本文不仅适用于图片，同样实用于其它二进制文件。
需要四个类：WebRequest、WebResponse、Stream、FileStream。
WebRequest、WebResponse 的名称空间是：
System.Net
Stream、FileStream 的名称空间是：
System.IO
核心代码
WebRequest request = WebRequest.Create("http://www.cftea.com/images/logo.gif");
WebResponse response = request.GetResponse();
Stream reader = response.GetResponseStream();
FileStream writer = new FileStream("D:\\logo.gif", 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)
{
writer.Write(buff, 0, c);
}
writer.Close();
注意类 Stream，不是 StreamReader。
示例
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Net" %>
<%@ Import Namespace="System.IO" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
void Page_Load(object sender, EventArgs e)
{
try
{
WebRequest request = WebRequest.Create("http://www.cftea.com/images/logo.gif");
WebResponse response = request.GetResponse();
Stream reader = response.GetResponseStream();
FileStream writer = new FileStream("D:\\logo.gif", 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)
{
writer.Write(buff, 0, c);
}
writer.Close();
writer.Dispose();
reader.Close();
reader.Dispose();
response.Close();
tb.Text = "保存成功！";
}
catch (Exception ex)
{
tb.Text = ex.Message;
}
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="tb" runat="server" Width="500" Height="300" TextMode="multiLine"></asp:TextBox>
</div>
</form>
</body>
</html>
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