我正在嘗試上傳包含一些信息的照片。但堅持錯誤“'文件'類型的參數不能分配給'字符串'類型的參數?！蔽沂褂?angular 6 作為前端和后端，我使用 .net WebApi 和 SQL server 2012。在此先感謝大家，并希望盡快回復。圖片-upload.component.tsimageUrl:String="";fileToUpload:File=null;  handleImageChange(file: FileList){    this.fileToUpload = file.item(0);    var reader = new FileReader();    reader.onload=(event:any)=>{      this.imageUrl=event.target.result;    }    reader.readAsDataURL(this.fileToUpload);  } uploadImage(imageData){    let name=imageData.name;    let number=imageData.number;    let price=imageData.price;    this.service.uploadImage(name,this.fileToUpload,number,price).subscribe(      data=>{        alert("successfully uploaded");        this.productForm.reset();        this.imageUrl="";      }    );  }圖片-upload.service.ts uploadImage(fileToUpload:File, imagename:string, num:string, price:string){    let formData:FormData = new FormData();    formData.append("file",fileToUpload,fileToUpload.name);    formData.append("Imagename",imagename);    formData.append("Number",num);    formData.append("Price",price);    return this.http.post(this.baseUrl+"UploadImage",formData,this.httpOptions);    }錯誤：