asp.net 图片加图片水印

<form id="form1" runat="server">
    <div>

        <asp教程:fileupload id="uploadfile" runat="server" />
        <asp:button id="button1" runat="server" onclick="button1_click" text="button" />

    </div>
    </form>

default.aspx.cs

using system;
using system.configuration;
using system.data;
using system.linq;
using system.web;
using system.web.security;
using system.web.ui;
using system.web.ui.htmlcontrols;
using system.web.ui.webcontrols;
using system.web.ui.webcontrols.webparts;
using system.xml.linq;
using system.drawing;
using system.io;
public partial class _default : system.web.ui.page
{
    protected void page_load(object sender, eventargs e)
    {

    }


    protected void button1_click(object sender, eventargs e)
    {
        if (uploadfile.postedfile.filename.trim() != "")
        {
            //上传文件
            string extension = path.getextension(uploadfile.postedfile.filename).toupper();
            string filename = datetime.now.year.tostring() + datetime.now.month.tostring() + datetime.now.day.tostring() + datetime.now.hour.tostring() + datetime.now.minute.tostring() + datetime.now.second.tostring();
            string path = server.mappath(".") + "/uploadfile/" + filename + extension;
            uploadfile.postedfile.saveas(path);

            ////加文字水印，注意，这里的代码和以下加图片水印的代码不能共存
            //system.drawing.image image = system.drawing.image.fromfile(path);
            //graphics g = graphics.fromimage(image);
            //g.drawimage(image, 0, 0, image.width, image.height);
            //font f = new font("verdana", 32);
            //brush b = new solidbrush(color.white);
            //string addtext = addtext.value.trim();
            //g.drawstring(addtext, f, b, 10, 10);
            //g.dispose();

            //加图片水印
            system.drawing.image image = system.drawing.image.fromfile(path);
            system.drawing.image copyimage = system.drawing.image.fromfile(server.mappath(".") + "/tp.gif");
            graphics g = graphics.fromimage(image);
            g.drawimage(copyimage, new rectangle(image.width - copyimage.width, image.height - copyimage.height, copyimage.width, copyimage.height), 0, 0, copyimage.width, copyimage.height, graphicsunit.pixel);
            g.dispose();

            //保存加水印过后的图片,删除原始图片
            string newpath = server.mappath(".") + "/uploadfile/" + filename + "_new" + extension;
            image.save(newpath);
            image.dispose();
            if (file.exists(path))
            {
                file.delete(path);
            }

           // response.redirect(newpath);
            response.redirect("default.aspx");
        }
    }
}

补充：asp.net教程,.Net开发