Develop Reference

Uploading multipart form files with HttpClient

I am trying to create an attachment using the Support Bee API as documented here:
https://supportbee.com/api#create_attachment
I have written a service that uses an HttpClient to create and send the request using a filename.
If I test in in Postman, it succeeds. I am using form-data for the body and just selecting the file to upload from the UI:
It doesn't work when I try to upload it via my HttpClient Service:
public async Task<string> CreateAttachmentAsync(string fileName)
{
// "client" is HttpClient provided via D.I.
MultipartFormDataContent content = new MultipartFormDataContent();
content.Add(new StreamContent(new FileStream(fileName, FileMode.Open)), "files[]");
using (HttpResponseMessage response = await client.PostAsync(
"https://xxx.supportbee.com/attachments?auth_token=xxx",
content))
{
string responseString = await response.Content.ReadAsStringAsync();
return responseString;
}
}
This results in a 500 Internal Server Error. Inspecting the MultipartFormDataContent object I can see that it's header values are automatically being set:
{
Content-Type: multipart/form-data; boundary="c9be3778-4de5-4460-9929-adcaa6bdda79"
Content-Length: 164
}
I have also tried reading the file to a byte array first and using ByteArrayContent instead of StreamContent to no avail. The response doesn't provide anything helpful, but since the request works in Postman I must have something wrong with my code, but I don't know what else to try.
Edit: I tested with Fiddler to compare the successful Postman request to my code. Here is the request with Postman:
POST
https://xxx.supportbee.com/attachments?auth_token=xxx
HTTP/1.1 User-Agent: PostmanRuntime/7.22.0 Accept: / Cache-Control:
no-cache Postman-Token: f84d22fa-b4b1-4bf5-b183-916a786c6385 Host:
xx.supportbee.com Content-Type: multipart/form-data;
boundary=--------------------------714700821471353664787346
Accept-Encoding: gzip, deflate, br Content-Length: 241 Connection:
close
----------------------------714700821471353664787346 Content-Disposition: form-data; name="files[]"; filename="sample.txt"
Content-Type: text/plain
This contains example text.
----------------------------714700821471353664787346--
And the failing request from my code:
POST
https://xxx.supportbee.com/attachments?auth_token=xxx
HTTP/1.1 Host: xxx.supportbee.com Accept: / Accept-Encoding:
gzip, deflate, br Connection: close Content-Type: multipart/form-data;
boundary="ea97cbc1-70ea-4cc4-9801-09f5feffc763" Content-Length: 206
--ea97cbc1-70ea-4cc4-9801-09f5feffc763 Content-Disposition: form-data; name="files[]"; filename=sample; filename*=utf-8''sample
This contains example text.
--ea97cbc1-70ea-4cc4-9801-09f5feffc763--
The difference I can see is that the individual part in Postman has its own Content-Type: text/plain header for the file, and mine doesn't. I'm unable to add this because if I try content.Headers.Add("Content-Type", "text/plain"); It fails with 'Cannot add value because header 'Content-Type' does not support multiple values.'

First, it's important to note that a 500 response is akin to an unhandled exception, i.e. it's a bug on their end and more or less impossible to know for sure what you did wrong. I would suggest reporting it to them and, although I'm not familiar with Support Bee, I would hope they have good support people who can help you troubleshoot. :)
But if you want to play the guessing game, I agree that subtle differences between your successful Postman call and your code are a good place to start. For that header, note that content is the MultipartFormDataContent. You actually want to set it on the StreamContent object.
Also, look at the request headers Postman is sending and see if Content-Disposition includes a filename. You might need to add that to your code too, if the API is expecting it.
Here's how to do both:
var fileContent = new StreamContent(File.OpenRead(path));
fileContent.Headers.ContentType = new MediaTypeHeaderValue("text/plain");
content.Add(fileContent, "files[]", Path.GetFileName(path));
If that's not the problem, look at the "raw" version of the request body in Postman, as well as those 11 request headers, and see if you can spot anything else you might be missing.

