Asp.net core default route

Question

Simplified Startup code:

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

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseMvc(routes =>
    {
        routes.MapRoute(
        name: "default",
        template: "",
        defaults: new { controller = "Main", action = "Index" });
    });
}

After running application in Visual Studio 2015 I see in browser "localhost:xxx", but I don't see result of MainController.Index(). Just blank page. What did I miss?

Update:

Web.config:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <system.webServer>
    <handlers>
      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified"/>
    </handlers>
    <aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false"/>
  </system.webServer>
</configuration>

Update 2:

The problem comes from exception in dependency injected service to controller and because I forget to use developer exception page site just returned blank page to me. So I'm sorry for incorrect question, but routing is fine in my case.

Answer 1

routes.MapRoute(
    name: "default",
    template: "{controller}/{action}/{id?}",
    defaults: new { controller = "Main", action = "Index" });

routes.MapRoute(
    name: "default",
    template: "{controller=Main}/{action=Index}/{id?}");

These are the two ways of defining default route. You are mixing them. You need always to define a template. In the second way you can write the defaults directly in the template.