我试图通过API以编程方式将图像上传到另一台服务器. API希望我在一个字节数组中上传图像,以便在字段中发送：“image_content”.
我的实现和调用代码如下. Web请求命中服务器,但服务器响应我的Web请求中不存在该图像.
当我运行以下代码时,我收到的错误是图像不在请求中.我在这里错过了什么？
public static class FormUpload
{
private static readonly Encoding encoding = Encoding.UTF8;
public static HttpWebResponse MultipartFormDataPost(string postUrl, string userAgent, Dictionary postParameters)
{
string formDataBoundary = String.Format(“———-{0:N}”, Guid.NewGuid());
string contentType = “multipart/form-data; boundary=” formDataBoundary;
byte[] formData = GetMultipartFormData(postParameters, formDataBoundary);
return PostForm(postUrl, userAgent, contentType, formData);
}
private static HttpWebResponse PostForm(string postUrl, string userAgent, string contentType, byte[] formData)
{
HttpWebRequest request = WebRequest.Create(postUrl) as HttpWebRequest;
if (request == null)
{
throw new NullReferenceException(“request is not a http request”);
}
// Set up the request properties.
request.Method = “POST”;
request.ContentType = contentType;
request.UserAgent = userAgent;
request.ContentLength = formData.Length;
// Send the form data to the request.
using (Stream requestStream = request.GetRequestStream())
{
requestStream.Write(formData, 0, formData.Length);
requestStream.Close();
}
return request.GetResponse() as HttpWebResponse;
}
private static byte[] GetMultipartFormData(Dictionary postParameters, string boundary)
{
Stream formDataStream = new System.IO.MemoryStream();
bool needsCLRF = false;
foreach (var param in postParameters)
{
if (param.Value is FileParameter)
{
FileParameter fileToUpload = (FileParameter)param.Value;
// Add just the first part of this param, since we will write the file data directly to the Stream
string header = string.Format(“–{0}\r\nContent-Disposition: form-data; name=\”{1}\”; filename=\”{2}\”\r\nContent-Type: {3}\r\n\r\n”,
boundary,
param.Key,
fileToUpload.FileName ?? param.Key,
fileToUpload.ContentType ?? “application/octet-stream”);
formDataStream.Write(encoding.GetBytes(header), 0, encoding.GetByteCount(header));
// Write the file data directly to the Stream, rather than serializing it to a string.
formDataStream.Write(fileToUpload.File, 0, fileToUpload.File.Length);
}
else
{
string postData = string.Format(“–{0}\r\nContent-Disposition: form-data; name=\”{1}\”\r\n\r\n{2}”,
boundary,
param.Key,
param.Value);
formDataStream.Write(encoding.GetBytes(postData), 0, encoding.GetByteCount(postData));
}
}
// Add the end of the request. Start with a newline
string footer = “\r\n–” boundary “–\r\n”;
formDataStream.Write(encoding.GetBytes(footer), 0, encoding.GetByteCount(footer));
// Dump the Stream into a byte[]
formDataStream.Position = 0;
byte[] formData = new byte[formDataStream.Length];
formDataStream.Read(formData, 0, formData.Length);
formDataStream.Close();
return formData;
}
public class FileParameter
{
public byte[] File { get; set; }
public string FileName { get; set; }
public string ContentType { get; set; }
public FileParameter(byte[] file) : this(file, null) { }
public FileParameter(byte[] file, string filename) : this(file, filename, null) { }
public FileParameter(byte[] file, string filename, string contenttype)
{
File = file;
FileName = filename;
ContentType = contenttype;
}
}
}
调用上述函数的代码是：
// Read file data
FileStream fs = new FileStream(“c:\\myimage.jpeg”, FileMode.Open, FileAccess.Read);
byte[] data = new byte[fs.Length];
fs.Read(data, 0, data.Length);
fs.Close();
// Generate post objects
Dictionary postParameters = new Dictionary();
postParameters.Add(“image_content”,data);
// Create request and receive response
string postURL = “myurl”;
string userAgent = “Mozilla”;
HttpWebResponse webResponse = FormUpload.MultipartFormDataPost(postURL, userAgent, postParameters);
// Process response
StreamReader responseReader = new StreamReader(webResponse.GetResponseStream());
string fullResponse = responseReader.ReadToEnd();
webResponse.Close();
Response.Write(fullResponse);
解决方法:
在我看来,你应该使用MultipartFormDataContent类,因为它“为使用multipart / form-data MIME类型编码的内容提供容器.”.试试这个
public static HttpWebResponse MultipartFormDataPost(string postUrl, string userAgent, byte[] data)
{
string contentType;
byte[] formData = Program.GetMultipartFormData(data, out contentType);
return PostForm(postUrl, userAgent, contentType, formData);
}
public static byte[] GetMultipartFormData(byte[] data, out string contentType)
{
var byteArrayContent = new ByteArrayContent(data);
byteArrayContent.Headers.ContentType = new MediaTypeHeaderValue(“image/jpeg”);
byteArrayContent.Headers.Add(“image_content”, “myimage.jpeg”);
var content = new MultipartFormDataContent(String.Format(“———-{0:N}”, Guid.NewGuid())) { byteArrayContent };
contentType = content.Headers.ContentType.ToString();
return content.ReadAsByteArrayAsync().Result;
}
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