When i'm posting binary data for images from angular 14 to Asp.Net 6 Rest Api, i just find image path & it's name but i lose binary data

Question

When i'm posting binary data for images from angular 14 to Asp.Net 6 Rest Api, i just find image path & it's name like that "C:\fakepath\2.jfif" but i lose binary data,How i can solve that problem. That's the service method by which i'm posting data to asp.net rest api

 postAdvertisement(adv: Advertisement): Observable<Advertisement> {

    return this.http.post<Advertisement>(this.baseApiUrl + '/api/advertisements',adv);
  }

Component

export class PostAdvComponent implements OnInit {

  advForm: FormGroup;
  @Input() adv: Advertisement;
  constructor(private fb: FormBuilder, private advService: AdvService) { }
  ngOnInit(): void {
    this.advForm = this.fb.group({
      id: [0],
      name: ['', Validators.required, Validators.minLength(1), Validators.maxLength(50)],
      price: ['', Validators.required],
      description: ['', Validators.required],
      images: this.fb.array([
        this.addImages()
      ])
    });
  }  
  addImages(): FormGroup {
    return this.fb.group({
      id: [0],
      contents: ['', Validators.required]
    })
  }

  uploadImage(event: any) {
    const files = event.target.files;
    for (let i = 0; i < files.length; i++) {
      const file = files[i];

      const reader = new FileReader();
      reader.readAsBinaryString(file); 

      //reader.readAsDataURL(file);
 
      reader.onload = (event) => {
        const uint8Array = new Uint8Array(event.target?.result as ArrayBuffer);
        
        const base64String  = Uint8Array.from(uint8Array).toString();
        //const jsonString = JSON.stringify({ data: base64String });
        this.advForm.patchValue({
          contents: base64String
        })
      }
    }

  addAdvertisement() {
    this.mapFormValuesToAdvModel();
    
    this.advService.postAdv(this.adv)
      .subscribe(add => {
        console.log(add);
      });
}
  mapFormValuesToAdvModel() {
    this.adv.name = this.advForm.value.name;
    this.adv.price = this.advForm.value.price;
    this.adv.description = this.advForm.value.description;
    this.adv.images = this.advForm.value.images;
  }
}

Html

 <div formArrayName="images">
                <div formGroupName="0">
                    <div class="form-group" [ngClass]="{'has-error' : formErrors.images}">
                        <div class="input-group">
                            <input type="file" id="photo" (change)="uploadImage($event)" formControlName="contents" name="photo"
                                class="form-control-file" (blur)="logValidationErrors()" multiple="multiple" />
                        </div>
                        <span class="help-block" *ngIf="formErrors.images">
                            {{formErrors.images}}
                        </span>
                    </div>
                </div>
            </div>

I'm expecting to get binary data into controller's model but i can't get it