了解到了OrchardCore主要由两个中间件(ModularTenantContainerMiddleware和ModularTenantRouterMiddleware)构成，下面开始了解ModularTenantContainerMiddleware中间件第一行代码。
了解asp.net core机制的都知道中间件是由构造函数和Invoke(或者InokeAsync)方法构成，构造函数不过就是个依赖注入的过程，Invoke也可以直接依赖注入，两者的区别是构造函数时全局的，Invoke只是当次请求，所以从Inovke开始了解！
public async Task Invoke(HttpContext httpContext) { // Ensure all ShellContext are loaded and available. await _shellHost.InitializeAsync(); var shellSettings = _runningShellTable.Match(httpContext); // We only serve the next request if the tenant has been resolved. if (shellSettings != null) { if (shellSettings.State == TenantState.Initializing) { httpContext.Response.Headers.Add(HeaderNames.RetryAfter, "10"); httpContext.Response.StatusCode = StatusCodes.Status503ServiceUnavailable; await httpContext.Response.WriteAsync("The requested tenant is currently initializing."); return; } // Makes 'RequestServices' aware of the current 'ShellScope'. httpContext.UseShellScopeServices(); var shellScope = await _shellHost.GetScopeAsync(shellSettings); // Holds the 'ShellContext' for the full request. httpContext.Features.Set(new ShellContextFeature { ShellContext = shellScope.ShellContext, OriginalPath = httpContext.Request.Path, OriginalPathBase = httpContext.Request.PathBase }); await shellScope.UsingAsync(scope => _next.Invoke(httpContext)); } }