advsellorben got the answer before I did. If you need these exact URLs and those exact methods, this is the only way. You can reduce the number of routes by combining GetUser and GetAllUsers in one action with a null identifier, for example.
routes.MapRoute( "GetUser", "users/{id}", new { controller = "Users", action = "GetUser", id = UrlParameter.Optional} new { id = @"\d+" }
To call the GetUser(int? id) method
If you want to use the URL to automatically start the controller and action, you will need something like
routes.MapRoute( "GetUser", "{controller}/{action}/{id}", new { id = UrlParameter.Optional} new { id = @"\d+" }
But for this you need to change the URLs you need so that /users/getuser/1234 GetUser(int id) to GetUser(int id) and /users/getallusers to GetAllUsers() . This is untested, by the way, there may be some minor errors.
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