C#动态生成带参数的小程序二维码

应用场景

在微信小程序管理后台，我们可以生成下载标准的小程序二维码，提供主程序入口功能。在实际应用开发中，小程序二维码是可以携带参数的，可以动态进行生成，如如下场景：

1、不同参数决定的显示界面不同。

2、不同参数决定的功能不同。

3、由于小程序审核机制，我们将不同的应用集成在一个小程序里，通过不同的参数进行入口控制。

关键代码

操作界面

我们以一种验证、绑定手机的小程序功能为例，该小程序可以生成动态校验码，以实现实际业务应用的其它场景。界面中我们设计了提示信息Label，生成按钮 Button 和扫码图片 Image 等Asp.net控件。

示例界面如下，通过点击按钮，动态生成二维码图片，该参数将引导用户进入动态码生成功能：

示例UI代码如下：

<div class="user-box"><span>验证手机</span><br><br><div class="query-box"><label>扫描二维码获取动态校验码</label><br><label>建议您PC注册,如果微信,可常按并选择前往图中包含的小程序打开(某些手机系统可能不支持此操作)</label></div><br><br><asp:Button ID="createCode" Text="新注册或换手机号点这里生成以获取动态校验码" Visible="true" CssClass="form-control"runat="server" OnClick="createCode_Click"></asp:Button></div><div class="user-box" id="ecodepanel" align="center" visible="false" runat="server"><br /><asp:Image ID="ecode" Width="200px" Height="200px" Visible="false" runat="server"></asp:Image><br><span style='color: silver'></span><br><br></div>

服务端点击事件

点击按钮，通过设置参数值，并访问腾讯API，生成小程序二维码，转换为图片BASE64编码，如果生成成功则显示在Image控件里，点击事件的，示例代码如下：

protected void createCode_Click(object sender, EventArgs e){string paras = "reqvmobile";    //参数值设置//可以更改小程序二维码的色系int r = 4;int g = 128;int b = 188;ecode.ImageUrl = getBase64(255, r, g, b);   //将生成成功的BASE64编码赋值给Image控件ecode.Visible = true;ecodepanel.Visible = true;}//获取小程序二维码图片的 Base64值 string getBase64(string paras, int width, int linecolor_R, int linecolor_G, int linecolor_B){string desimg = Request.PhysicalApplicationPath + "\\app_data\\" + System.Guid.NewGuid().ToString() + ".jpg";  //目标图片临时路径//生成二维码图片文件System.IO.File.WriteAllBytes(desimg, getMpBuffer(wxmp_accesstoken, paras, width, linecolor_R, linecolor_G, linecolor_B));string base64 = ImgToBase64String(desimg, true);System.IO.File.Delete(desimg);  //删除临时文件return base64;}//图片转BASE64方法
public string ImgToBase64String(string Imagefilename,bool outFullString=false){try{System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(Imagefilename);MemoryStream ms = new MemoryStream();//            bmp.Save(ms,ImageFormat.Jpeg)System.Drawing.Imaging.ImageFormat iformat = System.Drawing.Imaging.ImageFormat.Jpeg;string extension = System.IO.Path.GetExtension(Imagefilename).Replace(".", "").ToLower();if (extension == "bmp"){iformat = System.Drawing.Imaging.ImageFormat.Bmp;}else if (extension == "emf"){iformat = System.Drawing.Imaging.ImageFormat.Emf;}else if (extension == "exif"){iformat = System.Drawing.Imaging.ImageFormat.Exif;}else if (extension == "gif"){iformat = System.Drawing.Imaging.ImageFormat.Gif;}else if (extension == "icon"){iformat = System.Drawing.Imaging.ImageFormat.Icon;}else if (extension == "png"){iformat = System.Drawing.Imaging.ImageFormat.Png;}else if (extension == "tiff"){iformat = System.Drawing.Imaging.ImageFormat.Tiff;}else if (extension == "wmf"){iformat = System.Drawing.Imaging.ImageFormat.Wmf;}bmp.Save(ms, iformat);byte[] arr = new byte[ms.Length];ms.Position = 0;ms.Read(arr, 0, (int)ms.Length);ms.Close();bmp.Dispose();string rv=Convert.ToBase64String(arr);if (outFullString == true){rv = "data:image/" + extension + ";base64," + rv;}return rv;}catch (Exception ex){return null;}}

生成小程序二维码

getMpBuffer(wxmp_accesstoken, paras, width, linecolor_R, linecolor_G, linecolor_B)方法返回byte[]类型，参数需要传递通过小程序Appid和AppSecret生成的合法令牌值；动态参数值；图像宽度；R/G/B的色系值。

方法代码如下：

public byte[] getMpBuffer(string access_token, string scene, int width, int linecolor_R, int linecolor_G, int linecolor_B){var url = string.Format("https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token={0}", access_token);var postData = "{\"scene\":\"" + scene + "\",\"width\":" + width.ToString() + ",\"line_color\":{\"r\":" + linecolor_R.ToString() + ",\"g\":" + linecolor_G.ToString() + ",\"b\":" + linecolor_B.ToString() + "}}";System.Net.HttpWebRequest request;request = (System.Net.HttpWebRequest)WebRequest.Create(url);request.Method = "POST";request.ContentType = "application/json;charset=UTF-8";byte[] payload;payload = System.Text.Encoding.UTF8.GetBytes(postData);request.ContentLength = payload.Length;Stream writer = request.GetRequestStream();writer.Write(payload, 0, payload.Length);writer.Close();System.Net.HttpWebResponse response;response = (System.Net.HttpWebResponse)request.GetResponse();System.IO.Stream stream;stream = response.GetResponseStream();List<byte> bytes = new List<byte>();int temp = stream.ReadByte();while (temp != -1){bytes.Add((byte)temp);temp = stream.ReadByte();}byte[] result = bytes.ToArray();return result;}