对HttpWebRequest/HttpWebResponse 进行封装处理，提供方便的接口向互联网发送或接收数据。支持POST urlencode形式的字符串以及mulitpart/form-data形式的二进制或文本数据，支持GET方式获取数据。自动管理Cookie，解 决网络访问中难以处理的权限问题。支持gzip,deflate编码数据解压。测试代码见代码后面。

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Data; 
using System.IO; 
using System.Net; 
using System.Net.Security; 
using System.Security.Cryptography.X509Certificates; 
using System.IO.Compression; 
using System.Net.Cache; 

namespace HttpProc 
{ 
    /// <summary> 
    /// 上传数据参数 
    /// </summary> 
    public class UploadEventArgs : EventArgs 
    { 
        int bytesSent; 
        int totalBytes; 
        /// <summary> 
        /// 已发送的字节数 
        /// </summary> 
        public int BytesSent 
        { 
            get { return bytesSent; } 
            set { bytesSent = value; } 
        } 
        /// <summary> 
        /// 总字节数 
        /// </summary> 
        public int TotalBytes 
        { 
            get { return totalBytes; } 
            set { totalBytes = value; } 
        } 
    } 
    /// <summary> 
    /// 下载数据参数 
    /// </summary> 
    public class DownloadEventArgs : EventArgs 
    { 
        int bytesReceived; 
        int totalBytes; 
        byte[] receivedData; 
        /// <summary> 
        /// 已接收的字节数 
        /// </summary> 
        public int BytesReceived 
        { 
            get { return bytesReceived; } 
            set { bytesReceived = value; } 
        } 
        /// <summary> 
        /// 总字节数 
        /// </summary> 
        public int TotalBytes 
        { 
            get { return totalBytes; } 
            set { totalBytes = value; } 
        } 
        /// <summary> 
        /// 当前缓冲区接收的数据 
        /// </summary> 
        public byte[] ReceivedData 
        { 
            get { return receivedData; } 
            set { receivedData = value; } 
        } 
    } 

