How to handle File download dialog/popup in IE browser USING SELENIUM and C#

 AutoItX3 autoit = new AutoItX3();                autoit.WinActivate("Save");                            Thread.Sleep(1000);                autoit.Send("{F6}");                Thread.Sleep(1000);                autoit.Send("{TAB}");                Thread.Sleep(1000);                autoit.Send("{ENTER}");

You can try this code.

using System;using Microsoft.VisualStudio.TestTools.UnitTesting;using OpenQA.Selenium;using OpenQA.Selenium.IE;    using OpenQA.Selenium.Support.UI;using System.Threading;using System.Collections.Generic;using System.Windows.Forms;//using NUnit.Framework;namespace SampleTest{    [TestMethod]    public void Download()    {        IWebDriver driver = new InternetExplorerDriver(@"C:\Users\hamit\Desktop\Selenium\IEDriverServer_Win32_2.48.0");        driver.Navigate().GoToUrl("https://www.spotify.com/se/download/windows/");        Thread.Sleep(2000);        SendKeys.SendWait("@{TAB}"); Thread.Sleep(100);        SendKeys.SendWait("@{TAB}"); Thread.Sleep(100);        SendKeys.SendWait("@{DOWN}"); Thread.Sleep(100);        SendKeys.SendWait("@{DOWN}"); Thread.Sleep(100);        SendKeys.SendWait("@{Enter}");    }}

like an option - try get all exist buttons and then filter by inner text

var posibleButtons = driver.FindElements(By.TagName("button")).Where(el => el.Text.Contains("Open"));posibleButtons.Where(// try use some other filters, maybe by styles or ets...