Can reach WebAPI from Postman but not Angular app

If you are facing the issue where you can reach your WebAPI from Postman but not from your Angular app, there could be a few potential causes for this problem. In this blog post, we will explore some possible solutions to help you troubleshoot and resolve this issue.

1. CORS (Cross-Origin Resource Sharing) Issue

One common reason for this problem is a CORS issue. CORS is a security mechanism implemented in web browsers to restrict cross-origin requests. To resolve this, you need to configure your server to allow cross-origin requests from your Angular app.

To enable CORS in your WebAPI, you can add the following code in your server’s startup configuration:

public void ConfigureServices(IServiceCollection services)
{
    services.AddCors(options =>
    {
        options.AddPolicy("AllowOrigin",
            builder => builder.AllowAnyOrigin()
                              .AllowAnyMethod()
                              .AllowAnyHeader());
    });

    // Other configuration code...
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Other configuration code...

    app.UseCors("AllowOrigin");

    // Other configuration code...
}

Make sure to replace the “AllowOrigin” policy name with your desired policy name. This configuration allows any origin, method, and header to access your WebAPI. For production environments, you should consider restricting the allowed origins to enhance security.

2. Incorrect API Endpoint

Another possible reason is that you might be using an incorrect API endpoint in your Angular app. Double-check the URL you are using to make the HTTP request and ensure it matches the correct API endpoint.

Here is an example of how to make an HTTP request in Angular:

import { HttpClient } from '@angular/common/http';

@Injectable()
export class YourService {
    constructor(private http: HttpClient) { }

    getData() {
        return this.http.get('https://your-api.com/api/data');
    }
}

Make sure to replace ‘https://your-api.com/api/data’ with the actual URL of your WebAPI endpoint.

3. Authentication and Authorization

If your WebAPI requires authentication or authorization, make sure you are including the necessary credentials or tokens in your Angular app’s HTTP requests. Check if your API expects any specific headers or authentication mechanisms and ensure they are correctly implemented in your Angular app.

Here is an example of how to include an authorization header in an HTTP request:

import { HttpClient, HttpHeaders } from '@angular/common/http';

@Injectable()
export class YourService {
    constructor(private http: HttpClient) { }

    getData() {
        const headers = new HttpHeaders().set('Authorization', 'Bearer your-token');

        return this.http.get('https://your-api.com/api/data', { headers });
    }
}

Replace ‘your-token’ with the actual authentication token required by your WebAPI.

By following these solutions, you should be able to resolve the issue of being able to reach your WebAPI from Postman but not from your Angular app. Remember to test your application thoroughly after implementing any changes to ensure everything is working as expected.

We hope this blog post helps you in troubleshooting and resolving this issue. If you have any further questions, feel free to leave a comment below.

Can reach WebAPI from Postman but not Angular app