微信三方平台开发上传base64格式图片至临时素材

 1   public string UploadImgByB64(string b64)
 2         {
 3             //access_token 需要自己获取
 4             string access_token = getToken();
 5             string url = $"https://api.weixin.qq.com/cgi-bin/media/upload?access_token={access_token}&type=image";
 6             byte[] data = Convert.FromBase64String(b64);
 7             var boundary = "fbce142e-4e8e-4bf3-826d-cc3cf506cccc";
 8             var client = new HttpClient();
 9             client.DefaultRequestHeaders.Add("User-Agent", "KnowledgeCenter");
10             client.DefaultRequestHeaders.Remove("Expect");
11             client.DefaultRequestHeaders.Remove("Connection");
12             client.DefaultRequestHeaders.ExpectContinue = false;
13             client.DefaultRequestHeaders.ConnectionClose = true;
14             var content = new MultipartFormDataContent(boundary);
15             content.Headers.Remove("Content-Type");
16             content.Headers.TryAddWithoutValidation("Content-Type", "multipart/form-data; boundary=" + boundary);
17             var contentByte = new ByteArrayContent(data);
18             content.Add(contentByte);
19             contentByte.Headers.Remove("Content-Disposition");
20             contentByte.Headers.TryAddWithoutValidation("Content-Disposition", $"form-data; name=\"media\";filename=\"{Guid.NewGuid()}.png\"" + "");
21             contentByte.Headers.Remove("Content-Type");
22             contentByte.Headers.TryAddWithoutValidation("Content-Type", "image/png");
23             try
24             {
25                 var result2 = client.PostAsync(url, content);
26                 if (result2.Result.StatusCode != HttpStatusCode.OK)
27                     throw new Exception(result2.Result.Content.ReadAsStringAsync().Result);
28                 string jsonstr = result2.Result.Content.ReadAsStringAsync().Result;
29                 var dic = Newtonsoft.Json.Linq.JObject.Parse(jsonstr);
30                 return dic["media_id"].ToString();
31             }
32             catch (Exception ex)
33             {
34                 return null;
35             }
36         }