我们来看IRouteBuilder的定义：

public interface IRouteBuilder    {        IRouter DefaultHandler { get; set; }        IServiceProvider ServiceProvider { get; }        IList
     
       Routes { get; }        IRouter Build();    }
     

一个默认的IRouter对象，一个Build方法，一个IRouter集合和一个获取服务对象IServiceProvider。

我们进一步看IRouteBuilder的实现RouterBuilder:

public class RouteBuilder : IRouteBuilder    {        public RouteBuilder()        {            Routes = new List
      
       ();        }        public IRouter DefaultHandler { get; set; }        public IServiceProvider ServiceProvider { get; set; }        public IList
       
         Routes        {            get;            private set;        }        public IRouter Build()        {            var routeCollection = new RouteCollection();            foreach (var route in Routes)            {                routeCollection.Add(route);            }            return routeCollection;        }    }
       
      

主要的实现是Build方法，这个方法的实现也很简单，遍历Routes向一个实现了IRouter接口的RouteCollection对象添加IRouter,我们可以先看一下RouteCollection的实现：

public class RouteCollection : IRouteCollection    {        private readonly List
     
       _routes = new List
      
       ();        private readonly List
       
         _unnamedRoutes = new List
        
         ();        private readonly Dictionary
         
           _namedRoutes =                                    new Dictionary
          
           (StringComparer.OrdinalIgnoreCase); private RouteOptions _options; public IRouter this[int index] { get { return _routes[index]; } } public int Count { get { return _routes.Count; } } public void Add([NotNull] IRouter router) { var namedRouter = router as INamedRouter; if (namedRouter != null) { if (!string.IsNullOrEmpty(namedRouter.Name)) { _namedRoutes.Add(namedRouter.Name, namedRouter); } } else { _unnamedRoutes.Add(router); } _routes.Add(router); } public async virtual Task RouteAsync(RouteContext context) { for (var i = 0; i < Count; i++) { var route = this[i]; var oldRouteData = context.RouteData; var newRouteData = new RouteData(oldRouteData); newRouteData.Routers.Add(route); try { context.RouteData = newRouteData; await route.RouteAsync(context); if (context.IsHandled) { break; } } finally { if (!context.IsHandled) { context.RouteData = oldRouteData; } } } } public virtual VirtualPathData GetVirtualPath(VirtualPathContext context) { EnsureOptions(context.Context); // If we're using Best-Effort link generation then it means that we'll first look for a route where // the route values are validated (context.IsBound == true). If we can't find a match like that, then // we'll return the path from the first route to return one. var useBestEffort = _options.UseBestEffortLinkGeneration; if (!string.IsNullOrEmpty(context.RouteName)) { var isValidated = false; VirtualPathData bestPathData = null; INamedRouter matchedNamedRoute; if (_namedRoutes.TryGetValue(context.RouteName, out matchedNamedRoute)) { bestPathData = matchedNamedRoute.GetVirtualPath(context); isValidated = context.IsBound; } // If we get here and context.IsBound == true, then we know we have a match, we want to keep // iterating to see if we have multiple matches. foreach (var unnamedRoute in _unnamedRoutes) { // reset because we're sharing the context context.IsBound = false; var pathData = unnamedRoute.GetVirtualPath(context); if (pathData == null) { continue; } if (bestPathData != null) { // There was already a previous route which matched the name. throw new InvalidOperationException( Resources.FormatNamedRoutes_AmbiguousRoutesFound(context.RouteName)); } else if (context.IsBound) { // This is the first 'validated' match that we've found. bestPathData = pathData; isValidated = true; } else { Debug.Assert(bestPathData == null); // This is the first 'unvalidated' match that we've found. bestPathData = pathData; isValidated = false; } } if (isValidated || useBestEffort) { context.IsBound = isValidated; if (bestPathData != null) { bestPathData = new VirtualPathData( bestPathData.Router, NormalizeVirtualPath(bestPathData.VirtualPath), bestPathData.DataTokens); } return bestPathData; } else { return null; } } else { VirtualPathData bestPathData = null; for (var i = 0; i < Count; i++) { var route = this[i]; var pathData = route.GetVirtualPath(context); if (pathData == null) { continue; } if (context.IsBound) { // This route has validated route values, short circuit. return new VirtualPathData( pathData.Router, NormalizeVirtualPath(pathData.VirtualPath), pathData.DataTokens); } else if (bestPathData == null) { // The values aren't validated, but this is the best we've seen so far bestPathData = pathData; } } if (useBestEffort) { return new VirtualPathData( bestPathData.Router, NormalizeVirtualPath(bestPathData.VirtualPath), bestPathData.DataTokens); } else { return null; } } } private PathString NormalizeVirtualPath(PathString path) { var url = path.Value; if (!string.IsNullOrEmpty(url) && _options.LowercaseUrls) { var indexOfSeparator = url.IndexOfAny(new char[] { '?', '#' }); // No query string, lowercase the url if (indexOfSeparator == -1) { url = url.ToLowerInvariant(); } else { var lowercaseUrl = url.Substring(0, indexOfSeparator).ToLowerInvariant(); var queryString = url.Substring(indexOfSeparator); // queryString will contain the delimiter ? or # as the first character, so it's safe to append. url = lowercaseUrl + queryString; } return new PathString(url); } return path; } private void EnsureOptions(HttpContext context) { if (_options == null) { _options = context.RequestServices.GetRequiredService
           
            
             >().Options; } } }
            
           
          
         
        
       
      
     

 乍一看这个类的功能还是比较庞大的，我们主要关注他对IRouter接口签名的实现：

Task RouteAsync(RouteContext context)：

通过代码我们可以看到，这个方法主要对RouteCollection本身持有的Route 规则循环添加到路由上下文RouteContext.RouteData中。

VirtualPathData GetVirtualPath(VirtualPathContext context)：