HttpWebRequest webRequest = (HttpWebRequest)System.Net.WebRequest.Create(url);
                    webRequest.Credentials = System.Net.CredentialCache.DefaultCredentials;
                    webRequest.Accept = "text/xml";
                    webRequest.AllowAutoRedirect = true;
                    HttpWebResponse webResponse=null;
                    Stream s = null;
                    try
                    {
                        webResponse = (HttpWebResponse)webRequest.GetResponse();
                        s = webResponse.GetResponseStream();
                    }
                    catch
                    {
                        
                    }

Configuration config = ConfigurationManager.OpenExeConfiguration(
  ConfigurationUserLevel.None);
SettingsSection section = (SettingsSection)config.GetSection(
  "system.net/settings");
section.HttpWebRequest.UseUnsafeHeaderParsing = false;
config.Save();

public static bool SetAllowUnsafeHeaderParsing()
{
  //Get the assembly that contains the internal class
  Assembly aNetAssembly = Assembly.GetAssembly(
    typeof(System.Net.Configuration.SettingsSection));
  if (aNetAssembly != null)
  {
    //Use the assembly in order to get the internal type for 
    // the internal class
    Type aSettingsType = aNetAssembly.GetType(
      "System.Net.Configuration.SettingsSectionInternal");
    if (aSettingsType != null)
    {
      //Use the internal static property to get an instance 
      // of the internal settings class. If the static instance 
      // isn't created allready the property will create it for us.
      object anInstance = aSettingsType.InvokeMember("Section",
        BindingFlags.Static | BindingFlags.GetProperty 
        | BindingFlags.NonPublic, null, null, new object[] { });
      if (anInstance != null)
      {
        //Locate the private bool field that tells the 
        // framework is unsafe header parsing should be 
        // allowed or not
        FieldInfo aUseUnsafeHeaderParsing = aSettingsType.GetField(
          "useUnsafeHeaderParsing", 
          BindingFlags.NonPublic | BindingFlags.Instance);
        if (aUseUnsafeHeaderParsing != null)
        {
          aUseUnsafeHeaderParsing.SetValue(anInstance, true);
          return true;
        }
      }
    }
  }
  return false;
}