How to access multi dimensional array in web API ..... Using angular and webapi

i am trying to upload an excel file and displaying the excel values in a html table. After that I will click on a button click- which will transfer the control to webapi with the values in the html table
I am using Angular and .net webapi 
So i have written a service as follows
i am trying to upload an excel file and displaying the excel values in a table.
So i have written a service as follows

import { Injectable } from '@angular/core';
import { HttpHeaders } from '@angular/common/http';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';



@Injectable({
  providedIn: 'root'
})
export class UploadServiceService {

  constructor(private http: HttpClient) { }
  
    url = 'http://localhost:xxxx/api/xyz/ExcelUpload'
    
  UploadExcel(formData: FormData) {
    let headers1 = new HttpHeaders();

    headers1.append('Content-Type', 'multipart/form-data');
    headers1.append('Accept', 'application/json');

    const httpOptions = { headers: headers1 };

    return this.http.post(this.url , formData, httpOptions)  
  }

}

Next I have called the service in component.ts which is as follows
getApprovals()
  {
    alert("from getapprovals");
    let formData = new FormData()
    formData.append('upload', this.arrayDisplay)
        this.service.UploadExcel(formData).subscribe(result => {
        this.message = result.toString();      
        });
    
  }
Next I am trying to access the values of the array in webapi in the following way.

if (HttpContext.Current.Request.TotalBytes > 0)
            {
                foreach (string key in HttpContext.Current.Request.Form.AllKeys)
                {
                    string value = HttpContext.Current.Request.Form[key];

                
                }
            }

But I am getting the value of HttpContext.Current.Request.Form[key] as 
"[object Object],[object Object],[object Object],[object Object]"
Actually in the array I have 4 records…. Each record has multiple values internally. 

How can I resolve this. Please help me

string message ="";
           var jsonString = String.Empty;

           HttpContext.Current.Request.InputStream.Position = 0;

           //using (var inputStream = new StreamReader(HttpContext.Current.Request.InputStream))
           //{
           //    jsonString = inputStream.ReadToEnd();
           //}


           var dictionary = new Dictionary<string, object>();
           HttpContext.Current.Request.Form.CopyTo(dictionary);

           if (HttpContext.Current.Request.TotalBytes > 0)
           {
               foreach (string key in HttpContext.Current.Request.Form.AllKeys)
               {
                   string value = HttpContext.Current.Request.Form[key];


               }
           }