Handle windows authentication pop up on Chrome

First of all you don’t need AutoIt, you can just use the windows API. Secondly, Chrome’s basic authentication dialog is not a traditional Window, so you can’t get a handle to it (Try using Spy++). The only reason this would work is if you didn’t bring another window to the foreground prior to the SendKeys call. You need to find the parent Chrome window, which may be something like “URL – Google Chrome”, move it to the front and then send keys. Here’s an example:

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

[DllImport("User32.dll")]
private static extern bool SetForegroundWindow(IntPtr point);

[DllImport("user32.dll")]
private static extern IntPtr FindWindow(string className, string windowTitle);

public static void SendBasicAuthentication(string username, string password, string windowTitle)
{
    var hwnd = FindWindow(null, windowTitle);
    if (hwnd.ToInt32() <= 0 || !SetForegroundWindow(hwnd)) return;
    SendKeys.SendWait(username.EscapeStringForSendKeys());
    SendKeys.SendWait("{TAB}");
    SendKeys.SendWait(password.EscapeStringForSendKeys());
    SendKeys.SendWait("{ENTER}");
}

static string EscapeStringForSendKeys(this string input)
{
    // https://msdn.microsoft.com/en-us/library/system.windows.forms.sendkeys.aspx
    // must do braces first
    return input.Replace("{", "{{}")
        .Replace("}", "{}}")
        .Replace("^", "{^}")
        .Replace("%", "{%}")
        .Replace("~", "{~}")
        .Replace("(", "{(}")
        .Replace(")", "{)}")
        .Replace("[", "{[}")
        .Replace("]", "{]}");
}

Hope that helps.