Question

我有一个Controller，它使用表单数据接受IFormFile和对象（称为Document的类）。

这是控制器：

[HttpPost]
public async Task<IActionResult> Post(IFormFile file, [FromForm] Document document, CancellationToken token = default)
{
    ...
}

Document类的外观如下：

public class Document
{
    public Guid DocumentId { get; set; }
    public string Name { get; set; }
    public DocumentType DocumentType { get; set; } = DocumentType.Unsorted;
    public Dictionary<string, string> Metadata { get; set; } = new Dictionary<string, string>();
}

这是POST的数据发送到所述控制器的代码：

using (var multipartContent = new MultipartFormDataContent())
{
    multipartContent.Add(new StringContent(document.DocumentId.ToString()), FormDataKeys.DocumentId);
    multipartContent.Add(new StringContent(document.DocumentType.ToString()), FormDataKeys.DocumentType);
    multipartContent.Add(new StreamContent(file), FormDataKeys.File, document.Name);

    using (var apiResult = await _httpClient.PostAsync("api/documents", multipartContent, token))
    {
        var content = await apiResult.Content.ReadAsStringAsync();
        return JsonConvert.DeserializeObject<StoreDocumentResult>(content);
    }
}

此方法有效，当我发送POST请求时，控制器中的IFormFile和[FromForm] Document参数的属性都被填写。只是，我对如何填充Metadata的{{1}}属性一无所知？如何在Document中传递Dictionary<string, string>？

Answer 1

最简单的方法是使用JSON将字典序列化为字符串，然后反序列化。

     var settings = new JsonSerializerSettings();
    settings.Formatting = Formatting.Indented;
    settings.ContractResolver = new DictionaryAsArrayResolver();

    // serialize
    string json = JsonConvert.SerializeObject(Document.Metadata, settings);

和

   multipartContent.Add(new StringContent(json ), FormDataKeys.Metadata );

要反序列化它，您可以使用如下代码：

var d  = JsonConvert.DeserializeObject<Dictionary<String,String>>(json, settings);

另一个选择是子类化HttpContent并重写SerializeToStreamAsync方法。在这种情况下，您可以根据需要将其写入提供的缓冲区。

class DictionaryContent: HttpContent
{
   public Object Value { get; }

   public DictionaryContent( Object value)
   {
       Value = value;
       Headers.ContentType = .. You must provide the desired content type.
   }

   protected override Task SerializeToStreamAsync( Stream stream, TransportContext context )
   {
        using ( var buffer = new BufferStreamWriter( stream, 4096 ) )
        {
            var writer = new JsonWriter( buffer, JsonSettings.Default );
            writer.WriteValue( Value ); // HERE You can do anything that you want.
        }

        return Task.CompletedTask;
   }
}

如何在MultipartFormData中传递字典？

1 个答案: