic = new Dictionary<string, object>();
                foreach (KeyValuePair<string, JsInstance> key in (JsObject)parameter)
                {
                    dic.Add(key.Key, ConvertParameter(key.Value));
                }
                return dic;
            default:
                return parameter;
        }
    }

}

Here's the function setup:

m_Engine = new JintEngine(Options.Ecmascript3);
m_Engine.SetFunction("Compute", new Jint.Delegates.Func<object, object>(JSCompute));

In the method I cast the parameter to Dictionary to get the values but return a constructed JsObject. If any of the properties are objects themselves, you can cast them as Dictionary also:

public object JSCompute(object o)
{
    Dictionary<string, object> properties = (Dictionary<string, object>)o;
    double x = (int)((double)properties["X"]);
    double y = (int)((double)properties["Y"]);
    double width = (int)((double)properties["Width"]);
    double height = (int)((double)properties["Height"]);

    JsObject results = new JsObject();
    results["Area"] = new JsNumber(width * height);
    results["Diagonal"] = new JsNumber(Math.Sqrt(x * x + y * y));
    return results;
}

Here's the javascript:

var rectangle = { "X": 5, "Y": 10, "Width": 20, "Height": 10 };
var result = Compute(rectangle);
alert('Area is ' + result.Area + ', Diagonal is ' + result.Diagonal);