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Posted 22 Nov 2013


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ASP.NET WebApi: MultipartDataMediaFormatter

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4.93/5 (18 votes)
5 Jun 2017MIT2 min read
Used for binding custom types (including files) when sending and receiving multipart encoded form data


This is a solution for automatic binding action parameters of custom types (including files) encoded as multipart/form-data. It works similar to ASP.NET MVC binding. This media type formatter can be used also for sending objects (using HttpClient) with automatic serialization to multipart/form-data.

This formatter can process:

  • custom non enumerable classes (deeply nested classes supported)
  • all simple types that can be converted from/to string (using TypeConverter)
  • files (MultipartDataMediaFormatter.Infrastructure.HttpFile or byte[])
  • generic arrays
  • generic lists
  • generic dictionaries

Using the Code

Install formatter from Nuget:

Install-Package MultipartDataMediaFormatter.V2

Add it to WebApi formatters collection:

If WebApi is hosted on IIS (on Application Start):

(new FormMultipartEncodedMediaTypeFormatter(new MultipartFormatterSettings()));    

If WebApi is self-hosted:

new HttpSelfHostConfiguration(<url>).Formatters.Add
(new FormMultipartEncodedMediaTypeFormatter(new MultipartFormatterSettings()));      

Using formatter for sending objects (example from test project):

private ApiResult<T> PostModel<T>(T model, string url)
 var mediaTypeFormatter = new FormMultipartEncodedMediaTypeFormatter(new MultipartFormatterSettings()
        SerializeByteArrayAsHttpFile = true,
        CultureInfo = CultureInfo.CurrentCulture,
        ValidateNonNullableMissedProperty = true
 using (new WebApiHttpServer(BaseApiAddress, mediaTypeFormatter))
 using (var client = CreateHttpClient(BaseApiAddress))
 using (HttpResponseMessage response = client.PostAsync(url, model, mediaTypeFormatter).Result)
  if (response.StatusCode != HttpStatusCode.OK)
    var err = response.Content.ReadAsStringAsync().Result;
  var resultModel = response.Content.ReadAsAsync<ApiResult<T>>(new[] { mediaTypeFormatter }).Result;
  return resultModel;

You can use MultipartDataMediaFormatter.Infrastructure.FormData class to access raw http data:

public void PostFileBindRawFormData(MultipartDataMediaFormatter.Infrastructure.FormData formData)
      HttpFile file;
      formData.TryGetValue(<key>, out file);

Bind custom model example:

//model example
public class PersonModel
    public string FirstName {get; set;}
    public string LastName {get; set;}
    public DateTime? BirthDate {get; set;}
    public HttpFile AvatarImage {get; set;}
    public List<HttpFile> Attachments {get; set;}
    public List<PersonModel> ConnectedPersons {get; set;}
    public PersonModel Creator {get; set;}
    public List<string> Attributes {get; set;}

//api controller example
public void PostPerson(PersonModel model)
   //do something with the model

Client http form keys:
* FirstName
* LastName
* BirthDate
* AvatarImage

* Attachments[0]
* Attachments[1]
* ... other Attachments[0...n]

* ConnectedPersons[0].FirstName
* ConnectedPersons[0].LastName
* ... other properties for ConnectedPersons[0] property

* Creator.FirstName
* Creator.LastName
* ... other properties for Creator property

* Attributes[0]
* Attributes[1]
* ... other Attributes[0...n]
 or you can use not indexed names for simple types:
 * Attributes
 * Attributes
 * ... other Attributes



Version 2.0.0 (2017-05-27)

Version 1.0.2 (2016-08-12)

  • Parsing lists of simple types and files with not indexed naming scheme (keys have same names like "propName" or "propName[]")
  • Parsing values "on" and "off" for boolean properties
  • Binding HttpFile from http request as byte[] if model has such property
  • Added class MultipartDataMediaFormatter.Infrastructure.MultipartFormatterSettings to control:
    • CultureInfo
    • Serializing byte[] as HttpFile when sending data
    • Validating non nullable value types properties if there are no appropriate keys in http request

Version 1.0.1 (2014-04-03)

  • Fixed a bug that caused Exception (No MediaTypeFormatter is available to read an object of type <type name>) when posted data use multipart boundary different from used inside formatter code
  • Fixed a bug that caused error when binding model with recursive properties

Version 1.0 (2013-11-22)

  • First release


For successfully running tests from the test project, you should run Visual Studio with administrator rights because of using Self Hosted WebApi Server System.Web.Http.SelfHost.HttpSelfHostServer.


