What is the best method to retrieve HTTP headers from the backend and simultaneously send HTTP parameters to it in ASP.NET Core and Angular?

Question

What is the best method to retrieve HTTP headers from the backend and simultaneously send HTTP parameters to it in ASP.NET Core and Angular?

I am currently working with Angular 15 and ASP.NET Core 5. The backend retrieves paged items based on the parameters pageSize and pageIndex.

Once the action method receives the pageSize and pageIndex parameters, it sends both the paged items and the totalCount to the frontend.

Below is the corresponding code snippet:

[HttpGet("getPagedCommodities")]
public async Task<IActionResult> GetPagedCommodities([FromQuery] PagingParameters pagingParameters)
{
    try
    { 
        var commodities = await _repository.Commodity.GetAllCommoditiesAsync();
        var totalCount = commodities.Count();
                
        var pagedCommodities = await _repository.Commodity.GetPagedCommoditiesAsync(pagingParameters);
                
        Response.Headers.Add("X-Pagination", JsonConvert.SerializeObject(totalCount));                

        return Ok(pagedCommodities);
    }
    catch
    {
        return StatusCode(500, "Internal server error");
    }
}

Here is the method in the frontend responsible for fetching the paged items:

getPagedCommodities(pageSize: number, pageNumber: number): Observable<CommodityForList[]> {
    let params: HttpParams = new HttpParams();
    params = params.append('pageSize', pageSize);
    params = params.append('pageNumber', pageNumber);
    
    let httpOptions = {
      params: params
    };
    return this.http.get<CommodityForList[]>(this.baseUrl + '/getPagedCommodities/', httpOptions);
      
  }

Is there a way to retrieve the value of the totalCount HTTP header parameter sent from the server?

Thank you for your assistance.

angular typescript asp.net-core

Answer 1

Answer №1

How to Retrieve Header Parameters from an API Response

I successfully incorporated your code into my custom Angular/.NET project and managed to develop a functional solution:

Backend: Startup.cs

To avoid getting an undefined value, I made sure to include X-Pagination in the CORS policy. For more information on why this step is necessary, you can visit this link.

services.AddCors(options =>
{
    options.AddDefaultPolicy(builder =>
    {
        builder.AllowAnyHeader()
                .AllowAnyMethod()
                .AllowAnyOrigin()
                .WithExposedHeaders("X-Pagination"); // Added this line for proper header access
    });
});

Backend: Controller Method

In order to work with the header parameters, I had to modify the input parameters from

PagingParameters pagingParameters

to

[FromQuery] int pageSize, [FromQuery] int pageNumber

:

[HttpGet("getPagedCommodities")]
public async Task<IActionResult> GetPagedCommodities([FromQuery] int pageSize, [FromQuery] int pageNumber)
{
    try
    { 
        var commodities = await _repository.Commodity.GetAllCommoditiesAsync();
        var totalCount = commodities.Count();
                
        var pagedCommodities = await _repository.Commodity.GetPagedCommoditiesAsync(pagingParameters);
                
        Response.Headers.Add("X-Pagination", JsonConvert.SerializeObject(totalCount));                

        return Ok(pagedCommodities);
    }
    catch
    {
        return StatusCode(500, "Internal server error");
    }
}

Frontend: Service Method

By setting observe: 'response', you gain access to

HttpResponse<YourJsonObject>

. This allows you to retrieve header values using

response.headers.get("Header-Key")

.

I also adjusted the way in which I constructed the httpOptions (the second parameter of this.http.get).

getPagedCommodities(pageSize: number, pageNumber: number): Observable<{commodities: CommodityForList[]; totalCount: number}> {

    const params: HttpParams = new HttpParams()
                                .append('pageSize', pageSize)
                                .append('pageNumber', pageNumber);

    const url = `${this.baseUrl}/getPagedCommodities/`;

    return this.http.get<CommodityForList[]>(url, { observe: 'response', params })
        .pipe(
            map(response => {