How to make multipart/mixed request containing nested HTTP requests

I am trying to implement creating a multipart request where each part is a HTTP request
To see what I mean here's for example how this Google API works: https://cloud.google.com/dns/api/batch#example (I don't use that API, it's just an example)
I've seen examples using MultipartFormDataContent but I don't understand how to create each part"
--====1340674896===
Content-Type: application/http
Content-Transfer-Encoding: binary
Content-ID: 1111
POST /contacts/479038 HTTP/1.1
Content-Type: application/json
Accept: application/json
{ "SomeData" : 1 }
The content of each part is I think the serialized string of a request:
GET /contacts/479038 HTTP/1.1
Content-Type: application/json
Accept: application/json
{ "SomeData" : 1 }
So how do I create this? I guess I need to get the serialized version of a HttpRequestMessage?
Can I just serialize request.Content.ReadAsStringAsync())
In WebAPI I see there's this HttpContentMessage which takes a HttpRequestMessage and can serialize it:
var httpMessageContent = new HttpMessageContent(request);
var buffer = httpMessageContent.ReadAsByteArrayAsync().Result;
stream.Write(buffer, 0, buffer.Length);
But I don't have this class available in .NETStandard

Filling Parameter with Attribute [FromForm] with Fiddler

I want to test the following method (generated by swagger) with fiddler:
[HttpPost]
[Route("/webservice/images")]
[SwaggerOperation("UploadImage")]
[SwaggerResponse(200, type: typeof(ResourceIdEntry))]
public virtual IActionResult UploadImage([FromForm] Stream image)
{
return new ObjectResult();
}
I configure Fiddler to send a POST to http://localhost:50352/webservice/images with the Header
Content-Type: multipart/form-data; boundary=-------------------------acebdf13572468
User-Agent: Fiddler
Host: localhost:50352
Content-Length: 12931
and the body
---------------------------acebdf13572468
Content-Disposition: form-data; name="image"; filename="Test.tif"
Content-Type: image/tiff
<#INCLUDE *C:\...\Test.tif*#>
---------------------------acebdf13572468--
but UploadImage is not even called and I just get a 500 returned. If I remove the image parameter, the Method gets at least called. How do I have to configure fiddler so that the call is resolved correctly?

Checkout the following post around uploading file with web api - https://learn.microsoft.com/en-us/aspnet/web-api/overview/advanced/sending-html-form-data-part-2
There is no built in media formatter for dealing with multi part form posts. However this is nothing stopping you writing your own so the same logic can be applied to multiple actions, here is a gist example of a custom formatter - https://gist.github.com/Danielku15/bfc568a19b9e58fd9e80

[FromBody]JToken param is null when ContentType: application/json or it's bad serialized when Contenttype: application/x-www-form-urlencoded [Fiddler]

As the topic says, I've faced with a problem while trying to call an endpoint (POST) with a Request Body via Fiddler.
There is a http api method:
[HttpPost]
[Route("books")]
public IHttpActionResult GetBooks([FromBody]JToken filterRequest)
{...}
In Fiddler I make a POST call with request header:
User-Agent: Fiddler
Host: localhost
Content-Length: 21
Content-Type: application/json
And the Request Body looks like: { "title" : "Harry Potter"}. While debugging it, I get null filterRequest parameter.
But when I use Content-Type: application/x-www-form-urlencoded, parameter filterRequest parameter is not null but unfortunately contains incorrect syntax like:
{{"{ \"title\" : \"Harry Potter\"}": ""}}
And it's wrong serialized by:
var columnsFilter = new JavaScriptSerializer().Deserialize<Dictionary<string, string>>(filter);
I have no idea what I am doing wrong here. Maybe do you have met with similar problem and could help?

It turned out that the whole problem was based on wrong quotes. I had to use just ' and the posted request body was correct with Content-Type: application/json.