    public class WebClient 
    { 
        Encoding encoding = Encoding.Default; 
        string respHtml = ""; 
        WebProxy proxy; 
        static CookieContainer cc; 
        WebHeaderCollection requestHeaders; 
        WebHeaderCollection responseHeaders; 
        int bufferSize = 15240; 
        public event EventHandler<UploadEventArgs> UploadProgressChanged; 
        public event EventHandler<DownloadEventArgs> DownloadProgressChanged; 
        static WebClient() 
        { 
            LoadCookiesFromDisk(); 
        } 
        /// <summary> 
        /// 创建WebClient的实例 
        /// </summary> 
        public WebClient() 
        { 
            requestHeaders = new WebHeaderCollection(); 
            responseHeaders = new WebHeaderCollection(); 
        } 
        /// <summary> 
        /// 设置发送和接收的数据缓冲大小 
        /// </summary> 
        public int BufferSize 
        { 
            get { return bufferSize; } 
            set { bufferSize = value; } 
        } 
        /// <summary> 
        /// 获取响应头集合 
        /// </summary> 
        public WebHeaderCollection ResponseHeaders 
        { 
            get { return responseHeaders; } 
        } 
        /// <summary> 
        /// 获取请求头集合 
        /// </summary> 
        public WebHeaderCollection RequestHeaders 
        { 
            get { return requestHeaders; } 
        } 
        /// <summary> 
        /// 获取或设置代理 
        /// </summary> 
        public WebProxy Proxy 
        { 
            get { return proxy; } 
            set { proxy = value; } 
        } 
        /// <summary> 
        /// 获取或设置请求与响应的文本编码方式 
        /// </summary> 
        public Encoding Encoding 
        { 
            get { return encoding; } 
            set { encoding = value; } 
        } 
        /// <summary> 
        /// 获取或设置响应的html代码 
        /// </summary> 
        public string RespHtml 
        { 
            get { return respHtml; } 
            set { respHtml = value; } 
        } 
        /// <summary> 
        /// 获取或设置与请求关联的Cookie容器 
        /// </summary> 
        public CookieContainer CookieContainer 
        { 
            get { return cc; } 
            set { cc = value; } 
        } 
        /// <summary> 
        ///  获取网页源代码 
        /// </summary> 
        /// <param name="url">网址</param> 
        /// <returns></returns> 
        public string GetHtml(string url) 
        { 
            HttpWebRequest request = CreateRequest(url, "GET"); 
            respHtml = encoding.GetString(GetData(request)); 
            return respHtml; 
        } 
        /// <summary> 
        /// 下载文件 
        /// </summary> 
        /// <param name="url">文件URL地址</param> 
        /// <param name="filename">文件保存完整路径</param> 
        public void DownloadFile(string url, string filename) 
        { 
            FileStream fs = null; 
            try 
            { 
                HttpWebRequest request = CreateRequest(url, "GET"); 
                byte[] data = GetData(request); 
                fs = new FileStream(filename, FileMode.Create, FileAccess.Write); 
                fs.Write(data, 0, data.Length); 
            } 
            finally 
            { 
                if (fs != null) fs.Close(); 
            } 
        } 
        /// <summary> 
        /// 从指定URL下载数据 
        /// </summary> 
        /// <param name="url">网址</param> 
        /// <returns></returns> 
        public byte[] GetData(string url) 
        { 
            HttpWebRequest request = CreateRequest(url, "GET"); 
            return GetData(request); 
        } 
        /// <summary> 
        /// 向指定URL发送文本数据 
        /// </summary> 
        /// <param name="url">网址</param> 
        /// <param name="postData">urlencode编码的文本数据</param> 
        /// <returns></returns> 
        public string Post(string url, string postData) 
        { 
            byte[] data = encoding.GetBytes(postData); 
            return Post(url, data); 
        } 
        /// <summary> 
        /// 向指定URL发送字节数据 
        /// </summary> 
        /// <param name="url">网址</param> 
        /// <param name="postData">发送的字节数组</param> 
        /// <returns></returns> 
        public string Post(string url, byte[] postData) 
        { 
            HttpWebRequest request = CreateRequest(url, "POST"); 
            request.ContentType = "application/x-www-form-urlencoded"; 
            request.ContentLength = postData.Length; 
            request.KeepAlive = true; 
            PostData(request, postData); 
            respHtml = encoding.GetString(GetData(request)); 
            return respHtml; 
        } 
        /// <summary> 
        /// 向指定网址发送mulitpart编码的数据 
        /// </summary> 
        /// <param name="url">网址</param> 
        /// <param name="mulitpartForm">mulitpart form data</param> 
        /// <returns></returns> 
        public string Post(string url, MultipartForm mulitpartForm) 
        { 
            HttpWebRequest request = CreateRequest(url, "POST"); 
            request.ContentType = mulitpartForm.ContentType; 
            request.ContentLength = mulitpartForm.FormData.Length; 
            request.KeepAlive = true; 
            PostData(request, mulitpartForm.FormData); 
            respHtml = encoding.GetString(GetData(request)); 
            return respHtml; 
        } 
        /// <summary> 
        /// 读取请求返回的数据 
        /// </summary> 
        /// <param name="request">请求对象</param> 
        /// <returns></returns> 
        private byte[] GetData(HttpWebRequest request) 
        { 
            HttpWebResponse response = (HttpWebResponse)request.GetResponse(); 
            Stream stream = response.GetResponseStream(); 
            responseHeaders = response.Headers; 
            SaveCookiesToDisk(); 

            DownloadEventArgs args = new DownloadEventArgs(); 
            if (responseHeaders[HttpResponseHeader.ContentLength] != null) 
                args.TotalBytes = Convert.ToInt32(responseHeaders[HttpResponseHeader.ContentLength]); 

            MemoryStream ms = new MemoryStream(); 
            int count = 0; 
            byte[] buf = new byte[bufferSize]; 
            while ((count = stream.Read(buf, 0, buf.Length)) > 0) 
            { 
                ms.Write(buf, 0, count); 
                if (this.DownloadProgressChanged != null) 
                { 
                    args.BytesReceived += count; 
                    args.ReceivedData = new byte[count]; 
                    Array.Copy(buf, args.ReceivedData, count); 
                    this.DownloadProgressChanged(this, args); 
                } 
            } 
            stream.Close(); 
            //解压 
            if (ResponseHeaders[HttpResponseHeader.ContentEncoding] != null) 
            { 
                MemoryStream msTemp = new MemoryStream(); 
                count = 0; 
                buf = new byte[100]; 
                switch (ResponseHeaders[HttpResponseHeader.ContentEncoding].ToLower()) 
                { 
                    case "gzip": 
                        GZipStream gzip = new GZipStream(ms, CompressionMode.Decompress); 
                        while ((count = gzip.Read(buf, 0, buf.Length)) > 0) 
                        { 
                            msTemp.Write(buf, 0, count); 
                        } 
                        return msTemp.ToArray(); 
                    case "deflate": 
                        DeflateStream deflate = new DeflateStream(ms, CompressionMode.Decompress); 
                        while ((count = deflate.Read(buf, 0, buf.Length)) > 0) 
                        { 
                            msTemp.Write(buf, 0, count); 
                        } 
                        return msTemp.ToArray(); 
                    default: 
                        break; 
                } 
            } 
            return ms.ToArray(); 
        } 
        /// <summary> 
        /// 发送请求数据 
        /// </summary> 
        /// <param name="request">请求对象</param> 
        /// <param name="postData">请求发送的字节数组</param> 
        private void PostData(HttpWebRequest request, byte[] postData) 
        { 
            int offset = 0; 
            int sendBufferSize = bufferSize; 
            int remainBytes = 0; 
            Stream stream = request.GetRequestStream(); 
            UploadEventArgs args = new UploadEventArgs(); 
            args.TotalBytes = postData.Length; 
            while ((remainBytes = postData.Length - offset) > 0) 
            { 
                if (sendBufferSize > remainBytes) sendBufferSize = remainBytes; 
                stream.Write(postData, offset, sendBufferSize); 
                offset += sendBufferSize; 
                if (this.UploadProgressChanged != null) 
                { 
                    args.BytesSent = offset; 
                    this.UploadProgressChanged(this, args); 
                } 
            } 
            stream.Close(); 
        } 
        /// <summary> 
        /// 创建HTTP请求 
        /// </summary> 
        /// <param name="url">URL地址</param> 
        /// <returns></returns> 
        private HttpWebRequest CreateRequest(string url, string method) 
        { 
            Uri uri = new Uri(url); 

            if (uri.Scheme == "https") 
                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(this.CheckValidationResult); 

            // Set a default policy level for the "http:" and "https" schemes. 
            HttpRequestCachePolicy policy = new HttpRequestCachePolicy(HttpRequestCacheLevel.Revalidate); 
            HttpWebRequest.DefaultCachePolicy = policy; 

