WebClient 三
WebClient(1,2)中只要介绍了关于通过方法OpenRead 和OpenReadAsync 获取数据流，读取Url资源数据流外，WebClient还包括其他方法读取资源
如：DownloadData 和DowloadDataAsync 读取数据流，单核心本质上和openRead没有任何区别，起始还是通过webRequest 和webResponse 获取数据流,
DownloadDate 只是把数量流转换成byte [] 数据，DownloadString 和DownloadStringAsync 起始就是对DownLoadData 直接调用方法。
具体实现和代码做如下：
WebClient webclient = new WebClient();
byte[] byteData = webclient.DownloadData("http://www.cnblogs.com/");
string result = System.Text.Encoding.UTF8.GetString(byteData);
AppLog.Write(result, AppLog.LogMessageType.Info);
//异步调用
webclient.DownloadDataCompleted += new DownloadDataCompletedEventHandler(DownDataCallback);
webclient.DownloadDataAsync(new Uri("http://www.cnblogs.com/"));
public static void DownDataCallback(Object sender, DownloadDataCompletedEventArgs e)
{
byte[] reply;
reply = (byte[])e.Result;
string strResult = System.Text.Encoding.UTF8.GetString(reply);
AppLog.Write(strResult, AppLog.LogMessageType.Info);
}
Webclient DowloadData 中具体是通过通过webRequest 和webResponse 读取指定url数据流，其中本质上和OpenRead() 基本相同，
主要的区别是DownloadData读取数据流抓换成二进制数据byte[]，具体实现原代码是怎样呢，以下是DownloadData 的核心代码如下：
1 WebRequest request = WebRequest.Create("address") ;
3 Stream stream = response.GetResponseStream();
4 int length = (int)response.ContentLength;
5 MemoryStream ms = null;
6 bool nolength = (length == -1);
7 int size = ((nolength) ? 8192 : length);
8 if (nolength)
9 ms = new MemoryStream();
10 ;
11 int nread = 0;
12 int offset = 0;
13 byte[] buffer = new byte[size];
14 while ((nread = stream.Read(buffer, offset, size)) != 0)
15 {
16 if (nolength)
17 {
18 ms.Write(buffer, 0, nread);
19 }
20 else
21 {
22 offset += nread;
23 size -= nread;
24 }
25 if (async) //异步读取数据
26 {
27 OnDownloadProgressChanged(new DownloadProgressChangedEventArgs(nread, length, userToken));
28 }
29 }
和DownloadData 类型DownloadString 功能类型，后者组要是调用前者实现其功能的，看如下DownloaString 代码如下：
1 WebClient webclient = new WebClient();
3 AppLog.Write(result, AppLog.LogMessageType.Error);
4
5
6 //异步调用
7 webclient.DownloadDataCompleted += new DownloadDataCompletedEventHandler(DownDataCallback);
8 webclient.DownloadDataAsync(new Uri("http://www.cnblogs.com/"));
9
10
11
12 public static void DownloadStringCallBack(object sender, DownloadStringCompletedEventArgs e)
13 {
14 string result = e.Result.ToString();
15 AppLog.Write(result, AppLog.LogMessageType.Error);
16 }
除了实现方法相似外，DownloadString 代码是通过调用方法是通过 encoding.GetString (DownloadData (CreateUri (address))) ，把括DownloadStringAsyn 异步方法也是调用DownloadData 实现其功能。另外还有方法DownloadFile 和 DownloadFileAsync 是制定url 资源下载数据，也是读取数据流，然后保存在本地文件而已，具体功能更
和势力代码如下：由于功能类型，在这里就不再多做解释，把实例代码贴出来供大家参考。
1
3 webclient.DownloadFile("http://www.cnblogs.com/", fileName);
4
5 //异步调用
6 webclient.DownloadFileCompleted += new System.ComponentModel.AsyncCompletedEventHandler(DownloadFileCompletedCallback);
7 webclient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgressCallback);
8 webclient.DownloadFileAsync(new Uri("http://www.cnblogs.com/"), fileName)
9
10 static void DownloadProgressCallback(object sender, DownloadProgressChangedEventArgs e)
11 {
12
13 string progress = string.Format("{0} downloaded {1} of {2} bytes. {3} % complete...",
14 (string)e.UserState,e.BytesReceived,e.TotalBytesToReceive, e.ProgressPercentage);
15 AppLog.Write(progress, AppLog.LogMessageType.Error);
16 }
以上是读取去资源数据信息到本地，如果想上传到指定url指定资源信息。也是类似。未完待续 。。。。。
