接受文件上传和附加参数的 WebAPI 方法

Question

我想上传一个文件并随文件一起发送一些附加信息，比如说一个字符串 foo 和一个 int bar。

如何编写接收文件上传、字符串和 int 的 ASP.NET WebAPI 控制器方法？

我的 JavaScript：

var fileInput = document.querySelector("#filePicker");
var formData = new FormData();
formData.append("file", fileInput.files[0]);
formData.append("foo", "hello world!");
formData.append("bar", 42);

var options = {
   url: "/api/foo/upload",
   data: formData,
   processData: false // Prevents JQuery from transforming the data into a query string
};
$.ajax(options);

我的 WebAPI 控制器可以像这样访问文件：

public async Task<HttpResponseMessage> Upload()
{
    var streamProvider = new MultipartMemoryStreamProvider();
    await Request.Content.ReadAsMultipartAsync(streamProvider);
    var fileStream = await streamProvider.Contents[0].ReadAsStreamAsync();
}

但我不清楚如何获取字符串和 int。我想我可能会说 streamProvider.Content[1] 或其他什么，但这感觉超级讨厌。

编写接受文件上传、字符串和 int 的 WebAPI 操作的正确方法是什么？

Answer 1

您可以创建自己的MultipartFileStreamProvider 来访问其他参数。

在ExecutePostProcessingAsync 中，我们以多部分形式循环遍历每个文件并加载自定义数据（如果您只有一个文件，那么CustomData 列表中将只有一个对象）。

class MyCustomData
{
    public int Foo { get; set; }
    public string Bar { get; set; }
}

class CustomMultipartFileStreamProvider : MultipartMemoryStreamProvider
{
    public List<MyCustomData> CustomData { get; set; }

    public CustomMultipartFileStreamProvider()
    {
        CustomData = new List<MyCustomData>();
    }

    public override Task ExecutePostProcessingAsync()
    {
        foreach (var file in Contents)
        {
            var parameters = file.Headers.ContentDisposition.Parameters;
            var data = new MyCustomData
            {
                Foo = int.Parse(GetNameHeaderValue(parameters, "Foo")),
                Bar = GetNameHeaderValue(parameters, "Bar"),
            };

            CustomData.Add(data);
        }

        return base.ExecutePostProcessingAsync();
    }

    private static string GetNameHeaderValue(ICollection<NameValueHeaderValue> headerValues, string name)
    {
        var nameValueHeader = headerValues.FirstOrDefault(
            x => x.Name.Equals(name, StringComparison.OrdinalIgnoreCase));

        return nameValueHeader != null ? nameValueHeader.Value : null;
    }
}

然后在你的控制器中：

class UploadController : ApiController
{
    public async Task<HttpResponseMessage> Upload()
    {
        var streamProvider = new CustomMultipartFileStreamProvider();
        await Request.Content.ReadAsMultipartAsync(streamProvider);

        var fileStream = await streamProvider.Contents[0].ReadAsStreamAsync();
        var customData = streamProvider.CustomData;

        return Request.CreateResponse(HttpStatusCode.Created);
    }
}

Answer 2

我认为这里的答案非常好。因此，其他人可以看到一个简单的示例，说明如何以摘要形式传递除了文件之外的数据，其中包括一个 Javascript 函数，该函数使 WebAPI 调用 FileUpload 控制器，以及来自 FileUpload 控制器的 sn-p（在 VB. net) 读取从 Javascript 传递的附加数据。

Javascript：

            function uploadImage(files) {
            var data = new FormData();
            if (files.length > 0) {
                data.append("UploadedImage", files[0]);
                data.append("Source", "1")
                var ajaxRequest = $.ajax({
                    type: "POST",
                    url: "/api/fileupload/uploadfile",
                    contentType: false,
                    processData: false,
                    data: data
                });

文件上传控制器：

        <HttpPost> _
    Public Function UploadFile() As KeyValuePair(Of Boolean, String)
        Try
            If HttpContext.Current.Request.Files.AllKeys.Any() Then
                Dim httpPostedFile = HttpContext.Current.Request.Files("UploadedImage")
                Dim source = HttpContext.Current.Request.Form("Source").ToString()

所以在Javascript中可以看到，传递的附加数据是“Source”键，值是“1”。正如 Chandrika 上面回答的那样，控制器通过“System.Web.HttpContext.Current.Request.Form("Source").ToString()”读取这个传递的数据。

