ASP.NET WebApi MultipartDataMediaFormatter

This is 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 (deep nested classes supported)
• all simple types that can be converted from/to string (using TypeConverter)
• files (MultipartDataMediaFormatter.Infrastructure.HttpFile class)
• 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 hosted on IIS (on Application Start):

GlobalConfiguration.Configuration.Formatters.Add(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;
    Assert.Fail(err);
  }
  
  var resultModel = response.Content.ReadAsAsync<ApiResult<T>>(new[] { mediaTypeFormatter }).Result;
  return resultModel;
  }
}

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

[HttpPost]
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
[HttpPost]
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
*/

History

Version 2.1.0 (2021-02-14)

• add support of netstandard2.0
• use Microsoft.Owin.Testing.TestServer instead of System.Web.Http.SelfHost.HttpSelfHostServer in test project to avoid running Visual Studio under administrator rights (for correct test completion)

Version 2.0.3 (2020-05-29)

• permit zero byte / empty files; allow file mediaType to be null

Version 2.0.2 (2018-06-09)

• signed the project with a strong name (without password) to allow referencing this project in projects that were signed with a strong name

Version 2.0.1 (2018-02-14)

• added possibility of using IEnumerable<> and IDictionary<,> as types for model's properties, for example: public IEnumerable<PersonModel> Persons {get;set;}

Version 2.0.0 (2017-05-27)

• added Nuget package MultipartDataMediaFormatter.V2

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 array if model has such property
• added class MultipartDataMediaFormatter.Infrastructure.MultipartFormatterSettings to control:
  • CultureInfo
  • serializing byte array as HttpFile when sending data
  • validating non nullable value types properties if there is 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 ) 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

License

Licensed under the MIT License.