将HTTP身份验证与C#WebRequest一起使用

我想向需要身份验证的页面发出Web请求.我该怎么做呢？我找到了一些可能使用Credentials属性的内容,但我不确定如何使用它.

NetworkCredential为Credentials属性分配新实例:

webClient.Credentials = new NetworkCredential("Mehrdad", "Password");

基本身份验证示例:

public void SetBasicAuthHeader(WebRequest req, String userName, String userPassword)
{
    string authInfo = userName + ":" + userPassword;
    authInfo = Convert.ToBase64String(Encoding.Default.GetBytes(authInfo));
    req.Headers["Authorization"] = "Basic " + authInfo;
}

http://blog.kowalczyk.info/article/at3/Forcing-basic-http-authentication-for-HttpWebReq.html