HttpResponseMessage 内容未返回正确的内容类型

Question

I am trying to return an Xml File and a Class as JSON from my web api as part of business requirements as they do not like to send XML within JSON.

But the content type of the response is not "multipart/form-data"

API Code C#.Net Core

        [HttpPost("GetMessage")]
    public HttpResponseMessage GetMessage([FromForm]BaseInput baseInput)
    {
        MultipartContent MultiContent = new MultipartContent("form-data");
        HttpResponseMessage ResponseMessage = new HttpResponseMessage();

        StringContent contentMessageJSON = CreateJSONContent(JsonConvert.SerializeObject(rtnVal));
        StringContent contentMessagexml = CreateBusinessMessageContent(rtnVal.MessageXML, "BUSINESSMESSAGE.XML");

        MultiContent.Add(contentMessagexml);
        MultiContent.Add(contentMessageJSON);
        ResponseMessage.Content = MultiContent;

        return ResponseMessage;
    }


public StringContent CreateJSONContent(string strJSON)
    {
        StringContent contentData;
        contentData = new StringContent(strJSON);
        try
        {
            contentData.Headers.Remove("Content-Type");
            contentData.Headers.TryAddWithoutValidation("Content-Transfer-Encoding", "binary");
            contentData.Headers.TryAddWithoutValidation("Content-ID", Guid.NewGuid().ToString());
            contentData.Headers.TryAddWithoutValidation("Content-Disposition", "form-data;name=METADATA");
        }
        catch (Exception ex)
        {
        }
        return contentData;
    }

    public StringContent CreateBusinessMessageContent(string businessmessage, string filename)
    {
        StringContent contentMessagexml = new StringContent(businessmessage);
        try
        {
            contentMessagexml.Headers.Remove("Content-Type");
            contentMessagexml.Headers.TryAddWithoutValidation("Content-Disposition", string.Format("form-data; name=BUSINESSMESSAGE; filename={0}", filename));
            contentMessagexml.Headers.TryAddWithoutValidation("Content-Type", "text/xml");
        }
        catch (Exception ex)
        {
        }
        return contentMessagexml;
    }

Client Code VB Winforms

        Dim httpresponse As HttpResponseMessage

        'Now send it
        Try

            httpresponse = Await httpClient.PostAsync(txtEndPoint.Text, content)
            Dim MultiPartStreamProv As MultipartStreamProvider = Await httpresponse.Content.ReadAsMultipartAsync()

            Dim stringContent = Await MultiPartStreamProv.Contents(0).ReadAsStringAsync()
            Dim streamContent = Await MultiPartStreamProv.Contents(1).ReadAsStreamAsync()
        Catch ex As Exception

        End Try

In The Client Code, i get the error "Invalid 'HttpContent' instance provided. It does not have a content type header starting with 'multipart/'. Parameter name: content"

i Checked and the content type is Application/json, no idea why.

Answer 1

I am trying to return an Xml File and a Class as JSON from my web api as part of business requirements as they do not like to send XML within JSON.

But the content type of the response is not "multipart/form-data"

API Code C#.Net Core

        [HttpPost("GetMessage")]
    public HttpResponseMessage GetMessage([FromForm]BaseInput baseInput)
    {
        MultipartContent MultiContent = new MultipartContent("form-data");
        HttpResponseMessage ResponseMessage = new HttpResponseMessage();

        StringContent contentMessageJSON = CreateJSONContent(JsonConvert.SerializeObject(rtnVal));
        StringContent contentMessagexml = CreateBusinessMessageContent(rtnVal.MessageXML, "BUSINESSMESSAGE.XML");

        MultiContent.Add(contentMessagexml);
        MultiContent.Add(contentMessageJSON);
        ResponseMessage.Content = MultiContent;

        return ResponseMessage;
    }


public StringContent CreateJSONContent(string strJSON)
    {
        StringContent contentData;
        contentData = new StringContent(strJSON);
        try
        {
            contentData.Headers.Remove("Content-Type");
            contentData.Headers.TryAddWithoutValidation("Content-Transfer-Encoding", "binary");
            contentData.Headers.TryAddWithoutValidation("Content-ID", Guid.NewGuid().ToString());
            contentData.Headers.TryAddWithoutValidation("Content-Disposition", "form-data;name=METADATA");
        }
        catch (Exception ex)
        {
        }
        return contentData;
    }

    public StringContent CreateBusinessMessageContent(string businessmessage, string filename)
    {
        StringContent contentMessagexml = new StringContent(businessmessage);
        try
        {
            contentMessagexml.Headers.Remove("Content-Type");
            contentMessagexml.Headers.TryAddWithoutValidation("Content-Disposition", string.Format("form-data; name=BUSINESSMESSAGE; filename={0}", filename));
            contentMessagexml.Headers.TryAddWithoutValidation("Content-Type", "text/xml");
        }
        catch (Exception ex)
        {
        }
        return contentMessagexml;
    }

Client Code VB Winforms

        Dim httpresponse As HttpResponseMessage

        'Now send it
        Try

            httpresponse = Await httpClient.PostAsync(txtEndPoint.Text, content)
            Dim MultiPartStreamProv As MultipartStreamProvider = Await httpresponse.Content.ReadAsMultipartAsync()

            Dim stringContent = Await MultiPartStreamProv.Contents(0).ReadAsStringAsync()
            Dim streamContent = Await MultiPartStreamProv.Contents(1).ReadAsStreamAsync()
        Catch ex As Exception

        End Try

In The Client Code, i get the error "Invalid 'HttpContent' instance provided. It does not have a content type header starting with 'multipart/'. Parameter name: content"

i Checked and the content type is Application/json, no idea why.