How to call methods with Type arguments?

[handerss-spotfire]

If I try call a method which takes a Type as its first argument I get the following error:

Error: The best overloaded method match for 'ClearScriptPlaygroud.ScriptObject.DoSomethingWithType(System.Type)' has some invalid arguments

I guess this happens since ClearScript thinks I'm trying to call a generic method. What is the way to call these types of methods?

Repro:

namespace ClearScriptPlaygroud;

public class ScriptObject
{
    public void DoSomethingWithType(Type aType) { }
}

internal class Program
{
    static void Main(string[] args)
    {
        using var engine = new V8ScriptEngine();

        engine.AddHostObject("host", new HostFunctions());
        var typeCollection = new HostTypeCollection("mscorlib");
        engine.Script["System"] = typeCollection.GetNamespaceNode("System");
        var obj = new ScriptObject();
        engine.AddHostObject("obj", obj);

        engine.Execute(@"obj.DoSomethingWithType(System.String.Type);");
    }
}

[ClearScriptLib]

Hi @handerss-tibco,

I guess this happens since ClearScript thinks I'm trying to call a generic method.

Not quite. Consider this line in your code:

engine.Execute(@"obj.DoSomethingWithType(System.String.Type);");

.NET's String class has no static property named "Type", so the JavaScript expression System.String.Type evaluates to undefined, which isn't a valid argument for DoSomethingWithType.

What is the way to call these types of methods?

In the JavaScript environment, System.String is a host type; it isn't a Type object. A host type is a special object that enables C#-like syntax and capabilities.

Suppose you wanted to call DoSomethingWithType in C#. The following wouldn't work:

obj.DoSomethingWithType(string);

Instead, you'd use the typeof operator to obtain a Type object:

obj.DoSomethingWithType(typeof(string));

In JavaScript, you can use ClearScript's typeOf method to do the same thing:

engine.AllowReflection = true;
engine.Execute(@"obj.DoSomethingWithType(host.typeOf(System.String));");

Good luck!

[handerss-spotfire]

Thanks for the answer! Forgot to remove the ".Type" part when copy-pasting code, nonetheless you answered my question.

typeOf unfortunately requires AllowReflection which may be problematic in our use case.

[ClearScriptLib]

typeOf unfortunately requires AllowReflection which may be problematic in our use case.

Ah. In that case, you could expose the required Type objects directly, provide an alternative for GetType, etc.

Cheers!