Webdriver Firefoxdriver Selenium download file

Question

I am automating the download of a file .xlsx of a website with Selenium with the FirefoxDriver but I can’t interact in the download pop-up of the site!

There’s how I interact with the pop-up by checking Save file and upload to a folder?

I’m using the following code to interfere with the pop-up:

IWebDriver driver = new FirefoxDriver();
            driver.Url = "";

            driver.Manage().Window.Maximize();
            driver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(30);
           driver.FindElement(By.XPath("//button[@class='jss174']")).Click();

            Thread.Sleep(6000);

            driver.FindElement(By.XPath("//input[@class='jss314']")).Click();

            Thread.Sleep(6000);

            driver.FindElement(By.XPath("//img[@src='a95fbd8f692090fb308a787688c0373f.png']")).Click();

            FirefoxProfile profile = new FirefoxProfile();

            profile.AcceptUntrustedCertificates = true;           

            profile.SetPreference("browser.download.folderList", 2);

            profile.SetPreference("browser.download.dir", "c:\\mydownloads");

            //profile.SetPreference("network.http.phishy-userpass-length", 255);
            profile.SetPreference("browser.download.manager.showWhenStarting", false);

            profile.SetPreference("browser.helperApps.neverAsk.saveToDisk", "application/excel");

And I’m getting the following mistake: