L'API Web: comment accéder à multipart les valeurs d'un formulaire lors de l'utilisation de MultipartMemoryStreamProvider?

Mis à jour 4/28/2015

Vous pouvez créer un fournisseur personnalisé basé sur MultipartFormDataRemoteStreamProvider.

Exemple:

public class CustomMultipartFormDataProvider : MultipartFormDataRemoteStreamProvider
{
    public override RemoteStreamInfo GetRemoteStream(HttpContent parent, HttpContentHeaders headers)
    {
        return new RemoteStreamInfo(
            remoteStream: new MemoryStream(),
            location: string.Empty,
            fileName: string.Empty);
    }
}

---

Mis à jour

Personnalisé En mémoire MultiaprtFormDataStreamProvider:

public class InMemoryMultipartFormDataStreamProvider : MultipartStreamProvider
{
private NameValueCollection _formData = new NameValueCollection();
private List<HttpContent> _fileContents = new List<HttpContent>();
//Set of indexes of which HttpContents we designate as form data
private Collection<bool> _isFormData = new Collection<bool>();
///<summary>
///Gets a <see cref="NameValueCollection"/> of form data passed as part of the multipart form data.
///</summary>
public NameValueCollection FormData
{
get { return _formData; }
}
///<summary>
///Gets list of <see cref="HttpContent"/>s which contain uploaded files as in-memory representation.
///</summary>
public List<HttpContent> Files
{
get { return _fileContents; }
}
public override Stream GetStream(HttpContent parent, HttpContentHeaders headers)
{
//For form data, Content-Disposition header is a requirement
ContentDispositionHeaderValue contentDisposition = headers.ContentDisposition;
if (contentDisposition != null)
{
//We will post process this as form data
_isFormData.Add(String.IsNullOrEmpty(contentDisposition.FileName));
return new MemoryStream();
}
//If no Content-Disposition header was present.
throw new InvalidOperationException(string.Format("Did not find required '{0}' header field in MIME multipart body part..", "Content-Disposition"));
}
///<summary>
///Read the non-file contents as form data.
///</summary>
///<returns></returns>
public override async Task ExecutePostProcessingAsync()
{
//Find instances of non-file HttpContents and read them asynchronously
//to get the string content and then add that as form data
for (int index = 0; index < Contents.Count; index++)
{
if (_isFormData[index])
{
HttpContent formContent = Contents[index];
//Extract name from Content-Disposition header. We know from earlier that the header is present.
ContentDispositionHeaderValue contentDisposition = formContent.Headers.ContentDisposition;
string formFieldName = UnquoteToken(contentDisposition.Name) ?? String.Empty;
//Read the contents as string data and add to form data
string formFieldValue = await formContent.ReadAsStringAsync();
FormData.Add(formFieldName, formFieldValue);
}
else
{
_fileContents.Add(Contents[index]);
}
}
}
///<summary>
///Remove bounding quotes on a token if present
///</summary>
///<param name="token">Token to unquote.</param>
///<returns>Unquoted token.</returns>
private static string UnquoteToken(string token)
{
if (String.IsNullOrWhiteSpace(token))
{
return token;
}
if (token.StartsWith("\"", StringComparison.Ordinal) && token.EndsWith("\"", StringComparison.Ordinal) && token.Length > 1)
{
return token.Substring(1, token.Length - 2);
}
return token;
}
}

Utilisation:

public async Task Post()
{
if (!Request.Content.IsMimeMultipartContent("form-data"))
{
throw new HttpResponseException(HttpStatusCode.BadRequest);
}
var provider = await Request.Content.ReadAsMultipartAsync<InMemoryMultipartFormDataStreamProvider>(new InMemoryMultipartFormDataStreamProvider());
//access form data
NameValueCollection formData = provider.FormData;
//access files
IList<HttpContent> files = provider.Files;
//Example: reading a file's stream like below
HttpContent file1 = files[0];
Stream file1Stream = await file1.ReadAsStreamAsync();
}