Send multiple of items to WCF Dataservice at once?

I'm using WCF Data Service as a way to allow other webservice in the project to connect to the database. My problem is that I our project has a crawler that add tens of items to the database every hour.
Using AddToItems method (which is auto generated by ADO.NET) leads to timeout exception or at least it makes the crawler in need to wait for a lot of time taking into consideration that Addto method handles each independently.
*Notes :
1- I've added an interceptor on adding to items to perform some actions when a new item is added.
2- WCF Data services Service Operations doesn't allow taking parameters of a user defined data type , that prevented me from creating a service operation that takes a list of items as a parameter to be able to handle multiple items at each time and at the same way to allow the client to handle it asynchronously.
When I tried to serialize this list so it can be treated as a string , an exception has occurred because of the length limit of the url even when POST is used instead of Get.
Update : Saveing Changes via BeginSaveChanged and EndSaveChanged solved the problem to some extent but I'm still looking for a better solution

Maybe the OData feature Batch can address your requirement:
var client = new Container(serviceUrl);
client.Format.UseJson();
DefaultBatchCustomer customer0ToAdd = new DefaultBatchCustomer { Id = 10, Name = "Customer 10" };
DefaultBatchCustomer customer0ToAdd = new DefaultBatchCustomer { Id = 11, Name = "Customer 11" };
client.AddToDefaultBatchCustomer(customer0ToAdd);
client.AddToDefaultBatchCustomer(customer1ToAdd);
var response = await client.SaveChangesAsync(SaveChangesOptions.BatchWithSingleChangeset);
and the request looks like:
POST http://jinfutanwebapi1:9123/DefaultBatch/$batch HTTP/1.1
OData-Version: 4.0;NetFx
OData-MaxVersion: 4.0;NetFx
Content-Type: multipart/mixed; boundary=batch_8ce61768-e8bb-4117-954b-9bc43e05baef
Accept: multipart/mixed
Accept-Charset: UTF-8
User-Agent: Microsoft ADO.NET Data Services
Host: jinfutanwebapi1:9123
Content-Length: 1772
Expect: 100-continue
--batch_8ce61768-e8bb-4117-954b-9bc43e05baef
Content-Type: multipart/mixed; boundary=changeset_b36bec94-fc3b-4d89-99cc-0610fcec8148
--changeset_b36bec94-fc3b-4d89-99cc-0610fcec8148
Content-Type: application/http
Content-Transfer-Encoding: binary
POST http://jinfutanwebapi1:9123/DefaultBatch/DefaultBatchCustomer HTTP/1.1
Content-ID: 13
OData-Version: 4.0;NetFx
OData-MaxVersion: 4.0;NetFx
Content-Type: application/json;odata.metadata=minimal
Accept: application/json;odata.metadata=minimal
Accept-Charset: UTF-8
User-Agent: Microsoft ADO.NET Data Services
{"#odata.type":"#WebStack.QA.Test.OData.Batch.Tests.DataServicesClient.DefaultBatchCustomer","Id":10,"Name":"Customer 10"}
--changeset_b36bec94-fc3b-4d89-99cc-0610fcec8148
Content-Type: application/http
Content-Transfer-Encoding: binary
POST http://jinfutanwebapi1:9123/DefaultBatch/DefaultBatchCustomer HTTP/1.1
Content-ID: 14
OData-Version: 4.0;NetFx
OData-MaxVersion: 4.0;NetFx
Content-Type: application/json;odata.metadata=minimal
Accept: application/json;odata.metadata=minimal
Accept-Charset: UTF-8
User-Agent: Microsoft ADO.NET Data Services
{"#odata.type":"#WebStack.QA.Test.OData.Batch.Tests.DataServicesClient.DefaultBatchCustomer","Id":11,"Name":"Customer 11"}
--changeset_b36bec94-fc3b-4d89-99cc-0610fcec8148--
--batch_8ce61768-e8bb-4117-954b-9bc43e05baef--