using system; using system.collections.generic; using system.linq; using system.web; using system.web.ui; using system.web.ui.webcontrols; using system.drawing; namespace 学生在线考试系统 { public partial class ajaxautocode : system.web.ui.page { //验证数字 public string authcode = string.empty; protected void page_load(object sender, eventargs e) { #region 第一种产生验证码的方法 random random = new random(); authcode = random.next(1111, 9999).tostring(); //构造图片 bitmap image = new bitmap(authcode.length * 12, 25); //创建画布 graphics g = graphics.fromimage(image); try { g.clear(color.white); for (int i = 0; i < 25; i++) { int x1 = random.next(image.width); int x2 = random.next(image.width); int y1 = random.next(image.height); int y2 = random.next(image.height); //链接两点的线条 g.drawline(new pen(color.silver), x1, y1, x2, y2); } font font = new font("arial", 12, fontstyle.bold | fontstyle.italic); system.drawing.drawing2d.lineargradientbrush brush = new system.drawing.drawing2d.lineargradientbrush( new rectangle(0, 0, image.width, image.height), color.blue, color.darkblue, 1.2f, true); g.drawstring(authcode, font, brush, 2, 2); //画图片的前景噪点 for (int i = 0; i < 100; i++) { int x = random.next(image.width); int y = random.next(image.height); image.setpixel(x, y, color.fromargb(random.next())); } g.drawrectangle(new pen(color.silver), 0, 0, image.width - 1, image.height - 1); system.io.memorystream ms = new system.io.memorystream(); image.save(ms, system.drawing.imaging.imageformat.gif); ms.writeto(this.response.outputstream); ms.close(); this.response.contenttype = "image/gif"; } finally { image.dispose(); g.dispose(); } #endregion } } }
2、其次在显示验证码的页面定义一个js函数
function fgetcode() { document.getelementbyid("getcode").src="default2.aspx?"+math.random(); }
3.再编辑前台页面aspx,下面是前台页面的代码片段
<label>验证码</label> <asp:textbox id="txt_checkcode" runat="server" width="178px"></asp:textbox> <img src="default2.aspx" alt="看不清楚？" id="getcode"/> <a href="javascript:fgetcode()">更换验证码</a>
更多asp.net ajax实现无刷新验证码。