how to post formdata or http.context.form data from angular 6 to asp.net mvc web api or api using Token based authentication with header

how to post formdata or http.context.form data from angular 6 to asp.net mvc web api or api using Token based authentication with header 

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Create form data :-

const formdata = new FormData();

    formdata.append('postJson', JSON.stringify(postJson));

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Attach Form data To Form-data object and call contract service to post data :-

this.PostService.Postdata(formdata).then((res: any) => {

      this.loggerService.info(res.status);

      this.responseStatus = res.status;

      this.responseDraftId = res.result.alfResponse.draftId;

      if (res.status === 200) {

        this.responseFilePath = res.result ? (res.result.FullFilePath ? res.result.FullFilePath : '') : '';

        this.showPopup('success', 'Success!', res.result.Reference + ' File has been created successfully.');

      } else {

        this.showPopup('error', 'Error!', 'Error while submit Contract!');

      }

    }).catch(error => {

      this.loggerService.error(error);

      this.showPopup('error', 'Error!', 'Error while submit Contract!');

    });

  }

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create Service "Post Service" with Promises :-

PostService(data: any): Promise<any> {

        return new Promise((resolve, reject) => {

            this.apiService.postWithformHeader('Contract/GenerateContract', data).subscribe((res: any) => {

                return resolve(res);

            }, (err) => {

                reject(err);

            });

        });

    }

//note apiservice is class name where this method is write

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method for form data header Attach with Token :-

postWithformHeader(URL, data) {

    this.spinner.displaySpinner(true);

    const optionsData: any;

if(localstorage.getkey('mytoken'))

{

optionsData = {

      headers: this.createAuthorizationHeader(),

    };

}

else{

this.router.navigate(['login']);

}

    const response = this.http.post(this.appUrl + URL, data,optionsData).map((res => {

      this.spinner.displaySpinner(false);

      return res;

    })).catch((error: any) => {

      this.spinner.displaySpinner(false);

      return this.httpErrorHandler.handleError('api-service', error, URL);

    });

    return response;

  }

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  Method for create header :- 

   createAuthorizationHeader() {

    

    let headers = new HttpHeaders();

      headers = headers.append('authorization', 'Bearer ' + localstorage.getkey('mytoken'));

   

     return headers;

  }

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