To add a global route prefix in ASP.NET Core 6, you can use the Route attribute at the application level. This allows you to specify a common route prefix for all the controllers and actions in your application. Here's how you can do it:

Open your Startup.cs file.

Inside the ConfigureServices method, add the following code to configure route options with a global route prefix:

services.AddControllers(options =>
{
    options.Conventions.Insert(0, new RoutePrefixConvention("prefix")); // Replace "prefix" with your desired route prefix
});

In the code above, replace "prefix" with the desired global route prefix you want to use.

1. Create a custom RoutePrefixConvention class to handle the route prefix. You can do this by adding the following code:

public class RoutePrefixConvention : IControllerModelConvention
{
    private readonly AttributeRouteModel _centralPrefix;

    public RoutePrefixConvention(string prefix)
    {
        _centralPrefix = new AttributeRouteModel(new RouteAttribute(prefix));
    }

    public void Apply(ControllerModel controller)
    {
        if (!controller.Selectors.Any())
        {
            return;
        }

        foreach (var selectorModel in controller.Selectors)
        {
            selectorModel.AttributeRouteModel = AttributeRouteModel.CombineAttributeRouteModel(_centralPrefix, selectorModel.AttributeRouteModel);
        }
    }
}

1. Now, you have set up a global route prefix for your controllers and actions. You can use the specified prefix for all your routes.

For example, if you have a controller named HomeController with an action named Index, and you've set the prefix to "myapp," the URL for the Index action will be https://yourdomain.com/myapp/Home/Index.

This approach allows you to define a global route prefix for your ASP.NET Core 6 application, making it easier to manage and organize your routes.