            // Retrieve 'total count' from header:
            const totalCount = response?.headers?.get('X-Pagination');
            const parsedTotalCount = +(totalCount ?? 0);

            return { commodities: response?.body ?? [],
                     totalCount: parsedTotalCount };
            })
        );
}

I was able to successfully access the returned values by executing the following code:

this.getPagedCommodities(0, 1).subscribe(
    res => {
        console.log('Commodities Array:', res.commodities);
        console.log('Total Count:', res.totalCount);
    }
);

Answer 2

How to Retrieve Header Parameters from an API Response

I successfully incorporated your code into my custom Angular/.NET project and managed to develop a functional solution:

Backend: Startup.cs

To avoid getting an undefined value, I made sure to include X-Pagination in the CORS policy. For more information on why this step is necessary, you can visit this link.

services.AddCors(options =>
{
    options.AddDefaultPolicy(builder =>
    {
        builder.AllowAnyHeader()
                .AllowAnyMethod()
                .AllowAnyOrigin()
                .WithExposedHeaders("X-Pagination"); // Added this line for proper header access
    });
});

Backend: Controller Method

In order to work with the header parameters, I had to modify the input parameters from

PagingParameters pagingParameters

to

[FromQuery] int pageSize, [FromQuery] int pageNumber

:

[HttpGet("getPagedCommodities")]
public async Task<IActionResult> GetPagedCommodities([FromQuery] int pageSize, [FromQuery] int pageNumber)
{
    try
    { 
        var commodities = await _repository.Commodity.GetAllCommoditiesAsync();
        var totalCount = commodities.Count();
                
        var pagedCommodities = await _repository.Commodity.GetPagedCommoditiesAsync(pagingParameters);
                
        Response.Headers.Add("X-Pagination", JsonConvert.SerializeObject(totalCount));                

        return Ok(pagedCommodities);
    }
    catch
    {
        return StatusCode(500, "Internal server error");
    }
}

Frontend: Service Method

By setting observe: 'response', you gain access to

HttpResponse<YourJsonObject>

. This allows you to retrieve header values using

response.headers.get("Header-Key")

.

I also adjusted the way in which I constructed the httpOptions (the second parameter of this.http.get).

getPagedCommodities(pageSize: number, pageNumber: number): Observable<{commodities: CommodityForList[]; totalCount: number}> {

    const params: HttpParams = new HttpParams()
                                .append('pageSize', pageSize)
                                .append('pageNumber', pageNumber);

    const url = `${this.baseUrl}/getPagedCommodities/`;

    return this.http.get<CommodityForList[]>(url, { observe: 'response', params })
        .pipe(
            map(response => {

            // Retrieve 'total count' from header:
            const totalCount = response?.headers?.get('X-Pagination');
            const parsedTotalCount = +(totalCount ?? 0);

            return { commodities: response?.body ?? [],
                     totalCount: parsedTotalCount };
            })
        );
}

I was able to successfully access the returned values by executing the following code:

this.getPagedCommodities(0, 1).subscribe(
    res => {
        console.log('Commodities Array:', res.commodities);
        console.log('Total Count:', res.totalCount);
    }
);

Answer 3

Answer №2

If you include the parameter observe: 'response' in your http get request, you will be able to observe the entire response and not just the body content.

this.http.get(myUrl, {
  observe: 'response',
  params
}).subscribe(response => console.log(response))

Now, instead of only receiving the body data, you will have access to the complete response object containing both the headers and body:

{
  headers: {
    totalCount: 123
  },
  status: 200,
  body: {}
}

Answer 4

If you include the parameter observe: 'response' in your http get request, you will be able to observe the entire response and not just the body content.

this.http.get(myUrl, {
  observe: 'response',
  params
}).subscribe(response => console.log(response))

Now, instead of only receiving the body data, you will have access to the complete response object containing both the headers and body:

{
  headers: {
    totalCount: 123
  },
  status: 200,
  body: {}
}

What is the best method to retrieve HTTP headers from the backend and simultaneously send HTTP parameters to it in ASP.NET Core and Angular?

Answer №1

Answer №2

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