Example ASP.NET Core Razor Page in C# that calls a quotes REST API with fallback to offline quotes in case of failure

README.md

Index.cshtml

@page
@model IndexModel
@{
    ViewData["Title"] = "Home page";

    <div class="card">
        <div class="card-body">
            @await Model.GetInspirationalQuote()
        </div>
        <div class="card-footer">
            <form method="get">
                <button class="btn btn-primary btn-sm" type="submit">Get New Quote</button>
            </form>
        </div>
    </div>
}

<div class="text-center">
    <h1 class="display-4">Welcome</h1>
    <p>Learn about <a href="https://docs.microsoft.com/aspnet/core">building Web apps with ASP.NET Core</a>.</p>
</div>

Index.cshtml.cs

using System.Diagnostics;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace WebApplication108.Pages;
public class IndexModel : PageModel
{
    private readonly ILogger<IndexModel> _logger;
    private readonly HttpClient _httpClient;

    public IndexModel(ILogger<IndexModel> logger, IHttpClientFactory httpClientFactory)
    {
        _logger = logger;
        _httpClient = httpClientFactory.CreateClient("quotes.api");
    }

    public void OnGet()
    {

    }

    private static List<string> _backupQuotes = new()
    {
        "The determination to win is the better part of winning.",
        "if ( socialDistancing.isOver() ){\n\tpeople.hug();\n}",
        "await sign"
        // Add more backup quotes here
    };

    private static string GetBackupQuote()
    {
        var index = Random.Shared.Next(_backupQuotes.Count - 1);
        return _backupQuotes[index];
    }

    public async Task<string> GetInspirationalQuote()
    {
        const string apiPath = "quote";
        try
        {
            var sw = new Stopwatch();
            var quote = await _httpClient.GetFromJsonAsync<QuoteResult>(apiPath);
            sw.Stop();

            if (_logger.IsEnabled(LogLevel.Information))
            {
                _logger.LogInformation("Call to {url} took {apiResponseTime}", new Uri(_httpClient.BaseAddress!, apiPath), sw.Elapsed);
            }

            return quote?.Quote ?? GetBackupQuote();
        }
        catch (Exception ex)
        {
            // There was an error calling the API, fallback to offline/backup quotes
            if (_logger.IsEnabled(LogLevel.Error))
            {
                _logger.LogError(ex, "Error calling quote of the day API at {url}: {errorMessage}", new Uri(_httpClient.BaseAddress!, apiPath), ex.Message);
            }

            return GetBackupQuote();
        }
    }

    public class QuoteResult
    {
        public string? Quote { get; init; }
    }
}

Program.cs

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();

builder.Services.AddHttpClient("quotes.api", http =>
{
    // Get API key from appropriate place, e.g. user secrets in dev, environment variable in prod, etc.
    //var apiKey = builder.Configuration["QuotesApi:ApiKey"];
    //http.DefaultRequestHeaders.Add("X-API-Key", apiKey);
    // Add any other required headers

    // Set base address
    http.BaseAddress = new Uri("https://nodejs-quoteapp.herokuapp.com/");
});

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseRouting();

app.UseAuthorization();

app.MapRazorPages();

app.Run();