How to consume Oauth2.0 REST API into ASP.NET Core MVC

Hello Manish,

Please find below links that will help you out.

https://www.c-sharpcorner.com/article/asp-net-mvc-oauth-2-0-rest-web-api-authorization-using-database-first-approach/

https://www.c-sharpcorner.com/UploadFile/8a67c0/database-first-approach-with-Asp-Net-mvc-step-by-step-part-1/

Program.cs 

using Microsoft.Identity.Client;

var builder = WebApplication.CreateBuilder(args);

// ... other configurations

builder.Services.AddAuthentication(Microsoft.AspNetCore.Authentication.OpenIdConnect.OpenIdConnectDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApp(builder.Configuration.GetSection("AzureAd"));

builder.Services.AddAuthorization();

var app = builder.Build();

// ... other configurations

app.UseAuthentication();
app.UseAuthorization();

appsettings.json (this is just an example use any key-pair as per your API)

{
  "AzureAd": {
    "Instance": "https://login.microsoftonline.com/",
    "Domain": "yourtenant.onmicrosoft.com",
    "ClientId": "your-client-id",
    "ClientSecret": "your-client-secret",
    "TenantId": "your-tenant-id",
    "CallbackPath": "/signin-oidc"
  }
}

public class YourController : Controller
{
    private readonly IConfidentialClientApplication _confidentialClientApp;
    private readonly IHttpClientFactory _httpClientFactory;

    public YourController(IConfidentialClientApplication confidentialClientApp, IHttpClientFactory httpClientFactory)
    {
        _confidentialClientApp = confidentialClientApp;
        _httpClientFactory = httpClientFactory;
    }

    public async Task Index()
    {
        var result = await _confidentialClientApp.AcquireTokenForClient(new[] { "your-api-scope" })
            .ExecuteAsync();

        var accessToken = result.AccessToken;

        using var client = _httpClientFactory.CreateClient();
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);

        // Make your API request using client
        // Example:
        var response = await client.GetAsync("https://api.example.com/data");
        // Process the response

        return View();
    }
}