我已经完成了以下工作:

I have done the job as follow:

.net core 2.0 Web API

at .Net core 2.0 web api

使用Microsoft.AspNetCore.Http;

using Microsoft.AspNetCore.Http;

我创建了一个模型类

namespace Marter_MRM.Models
{
    public class FileUploadViewModel
    {
        public IFormFile File { get; set; }
        public string source { get; set; }
        public long Size { get; set; }
        public int Width { get; set; }
        public int Height { get; set; }
        public string Extension { get; set; }
    }
}

然后我创建了一个控制器类，并按如下所示编写了函数.

And then I created a controller class and wrote the function as follow.

[HttpPost]
[Route("upload")]
public async Task<IActionResult> Upload(FileUploadViewModel model) {
      var file = model.File;

      if (file.Length > 0) {
           string path = Path.Combine(_env.WebRootPath, "uploadFiles");
           using (var fs = new FileStream(Path.Combine(path, file.FileName), FileMode.Create))
           {
                await file.CopyToAsync(fs);
           }

           model.source = $"/uploadFiles{file.FileName}";
           model.Extension = Path.GetExtension(file.FileName).Substring(1);
      }
    return BadRequest();
}

并在react中编写api调用函数，如下所示:

And write api call function in react as follow:

handleUploadClick(event){
    event.preventDefault();
    var self = this;
    var apiBaseUrl =  axios.defaults.baseURL + "user/upload";
    if(this.state.filesToBeSent.length>0){
        var filesArray = this.state.filesToBeSent;
        let f = new FormData();
        for(var i in filesArray){
        //console.log("files",filesArray[i][0]);
             f = new FormData();
             f.append("File",filesArray[i][0] )
             axios.post(apiBaseUrl, f, {
                    headers: {'Content-Type': 'multipart/form-data'}
             });
        }
        alert("File upload completed");
    }
    else{
        alert("Please select files first");
    }
}

效果完美.谢谢！