我如何将对象从 Angular 发送到 Asp.net Web Api？

Question

我的网站出现异常 Api

Object reference not set to an instance of an object.

对象中的数据打印到控制台，但未传递到 Api 控制器。对象 ae s "null"

这是我的控制器：

[Route("api/AddMovie")]
[HttpPost]
public int AddMovie([FromBody]Movie movie)
{
   int check = objMovie.AddMovie(movie);
   return check;
}

AddMovie 是我创建的用于在数据库中存储数据的函数。

这是我的组件：

import { FormGroup, FormControl, Validators, FormBuilder } from '@angular/forms';
import { slideInOutAnimation } from 'src/app/animations';
import { Movie } from 'src/app/movie';
import { NgxSpinnerService} from 'ngx-spinner';
import { MovieServiceService } from 'src/app/Service/movie-service.service';
import { HttpClient } from '@angular/common/http';
import { formatNumber } from '@angular/common';

@Component({
  selector: 'app-addmovie',
  templateUrl: './addmovie.component.html',
  styleUrls: ['./addmovie.component.css'],
  // make slide in/out animation available to this component
  animations: [slideInOutAnimation],

  // attach the slide in/out animation to the host (root) element of this component
  // tslint:disable-next-line: no-host-metadata-property
  host: { '[@slideInOutAnimation]': '' }
})
export class AddmovieComponent implements OnInit {

  // tslint:disable-next-line: new-parens
  movie = new Movie;
  fileData: File = null;
  addMovieForm: FormGroup;


  constructor( 
    private spinner: NgxSpinnerService,
    public fb: FormBuilder,
    private http: HttpClient,
    public movieService: MovieServiceService) {
    this.addMovieForm = this.fb.group ({
      movieName: new FormControl('', [Validators.required, Validators.minLength(1)]),
      releaseDate: new FormControl('', [Validators.required]),
      releaseYear: new FormControl('' , [Validators.required]),
      certification: new FormControl('' , [Validators.required]),
      runtime: new FormControl('', [Validators.required]),
      rating: new FormControl('', [Validators.required, Validators.max(10)]),
      moviePlot: new FormControl('', [Validators.required, Validators.minLength(1)]),
      cast: new FormControl('', [Validators.required, Validators.minLength(1)]),
      imageName: new FormControl('', [Validators.required])
    });
  }

  ngOnInit() {
  }

  onFileSelect(event) {
    if (event.target.files.length > 0) {
      const file = event.target.files[0];
      this.addMovieForm.get('imageName').setValue(file);
    }
  }
  public onSubmit() {
    debugger;
    // tslint:disable-next-line: prefer-const
    let movieForm = this.addMovieForm.value;
    this.movie.movieName = movieForm.movieName;
    this.movie.releaseDate = movieForm.releaseDate;
    this.movie.releaseYear = movieForm.releaseYear;
    this.movie.certification = movieForm.certification;
    this.movie.runtime = movieForm.runtime;
    this.movie.review = movieForm.rating;
    this.movie.moviePlot = movieForm.moviePlot;
    this.movie.cast = movieForm.cast;
    this.movie.imageName = movieForm.imageName;
    console.log(this.movie);
    this.http.post('http://localhost:50686/api/AddMovie', this.movie).subscribe(
      (res) => console.log(res),
      (err) => console.log(err)
    );
}
}

Answer 1

您正在调用 api 调用，但没有任何 header。尝试以下

const httpOptions = {
      headers: new HttpHeaders({
        'Content-Type': 'application/json'
      })
    };
this.http.post('http://localhost:50686/api/AddMovie', this.movie, httpOptions)
.subscribe(
      (res) => console.log(res),
      (err) => console.log(err)
    );

Answer 2

错误提示您的对象 Movie 为空。这意味着你还没有初始化你的对象，或者你已经将它设置为空。在这种情况下，您可以执行以下操作，

在使用之前初始化对象，
```
Movie movie = new Movie();
```

在使用对象实例之前检查是否为空，

public int AddMovie([FromBody]Movie movie)
{
    if (movie != null) {
        // Do something with movie
    }
}

处理 null 并抛出合适的异常，

public int AddMovie([FromBody]Movie movie)
{
    if (movie == null) {
        throw new Exception("Custom exception message");
    }
}

我如何将对象从 Angular 发送到 Asp.net Web Api？

How do i send an object from Angular to an Asp.net Web Api?

typescript

asp.net-web-api2

angular