从网络下载图片文件到本地

本想自己写程序，将网络上大量的图片下载到本地，那么就得先得到网络上的图片地址，
每个网页，可能都有一些图片，为了下载 整个页面的图片，
需要先下载整个网页，从网页中，找到图片地址。
下载网页一般使用以下两种方法：

1：使用：System.Net.WebClient

    public static void DownloadFile(string sourceUri, string filePath)
    {
        WebClient client = new WebClient();

        string path = "C:\\wendang\\";
        try
        {

            client.DownloadFile(sourceUri, path + filePath);
        }
        catch (Exception ex)
        {
            return;
        }


    }

2:使用:System.Net.HttpWebRequest

using System.Net;
using System.IO;
using System.Windows.Forms;

public void GetFile()
{
	string result = null;
	string url = "http://www.cnblogs.com";
	WebResponse response = null;
	StreamReader reader = null;

	try
	{
	    HttpWebRequest request = (HttpWebRequest)WebRequest.Create( url );
	    request.Method = "GET";
	    response = request.GetResponse();
	    reader = new StreamReader( response.GetResponseStream(), Encoding.UTF8 );
	    result = reader.ReadToEnd();
	}
	catch (Exception ex)
	{
	    return;
	}
	finally
	{
	    if (reader != null)
	        reader.Close();
	    if (response != null)
	        response.Close();
	}
}

找到网页内容，从中找到图片地址，将图片下载到本地

下载图片实际案例

1:WebRequest和WebResponse

	public static void GetFile()
    {
        string url = "http://images.cnblogs.com/logo_small.gif";
        WebResponse response = null;
        Stream reader = null;

        try
        {
            WebRequest request = WebRequest.Create(url);
            request.Method = "GET";
            response = request.GetResponse();
            reader = response.GetResponseStream();
            FileStream write = new FileStream("E:\\pic.jpg", FileMode.OpenOrCreate, FileAccess.Write);
            byte[] buff = new byte[512];
            int c = 0;//实际读取的字节数
            while ((c = reader.Read(buff, 0, buff.Length)) > 0)
            {
                write.Write(buff, 0, c);
            }
            write.Close();
            write.Dispose();
            reader.Close();
            reader.Dispose();
            response.Close();
        }
        catch (Exception ex)
        {
            return;
        }
    }

2：WebClient

    public static void GetFileByWebClient()
    {
        try
        {
            string url = "http://images.cnblogs.com/logo_small.gif";
            string filepath = "E:\\picg.jpg";
            WebClient mywebclient = new WebClient();
            mywebclient.DownloadFile(url, filepath);
        }
        catch (Exception)
        {
            return;
        }
    }