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.

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

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: {}
}

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

Adding a method to an object with TypeScript: A step-by-step guide

In my current scenario, I am faced with a challenge where I need to test a function with a specific use of this. However, typescript poses constraints by either disallowing me from adding the method to the object, or if I define it as any, then my interfac ...

What exactly does <T> signify within the realm of dynamic forms?

Currently, I am experimenting with the Angular2 cookbook instructions for Dynamic Forms. The instructions mention: export class QuestionBase<T>{ value: T, ... I am confused about the purpose of the "<T>" in both instances. Do you have any ins ...

Encountering issue while resolving flux/utils in webpack

My TypeScript OS project is in the process of being migrated to webpack, Unfortunately, I am currently facing a build error: ERROR in ./src/store/GigaStore.ts Module not found: Error: Cannot resolve module 'flux/utils' in /home/erfangc/GigaGrid ...

Guide to eliminating text following a space within a string in Angular 8

Having trouble trying to capitalize the first letter after an underscore in a string using Angular 8. Can anyone help me find a solution? app.component.ts: let content="power_managment 0vol"; alert(content.split( ).[0]); // desired output: "powerManagmen ...

Prevent the element attribute from being enabled before the onclick function is triggered

I am attempting to implement a feature in Angular that prevents double clicking on buttons using directives. Below is the pertinent code snippet from my template: <button (click)="onClickFunction()" appPreventDoubleClick>Add</button> And her ...

In a standalone script, the error message "ReferenceError: exports is not defined in ES module scope" is encountered

When I execute the script using npx ts-node -i --esm --skipProject -T .\seed.ts import { readdir, readFile } from "node:fs/promises" async function readFeedsFromFiles() { const data = await readdir("./seedData/feeds", { ...

Creating a list of components for drag and drop with Angular CDK is a straightforward process that involves following

I am attempting to use Angular's CDK drag and drop functionality to create a list of components that can be rearranged. However, I am encountering an issue where the components are not being displayed correctly. In my App.component.ts file: impo ...

Guide on creating a static method to generate a subclass instance

I am currently working on creating an abstract class called Enum, which consists of static methods that return instances of the class they are invoked upon. However, I am encountering difficulties in properly typing these methods. My goal is to help TypeS ...

Can you suggest ways to reduce the size of a Docker Image for better optimization?

I have an Angular application running locally on V10. I am attempting to create a Docker image using a Dockerfile. However, during the image creation process, my Docker image size is becoming very large at 1.32GB. Is there any method to decrease its size? ...

Troubles with converting CSS from left-to-right (LTR) to right-to-left (RTL) in

I am currently working on an Angular2 application and utilizing npm scripts and Webpack2 for my AOT builds as well as creating language specific bundles. In my Arabic configuration file, I attempted to implement the following code snippet: { test: /\ ...

Angular 8 ngBootstrap - Resizable and Draggable Modal Feature

Currently, I am attempting to integrate Bootstrap version 4 with Angular 8. My main goal is to create a modal that is both re-sizable and draggable. Although there are some examples available for other versions such as 3.xx, none seem to be specifically de ...

The Angular component seems to be lacking a template

During the upgrade process of my Angular 8 app to Angular 9, I encountered an error message while trying to build: ERROR in component is missing a template The issue is that it doesn't specify which specific component is missing a template. Is there ...

This TypeScript error occurs when the props are not compatible and cannot be assigned to

Hello fellow Internet dwellers! I am a novice in the world of coding and TypeScript, seeking some assistance here. I am attempting to extract an array of objects from props, transform it into a new object with specific information, and then return it - ho ...

Sending various kinds of generic types to React component properties

Currently, my team and I are working on a TypeScript/React project that involves creating a versatile 'Wizard' component for multi-step processes. This Wizard acts as a container, receiving an array of 'panel' component properties and p ...

Troubleshooting TypeScript when importing external JavaScript: Module not found or no type declaration file available

I recently acquired a VueJS admin template built in JS and am looking to integrate it into my existing TS application. However, when I attempt to transfer the components, views, and other elements, I encounter the following error message. Is there a way to ...

The process of removing and appending a child element using WebDriverIO

I am trying to use browser.execute in WebDriverIO to remove a child element from a parent element and then append it back later. However, I keep receiving the error message "stale element reference: stale element not found". It is puzzling because keepin ...

Utilizing Async Storage for Language Localization

Currently, I am utilizing two separate APIs for localization, both of which return JSON data. getEnLoc() //400kb getEsLoc() //400kb My plan is to call these APIs in App.ts during the app's initialization phase and store the retrieved JSON objects in ...

Generate a list of items in typescript, and then import them into a react component dynamically

I have a variable that stores key/value pairs of names and components in a TypeScript file. // icons.tsx import { BirdIcon, CatIcon } from 'components/Icons'; interface IconMap { [key: string]: string | undefined; } export const Icons: IconM ...

Maintain Angular Dropdown Menu Open Across Page Refresh

I am currently working on an HTML/Typescript view that is connected to a SQL Database. Whenever there are changes made to the database, the entire webpage reloads. The issue we are facing is that we have dropdown menus on the page that clients want to rema ...

Can Observable subscriptions in Angular be tested?

I'm a newcomer to angular and I'm currently working on creating unit tests for the function below. HomeComponent.ts ngOnInit() { this.msalBroadcastService.inProgress$ .pipe( filter((status: InteractionStatus) => status === ...