采用文件上传和附加参数的 WebAPI 方法 [英] WebAPI method that takes a file upload and additional arguments

问题描述

我想上传一个文件并随文件一起发送一些附加信息，比如一个字符串 foo 和一个 int bar.

I want to upload a file and send along with the file some additional information, let's say a string foo and an int bar.

我将如何编写接收文件上传、字符串和整数的 ASP.NET WebAPI 控制器方法?

我的 JavaScript:

My 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:

My WebAPI controller can access the file like this:

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

但我不清楚如何获得我的字符串和整数.我想我可能会说 streamProvider.Content[1] 或其他什么，但这感觉超级讨厌.

But it's not clear to me how I can get at my string and my int. I figure I can probably say streamProvider.Content[1], or whatever, but that feels super nasty.

编写接受文件上传、字符串和整数的 WebAPI 操作的正确方法是什么?

What's the Right Way© to write a WebAPI action that accepts a file upload, a string, and an int?

推荐答案

您可以创建自己的 MultipartFileStreamProvider 以访问附加参数.

You can create your own MultipartFileStreamProvider to access the additional arguments.

在 ExecutePostProcessingAsync 中，我们以多部分形式遍历每个文件并加载自定义数据(如果您只有一个文件，则 CustomData 中只有一个对象> 列表).

In ExecutePostProcessingAsync we loop through each file in multi-part form and load the custom data (if you only have one file you'll just have one object in the CustomData list).

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;
    }
}

然后在您的控制器中:

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);
    }
}

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