URLOpenBlockingStream

[DllImport("urlmon.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern int URLOpenBlockingStream(
   IntPtr pCaller,
   [MarshalAs(UnmanagedType.LPWStr)] string szURL,
   out IntPtr ppStream,
   int dwReserved,
   IntPtr lpfnCB
);

Microsoft documentation: Link