C# Signature:

[DllImport("wininet.dll", SetLastError=true)]
public static extern bool InternetGetCookie(
  string url, string cookieName, StringBuilder cookieData, ref int size);

VB Signature:

Declare Auto Function InternetGetCookie Lib "wininet.dll" ( _
     ByVal lpszUrlName As String, ByVal lpszCookieName As String, _
     ByVal lpszCookieData As String, ByRef lpdwSize As Integer) As Boolean

User-Defined Types:

None.

Notes:

You can pass null (Nothing in Visual Basic) to the lpszCookieData parameter to get the require buffer size from the lpdwSize parameter.

Tips & Tricks:

Please add some!

Sample Code:

private static CookieContainer GetUriCookieContainer(Uri uri)

{

  CookieContainer cookies = null;

  // Determine the size of the cookie
  int datasize = 256;
  StringBuilder cookieData = new StringBuilder(datasize);

  if (!InternetGetCookie(uri.ToString(), null, cookieData,
    ref datasize))
  {
    if (datasize < 0)
      return null;

    // Allocate stringbuilder large enough to hold the cookie
    cookieData = new StringBuilder(datasize);
    if ( !InternetGetCookie(uri.ToString(), null, cookieData,
      ref datasize) )
      return null;
  }

  if (cookieData.Length > 0)
  {
    cookies = new CookieContainer();
    cookies.SetCookies(uri, cookieData.ToString().Replace(';', ','));
  }
  return cookies;

}

Alternative Managed API:

Do you know one? Please contribute it!