Another approach might be to insert the following into the DOM:

Then just execute that function using the document.Script property (defined on IHTMLDocument), which would allow you to capture the return value.

It's a bit of a pain to use though because it only exposes the IDispatch interface so you either have to use reflection to make the appropriate call or use a loosely-typed language (Boo? ;)

Ayende,

Here is a quick example:

Assuming you have already inserted the following into the DOM:

The following code:

Type scriptEngType = ie.HtmlDocument.Script.GetType();

int result = (int)scriptEngType.InvokeMember("myeval", BindingFlags.InvokeMethod, null, ie.HtmlDocument.Script, null);

Console.WriteLine("Result: {0}", result);

...will print out: Result: 77

Hope that helps.

@Stan: Neat trick!

This is what I put into our little WebTestFramework here. It's similar to WatiN.

    /// <summary>

    /// Evaluates the specified JavaScript code within the scope of this

    /// document.  Returns the value computed by the last expression in the

    /// code block after implicit conversion to a string.

    /// </summary>

    /// <example>

    /// The following example shows an alert dialog then returns the string "4".

    /// 

        /// EvaluateJavaScript("window.alert('Hello world!'); 2 + 2");

        /// 

    /// </example>

    /// <param name="javaScriptCode">The JavaScript code</param>

    /// <returns>The result converted to a string</returns>

    /// <exception cref="JavaScriptException">Thrown when the JavaScript code cannot be evaluated

    /// or throws an exception during evaluation</exception>

    public string EvaluateJavaScript(string javaScriptCode)

    {

        const string resultPropertyName = "___expressionResult___";

        const string errorPropertyName = "___expressionError___";


        string exprWithAssignment = "try {\n"

            + "document." + resultPropertyName + "= String(eval('" + javaScriptCode.Replace("'", "\\'") + "'))\n"

            + "} catch (error) {\n"

            + "document." + errorPropertyName + "= 'message' in error ? error.name + ': ' + error.message : String(error)\n"

            + "}";


        string result = null, error = null;


        Browser.Sync(delegate

        {

            // Prepare a property to acquire the result.

            IHTMLDocument2 domDocument = (IHTMLDocument2) DomReference;

            IHTMLWindow2 domWindow = domDocument.parentWindow;

            IExpando domDocumentExpando = (IExpando) domDocument;


            PropertyInfo resultProperty = InitializeExpandoProperty(domDocumentExpando, resultPropertyName);

            PropertyInfo errorProperty = InitializeExpandoProperty(domDocumentExpando, errorPropertyName);


            // Run the script.

            // The result value is not meaningful.

            domWindow.execScript(exprWithAssignment, "JavaScript");


            // Obtain the result and error.

            result = (string)resultProperty.GetValue(domDocument, null);

            error = (string)errorProperty.GetValue(domDocument, null);

        });


        if (error != null)

            throw new JavaScriptException(error);


        return result;

    }


    private static PropertyInfo InitializeExpandoProperty(IExpando expando, string propertyName)

    {

        PropertyInfo propertyInfo = expando.GetProperty(propertyName, BindingFlags.Instance);

        if (propertyInfo == null)

            propertyInfo = expando.AddProperty(propertyName);


        propertyInfo.SetValue(expando, null, null);

        return propertyInfo;

    }