Program.cs

var builder = WebApplication.CreateBuilder(args);

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

// Add CORS policy
builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowAll",
        builder =>
        {
            builder
                .AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader()
                .WithExposedHeaders("Access-Control-Allow-Origin");
        });
});

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseHsts();
}

// Add CORS middleware
app.UseCors("AllowAll");

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

app.MapControllerRoute(
    name: "default",
    pattern: "{controller}/{action=Index}/{id?}");

app.MapFallbackToFile("index.html");

app.Run();