C#在WinForm下使用HttpWebRequest上传文件

在 C# WinForm 应用程序中，可以使用 HttpWebRequest 类来实现文件上传，具体步骤如下：

1. 创建 HttpWebRequest 对象，并设置请求参数。

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uploadUrl);
request.Method = "POST";
request.ContentType = "multipart/form-data";

2. 构造要上传的文件数据。

byte[] fileData = File.ReadAllBytes(filePath);
string fileName = Path.GetFileName(filePath);
string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: application/octet-stream\r\n\r\n";
string formdata = string.Format(formdataTemplate, "file", fileName);
byte[] formdataBytes = Encoding.UTF8.GetBytes(formdata);
byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");

3. 将文件数据写入请求流中。

Stream requestStream = request.GetRequestStream();
requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);
requestStream.Write(formdataBytes, 0, formdataBytes.Length);
requestStream.Write(fileData, 0, fileData.Length);
byte[] trailer = Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
requestStream.Write(trailer, 0, trailer.Length);
requestStream.Close();

4. 发送请求并获取响应。

HttpWebResponse response = (HttpWebResponse)request.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
string responseString = reader.ReadToEnd();
reader.Close();
response.Close();

完整的代码示例如下：

public void UploadFile(string uploadUrl, string filePath)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uploadUrl);
    request.Method = "POST";
    request.ContentType = "multipart/form-data";

    byte[] fileData = File.ReadAllBytes(filePath);
    string fileName = Path.GetFileName(filePath);
    string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
    string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: application/octet-stream\r\n\r\n";
    string formdata = string.Format(formdataTemplate, "file", fileName);
    byte[] formdataBytes = Encoding.UTF8.GetBytes(formdata);
    byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");

    Stream requestStream = request.GetRequestStream();
    requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);
    requestStream.Write(formdataBytes, 0, formdataBytes.Length);
    requestStream.Write(fileData, 0, fileData.Length);
    byte[] trailer = Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
    requestStream.Write(trailer, 0, trailer.Length);
    requestStream.Close();

    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    StreamReader reader = new StreamReader(response.GetResponseStream());
    string responseString = reader.ReadToEnd();
    reader.Close();
    response.Close();
}