转自:http://www.cnblogs.com/JuneZhang/p/3926679.html
string url = string.Format(@"http://webservice.36wu.com/DimensionalCodeService.asmx/GetCodeImgByString?size={0}&content={1}", 5, 123456);
System.Net.WebRequest webreq = System.Net.WebRequest.Create(url);
System.Net.WebResponse webres = webreq.GetResponse();
using(System.IO.Stream stream = webres.GetResponseStream())
{
pictureBox1.Image = Image.FromStream(stream);
}