Why this code using InternetSetCookie to set cookies at a WebBroser control is not working?

Question

I've done this sample to try to understand why I'm not sending cookies at all with my WebBrowser, it's pretty simple, the form has a WebBrowser on it, that's all:

namespace BrowserTest
{
    public partial class Form1 : Form
    {
        [DllImport("wininet.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern bool InternetSetCookie(string url, string name, string data);

        public static bool SetWinINETCookieString(string url, string name, string data)
        {
            return Form1.InternetSetCookie(url, name, data);
        }

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // None of two works
            //SetWinINETCookieString("www.nonexistent.com", null, "dataToTest=thisIsTheData");
            SetWinINETCookieString("www.nonexistent.com", "dataToTest", "thisIsTheData");
            this.webBrowser1.Navigate("www.nonexistent.com");
        }
    }
}

And that's what Fidller says I'm sending:

Looks like everyone using this function succeeds but for the life of me that I cannot get it working. I've tried at different computers and it fails there too. Any help will be great, thanks.

Answer 1

Just came across this myself.For completeness, you need to check the value returned from InternetSetCookie and if false, call GetLastError which would have given you a return code of 87 - invalid parameter.

i.e.

[DllImport("kernel32.dll")]
public static extern uint GetLastError();

......

bool ok = SetWinINETCookieString("www.nonexistent.com", "dataToTest", "thisIsTheData");
if (!ok)
{
  int errorCode = GetLastError(); //this will return 87  for www.nonexistent.com
}