关于VB.NET HttpClient上传附件的问题！(语言-java)

以下是我需要优化的问题:

VB.NET HttpClient上传附件的问题:

Dim filename = Path.GetFileName(file)
Dim client As HttpClient = New HttpClient()
Dim postData As List(Of KeyValuePair(Of String, String)) = New List(Of KeyValuePair(Of String, String))
postData.Add(New KeyValuePair(Of String, String)("filename", filename))

Dim content As HttpContent = New FormUrlEncodedContent(postData)
content.Headers.ContentType.MediaType = "multipart/form-data"
Dim response = Await client.PostAsync("http://huseeyon.gnway.cc:8088/seeyon/rest/attachment?token=6a7bf657-1733-4751-b4aa-ca7a49739ab6", content)

response.EnsureSuccessStatusCode()
Dim responseBody As String = Await response.Content.ReadAsStringAsync()
Console.WriteLine(responseBody)

手工增加Headers.ContentType会报错提示. the request was rejected because no multipart boundary was found
不增加Headers.ContentType则提示http415，求解决

【以下回答由 GPT 生成】

该问题的根本原因是没有正确设置请求中的multipart boundary。下面是解决该问题的具体步骤：

1. 首先需要引用System.Net.Http和System.Net.Http.Headers命名空间。

2. 创建一个MultipartFormDataContent对象，用于添加要上传的文件数据和其他参数。将文件名添加到表单数据中：

Dim formData As MultipartFormDataContent = New MultipartFormDataContent()
formData.Add(New StringContent(filename), "filename")

1. 创建一个HttpClient对象并发送POST请求。确保设置请求的Content-Type头部为"multipart/form-data"：

Dim client As HttpClient = New HttpClient()
client.DefaultRequestHeaders.Accept.Add(New MediaTypeWithQualityHeaderValue("application/json"))
Dim response = Await client.PostAsync("http://huseeyon.gnway.cc:8088/seeyon/rest/attachment?token=6a7bf657-1733-4751-b4aa-ca7a49739ab6", formData)

1. 最后，根据服务器响应进行适当的处理。

完整的代码示例：

Imports System.Net.Http
Imports System.Net.Http.Headers

...

Dim filename = Path.GetFileName(file)
Dim formData As MultipartFormDataContent = New MultipartFormDataContent()
formData.Add(New StringContent(filename), "filename")

Dim client As HttpClient = New HttpClient()
client.DefaultRequestHeaders.Accept.Add(New MediaTypeWithQualityHeaderValue("application/json"))
Dim response = Await client.PostAsync("http://huseeyon.gnway.cc:8088/seeyon/rest/attachment?token=6a7bf657-1733-4751-b4aa-ca7a49739ab6", formData)

response.EnsureSuccessStatusCode()
Dim responseBody As String = Await response.Content.ReadAsStringAsync()
Console.WriteLine(responseBody)

请注意，设置请求的Content-Type头部应该是通过添加Accept头部来实现，HttpClient会自动处理Content-Type的生成。此外，确保文件在指定路径(file变量)中存在。