我无法使用 FormGroup Angular 6 发出发布请求

Question

我是 Angular 新手，我无法使用 formGroup 发出帖子请求。正在为我拥有的所有字段发送正文，但是由于以下错误，出现错误 400（错误请求）： {"status":"error","errors":{"message":"A second操作在前一个操作完成之前在此上下文上开始。这通常是由使用相同 DbContext 实例的不同线程引起的，但不能保证实例成员是线程安全的。这也可能是由在客户端上评估嵌套查询引起的，如果是这种情况，请重写查询以避免嵌套调用。"}}，我有点理解错误是什么，但我不明白我的代码有什么问题。提前致谢

register.model.ts

export class User{
    FirstName: string;
    LastName: string;
    UserName: string;
    Email: string;
    Password: string;
}

register.service.ts

RegisterUser(user: User){
return this.http.post('url', user);

}

register.component.html

<form [formGroup]="registerForm" (ngSubmit)="onSubmit()">

  <div class="form-group row">
    <label class="col-sm-3 col-form-label">First Name:</label>
    <div class="col-sm-3">
      <input type="text" formControlName="FirstName" class="form-control"
        placeholder="First Name" ngModel>
    </div>
  </div>
  <div class="form-group row">
    <label class="col-sm-3 col-form-label">Last Name:</label>
    <div class="col-sm-3">
      <input type="text" formControlName="LastName" class="form-control"
        id="LastName" placeholder="LastName" ngModel>
    </div>
  </div>
  <div class="form-group row">
    <label for="UserName" class="col-sm-3 col-form-label">Username:</label>
    <div class="col-sm-3">
      <input type="text" formControlName="UserName" class="form-control"
        placeholder="User Name" ngModel>
    </div>
  </div>
  <div class="form-group row">
    <label for="Email" class="col-sm-3 col-form-label">Email:</label>
    <div class="col-sm-3">
      <input type="email" formControlName="Email" class="form-control"
        placeholder="example@example.com" ngModel>
    </div>
  </div>

  <div class="form-group row">
    <label for="password" class="col-sm-3 col-form-label">Password:</label>
    <div class="col-sm-3">
      <input type="password" formControlName="Password"  class="form-control"
        placeholder="*********" ngModel>
    </div>
  </div>

  <br>

  <p class="text-center">Already have an account? <span>
      <button (click)="goToSignIn();" class="unstyled-button">Sign In.</button>
    </span></p>

  <button type="submit" class="button button4">Sign Up</button>
</form>

register.component.ts

export class RegisterComponent implements OnInit {

user: User;
registerForm: FormGroup;

constructor(private router: Router, private userService: RegisterService, private toastr: 
          ToastrService, private fb: FormBuilder) { }

ngOnInit() {
  this.registerForm = this.fb.group({
    FirstName: ['', Validators.required],
    LastName: ['', Validators.required],
    UserName: ['', Validators.required],
    Email: ['', Validators.required],
    Password: ['', Validators.required],
  })
}


onSubmit(){
  return this.userService.RegisterUser(this.registerForm.value).subscribe((data:any) => {
    this.toastr.success('User Registered Successfully');
  }, error => {
    this.toastr.error('Registeration Failed');
  })
}

}

Answer 1

这不是您遇到问题的 javascript 错误。这是来自实体框架的错误。

您的 DBContext 正被两个线程同时使用。可能是同一请求中的两个线程使用它。

检查您的 DBContext 是否由于某种原因未声明为静态。

您需要分享您的 api 代码，以便我们调试您的问题。

Answer 2

试试这样：

registerUser(user) : Observable<any> {
return this.http.post<any>('url', JSON.stringify(user), this.httpOptions).pipe(
    tap((user) => console.log(`user sent : ${JSON.stringify(user)}`)),
    catchError(this.handleError)
  );

};

httpOptions 是这样的：

httpOptions = {
headers: new HttpHeaders({
'Content-Type': 'application/json'
})

};

捕获错误：

handleError(error) {
let errorMessage = '';
if(error.error instanceof ErrorEvent) {
// Get client-side error
errorMessage = error.error.message;
} else {
// Get server-side error
errorMessage = `Error Code: ${error.status}\nMessage: ${error.message}`;
}
window.alert(errorMessage);
return throwError(errorMessage);
}