C#实现在winfrom程序中下载文件

//下载文件
//downlaodUrl  系统路径如：http://xxx.xxx.xxx/UpFile/kaoqin.doc
//fileName     自定义文件名字加后缀（如：考勤.doc）
//filePath     文件存放路径如： E：20161

public static void downfile(string downloadUrl,string filename,string filepath)        
{            
    HttpWebRequest hwr = (HttpWebRequest)WebRequest.Create(downloadUrl);            
    hwr.Timeout = 15000;            
    HttpWebResponse hwp = (HttpWebResponse)hwr.GetResponse();            
    Stream ss = hwp.GetResponseStream();            
    byte[] buffer = new byte[10240];            
    if (!Directory.Exists(filepath))            
    {                
        Directory.CreateDirectory(filepath);            
    }            
    FileStream fs = new FileStream(                
    string.Format(filepath + @"" + filename),                
    FileMode.Create);            
    try            
    {                
        int i;                
        while ((i = ss.Read(buffer, 0, buffer.Length)) >0)                
        {                    
        fs.Write(buffer, 0, i);                
        }                
        fs.Close();                
        ss.Close();            
    }            
    catch (Exception)            
    {                                
        throw;            
    }        
}