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri); 
            request.AllowAutoRedirect = false; 
            request.AllowWriteStreamBuffering = false; 
            request.Method = method; 
            if (proxy != null) request.Proxy = proxy; 
            request.CookieContainer = cc; 
            foreach (string key in requestHeaders.Keys) 
            { 
                request.Headers.Add(key, requestHeaders[key]); 
            } 
            requestHeaders.Clear(); 
            return request; 
        } 
        private bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors) 
        { 
            return true; 
        } 
        /// <summary> 
        /// 将Cookie保存到磁盘 
        /// </summary> 
        private static void SaveCookiesToDisk() 
        { 
            string cookieFile = System.Environment.GetFolderPath(Environment.SpecialFolder.Cookies) + "\\webclient.cookie"; 
            FileStream fs = null; 
            try 
            { 
                fs = new FileStream(cookieFile, FileMode.Create); 
                System.Runtime.Serialization.Formatters.Binary.BinaryFormatter formater = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter(); 
                formater.Serialize(fs, cc); 
            } 
            finally 
            { 
                if (fs != null) fs.Close(); 
            } 
        } 
        /// <summary> 
        /// 从磁盘加载Cookie 
        /// </summary> 
        private static void LoadCookiesFromDisk() 
        { 
            cc = new CookieContainer(); 
            string cookieFile = System.Environment.GetFolderPath(Environment.SpecialFolder.Cookies) + "\\webclient.cookie"; 
            if (!File.Exists(cookieFile)) 
                return; 
            FileStream fs = null; 
            try 
            { 
                fs = new FileStream(cookieFile, FileMode.Open, FileAccess.Read, FileShare.Read); 
                System.Runtime.Serialization.Formatters.Binary.BinaryFormatter formater = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter(); 
                cc = (CookieContainer)formater.Deserialize(fs); 
            } 
            finally 
            { 
                if (fs != null) fs.Close(); 
            } 
        } 
    } 





    /// <summary> 
    /// 对文件和文本数据进行Multipart形式的编码 
    /// </summary> 
    public class MultipartForm 
    { 
        private Encoding encoding; 
        private MemoryStream ms; 
        private string boundary; 
        private byte[] formData; 
        /// <summary> 
        /// 获取编码后的字节数组 
        /// </summary> 
        public byte[] FormData 
        { 
            get 
            { 
                if (formData == null) 
                { 
                    byte[] buffer = encoding.GetBytes("--" + this.boundary + "--\r\n"); 
                    ms.Write(buffer, 0, buffer.Length); 
                    formData = ms.ToArray(); 
                } 
                return formData; 
            } 
        } 
        /// <summary> 
        /// 获取此编码内容的类型 
        /// </summary> 
        public string ContentType 
        { 
            get { return string.Format("multipart/form-data; boundary={0}", this.boundary); } 
        } 
        /// <summary> 
        /// 获取或设置对字符串采用的编码类型 
        /// </summary> 
        public Encoding StringEncoding 
        { 
            set { encoding = value; } 
            get { return encoding; } 
        } 
        /// <summary> 
        /// 实例化 
        /// </summary> 
        public MultipartForm() 
        { 
            boundary = string.Format("--{0}--", Guid.NewGuid()); 
            ms = new MemoryStream(); 
            encoding = Encoding.Default; 
        } 
        /// <summary> 
        /// 添加一个文件 
        /// </summary> 
        /// <param name="name">文件域名称</param> 
        /// <param name="filename">文件的完整路径</param> 
        public void AddFlie(string name, string filename) 
        { 
            if (!File.Exists(filename)) 
                throw new FileNotFoundException("尝试添加不存在的文件。", filename); 
            FileStream fs = null; 
            byte[] fileData ={ }; 
            try 
            { 
                fs = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read); 
                fileData = new byte[fs.Length]; 
                fs.Read(fileData, 0, fileData.Length); 
                this.AddFlie(name, Path.GetFileName(filename), fileData, fileData.Length); 
            } 
            catch (Exception) 
            { 
                throw; 
            } 
            finally 
            { 
                if (fs != null) fs.Close(); 
            } 
        } 
        /// <summary> 
        /// 添加一个文件 
        /// </summary> 
        /// <param name="name">文件域名称</param> 
        /// <param name="filename">文件名</param> 
        /// <param name="fileData">文件二进制数据</param> 
        /// <param name="dataLength">二进制数据大小</param> 
        public void AddFlie(string name, string filename, byte[] fileData, int dataLength) 
        { 
            if (dataLength <= 0 || dataLength > fileData.Length) 
            { 
                dataLength = fileData.Length; 
            } 
            StringBuilder sb = new StringBuilder(); 
            sb.AppendFormat("--{0}\r\n", this.boundary); 
            sb.AppendFormat("Content-Disposition: form-data; name=\"{0}\";filename=\"{1}\"\r\n", name, filename); 
            sb.AppendFormat("Content-Type: {0}\r\n", this.GetContentType(filename)); 
            sb.Append("\r\n"); 
            byte[] buf = encoding.GetBytes(sb.ToString()); 
            ms.Write(buf, 0, buf.Length); 
            ms.Write(fileData, 0, dataLength); 
            byte[] crlf = encoding.GetBytes("\r\n"); 
            ms.Write(crlf, 0, crlf.Length); 
        } 
        /// <summary> 
        /// 添加字符串 
        /// </summary> 
        /// <param name="name">文本域名称</param> 
        /// <param name="value">文本值</param> 
        public void AddString(string name, string value) 
        { 
            StringBuilder sb = new StringBuilder(); 
            sb.AppendFormat("--{0}\r\n", this.boundary); 
            sb.AppendFormat("Content-Disposition: form-data; name=\"{0}\"\r\n", name); 
            sb.Append("\r\n"); 
            sb.AppendFormat("{0}\r\n", value); 
            byte[] buf = encoding.GetBytes(sb.ToString()); 
            ms.Write(buf, 0, buf.Length); 
        } 
        /// <summary> 
        /// 从注册表获取文件类型 
        /// </summary> 
        /// <param name="filename">包含扩展名的文件名</param> 
        /// <returns>如：application/stream</returns> 
        private string GetContentType(string filename) 
        { 
            Microsoft.Win32.RegistryKey fileExtKey = null; ; 
            string contentType = "application/stream"; 
            try 
            { 
                fileExtKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(Path.GetExtension(filename)); 
                contentType = fileExtKey.GetValue("Content Type", contentType).ToString(); 
            } 
            finally 
            { 
                if (fileExtKey != null) fileExtKey.Close(); 
            } 
            return contentType; 
        } 
    } 
}

