how can I set a specific page as a default page in .net core 2 using visual studio code

Within that AddRazorPagesOptions() method, we can set things like route conventions and the root directory for pages. It turns out that, to set a default route for a page, you execute this call

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc().AddRazorPagesOptions(options =>
    {
        options.Conventions.AddPageRoute("/Account/Login", "");
    });
}

Check the Detailed post here https://exceptionnotfound.net/setting-a-custom-default-page-in-asp-net-core-razor-pages/

OR set default route in Startup.cs (https://andrewlock.net/exploring-program-and-startup-in-asp-net-core-2-preview1-2/)

   public IConfigurationRoot Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        // Add framework services.
        services.AddMvc();
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        //some code here
         
        //add routing here
        app.UseMvc(routes =>
        {
            //default route
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });
    }

In the above code we are adding a default route.

Thanks so much  vikas_jk.