This article, along with any associated source code and files, is licensed under The MIT License


About the Author

Alexander Kozlovskiy
Software Developer (Senior)
Ukraine Ukraine
.net developer

Comments and Discussions

GeneralMy vote of 5 Pin
Member 151821421-Sep-17 19:36
MemberMember 151821421-Sep-17 19:36 
QuestionCan you show how to append nested objects to formsData? Pin
Member 1192641222-Aug-16 5:21
MemberMember 1192641222-Aug-16 5:21 
AnswerRe: Can you show how to append nested objects to formsData? Pin
Alexander Kozlovskiy22-Aug-16 7:29
MemberAlexander Kozlovskiy22-Aug-16 7:29 
GeneralRe: Can you show how to append nested objects to formsData? Pin
Member 1192641222-Aug-16 21:51
MemberMember 1192641222-Aug-16 21:51 
QuestionUsing it with AngularJS Pin
Member 1131820029-May-15 2:33
MemberMember 1131820029-May-15 2:33 
AnswerRe: Using it with AngularJS Pin
Alexander Kozlovskiy29-May-15 5:25
MemberAlexander Kozlovskiy29-May-15 5:25 
GeneralRe: Using it with AngularJS Pin
Member 1131820029-May-15 5:50
MemberMember 1131820029-May-15 5:50 
SuggestionMultiple File Upload Supported Now! Pin
Jener Garcia Menezes6-May-15 5:54
MemberJener Garcia Menezes6-May-15 5:54 
GeneralRe: Multiple File Upload Supported Now! Pin
Alexander Kozlovskiy7-May-15 5:23
MemberAlexander Kozlovskiy7-May-15 5:23 
QuestionThanks Pin
Valdis Iljuconoks10-Mar-15 23:57
MemberValdis Iljuconoks10-Mar-15 23:57 
AnswerRe: Thanks Pin
Alexander Kozlovskiy24-Mar-15 0:57
MemberAlexander Kozlovskiy24-Mar-15 0:57 
QuestionformData empty Pin
Member 1101580615-Aug-14 19:50
MemberMember 1101580615-Aug-14 19:50 
AnswerRe: formData empty Pin
Alexander Kozlovskiy15-Aug-14 20:50
MemberAlexander Kozlovskiy15-Aug-14 20:50 
GeneralRe: formData empty Pin
Member 1101580618-Aug-14 4:49
MemberMember 1101580618-Aug-14 4:49 
GeneralRe: formData empty Pin
Alexander Kozlovskiy18-Aug-14 8:12
MemberAlexander Kozlovskiy18-Aug-14 8:12 
QuestionNuGet Pin
Rory Primrose8-May-14 14:12
MemberRory Primrose8-May-14 14:12 
AnswerRe: NuGet Pin
Alexander Kozlovskiy8-May-14 22:30
MemberAlexander Kozlovskiy8-May-14 22:30 
GeneralMy vote of 5 Pin
Volynsky Alex4-Apr-14 12:34
professionalVolynsky Alex4-Apr-14 12:34 
GeneralRe: My vote of 5 Pin
Alexander Kozlovskiy5-Apr-14 0:29
MemberAlexander Kozlovskiy5-Apr-14 0:29 
GeneralRe: My vote of 5 Pin
Volynsky Alex5-Apr-14 2:55
professionalVolynsky Alex5-Apr-14 2:55 
SuggestionUse MimeMultipartContent Pin
rongchaua1-Mar-14 19:52
Memberrongchaua1-Mar-14 19:52 
GeneralRe: Use MimeMultipartContent Pin
mrwizzard5-Jun-14 12:30
Membermrwizzard5-Jun-14 12:30 
SuggestionExcellent! Pin
Axel Zarate4-Feb-14 8:33
MemberAxel Zarate4-Feb-14 8:33 
GeneralRe: Excellent! Pin
Alexander Kozlovskiy1-Apr-14 4:01
MemberAlexander Kozlovskiy1-Apr-14 4:01 

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