使用实例：

class Test 
    { 
        public static void Test1() 
        { 
            HttpProc.WebClient c = new HttpProc.WebClient(); 
            c.DownloadProgressChanged += new EventHandler<HttpProc.DownloadEventArgs>(c_DownloadProgressChanged); 
            c.UploadProgressChanged += new EventHandler<HttpProc.UploadEventArgs>(c_UploadProgressChanged); 

            //登录百度空间 
            c.Post("https://passport.baidu.com/?login", "username=hddo&password=**********"); 
            if (c.RespHtml.Contains("passport.baidu.com")) 
            { 
                //登录成功 
            } 

            //向百度相册上传图片 
            HttpProc.MultipartForm mf = new HttpProc.MultipartForm(); 
            mf.AddString("BrowserType", "1"); 
            mf.AddString("spPhotoText0", "10086"); 
            mf.AddString("spAlbumName", "默认相册"); 
            mf.AddString("spMaxSize", "1600"); 
            mf.AddString("spQuality", "90"); 
            mf.AddFlie("file1", "D:\\Blue hills2.jpg"); 
            c.Post("http://hiup.baidu.com/hddo/upload", mf); 
            if (c.RespHtml.Contains("submit(0,0)")) 
            { 
                //上传图片成功 
            } 

        } 

        static void c_UploadProgressChanged(object sender, HttpProc.UploadEventArgs e) 
        { 
            //显示上传进度 
        } 

        static void c_DownloadProgressChanged(object sender, HttpProc.DownloadEventArgs e) 
        { 
            //显示下载进度 
        } 

    }

转自:http://hi.baidu.com/¾ÓÖÛ/blog/item/48ef8a76b2b09a13b151b96a.html