请注意，Form("Source") 使用 ()（与 []）作为控制器代码在 VB.net 中。

希望这会有所帮助。

Answer 3

您可以通过这种方式提取多个文件和多个属性：

public async Task<HttpResponseMessage> Post()
{
    Dictionary<string,string> attributes = new Dictionary<string, string>();
    Dictionary<string, byte[]> files = new Dictionary<string, byte[]>();

    var provider = new MultipartMemoryStreamProvider();
    await Request.Content.ReadAsMultipartAsync(provider);
    foreach (var file in provider.Contents)
    {
        if (file.Headers.ContentDisposition.FileName != null)
        {
            var filename = file.Headers.ContentDisposition.FileName.Trim('\"');
            var buffer = await file.ReadAsByteArrayAsync();
            files.Add(filename, buffer);
        } else
        {
            foreach(NameValueHeaderValue p in file.Headers.ContentDisposition.Parameters)
            {
                string name = p.Value;
                if (name.StartsWith("\"") && name.EndsWith("\"")) name = name.Substring(1, name.Length - 2);
                string value = await file.ReadAsStringAsync();
                attributes.Add(name, value);
            }
        }
    }
    //Your code here  
    return new HttpResponseMessage(HttpStatusCode.OK);
}

Answer 4

var receipents = HttpContext.Current.Request.Params["Receipents"]; var 参与者 = HttpContext.Current.Request.Params["Participants"];

        var file = HttpContext.Current.Request.Files.Count > 0 ?  HttpContext.Current.Request.Files[0] : null;

        if (file != null && file.ContentLength > 0)
        {
            var fileName = Path.GetFileName(file.FileName);

            var path = Path.Combine(
                HttpContext.Current.Server.MapPath("~/uploads"),
                fileName
            );

            file.SaveAs(path);
        }

Answer 5

您可以通过以下方式做到这一点： jQuery 方法：

    var data = new FormData();

    data.append("file", filesToUpload[0].rawFile);
    var doc = {};            
    doc.DocumentId = 0; 
    $.support.cors = true;
    $.ajax({
        url: '/api/document/uploaddocument',
        type: 'POST',
        contentType: 'multipart/form-data',
        data: data,
        cache: false,
        contentType: false,
        processData: false,
        success: function (response) {
            docId = response.split('|')[0];
            doc.DocumentId = docId;
            $.post('/api/document/metadata', doc)
                .done(function (response) {
                });
          alert('Document save successfully!');
        },
        error: function (e) {
            alert(e);
        }
    });

调用您的“UploadDocuement”网络 API

[Route("api/document/uploaddocument"), HttpPost]
[UnhandledExceptionFilter]
[ActionName("UploadDocument")]
public Task<HttpResponseMessage> UploadDocument()
{
    // Check if the request contains multipart/form-data.
    if (!Request.Content.IsMimeMultipartContent())
    {
        Task<HttpResponseMessage> mytask = new Task<HttpResponseMessage>(delegate()
        {
            return new HttpResponseMessage()
            {
                StatusCode = HttpStatusCode.BadRequest,
                Content = "In valid file & request content type!".ToStringContent()
            };
        });
        return mytask;
    }


    string root = HttpContext.Current.Server.MapPath("~/Documents");
    if (System.IO.Directory.Exists(root))
    {
        System.IO.Directory.CreateDirectory(root);
    }
    var provider = new MultipartFormDataStreamProvider(root);

    var task = Request.Content.ReadAsMultipartAsync(provider).
    ContinueWith<HttpResponseMessage>(o =>
    {
        if (o.IsFaulted || o.IsCanceled)
            throw new HttpResponseException(HttpStatusCode.InternalServerError);

        FileInfo finfo = new FileInfo(provider.FileData.First().LocalFileName);

        string guid = Guid.NewGuid().ToString();

        File.Move(finfo.FullName, Path.Combine(root, guid + "_" + provider.FileData.First().Headers.ContentDisposition.FileName.Replace("\"", "")));

        string sFileName = provider.FileData.First().Headers.ContentDisposition.FileName.Replace("\"", "");

        FileInfo FInfos = new FileInfo(Path.Combine(root, guid + "_" + provider.FileData.First().Headers.ContentDisposition.FileName.Replace("\"", "")));

        Document dbDoc = new Document()
        {
            DocumentID = 0                

        };

        context.DocumentRepository.Insert(dbDoc);
        context.Save();

        return new HttpResponseMessage()
        {
            Content = new StringContent(string.Format("{0}|File uploaded.", dbDoc.DocumentID))
        };
    }
    );
    return task;

}

通过以下方式调用您的元数据 Web api：

[Route("api/document/metadata"), HttpPost]
[ActionName("Metadata")]
public Task<HttpResponseMessage> Metadata(Document doc)
{
    int DocId = Convert.ToInt32(System.Web.HttpContext.Current.Request.Form["DocumentId"].ToString());
        
    Task<HttpResponseMessage> mytask = new Task<HttpResponseMessage>(delegate()
    {
        return new HttpResponseMessage()
        {
            Content = new StringContent("metadata updated")
        };
    });
    return mytask;
}