Processing absent files by custom middleware
Middleware is new term for ASP.NET Core, at common this is ordinary Handler like this Как сделать простейший Web-handler - формирующий XML или JSON., but in Net Core it can be perform as function in App.Use.
In current project I have a lot of various Roots, see Asp Net Core Routing, Conventions, DefultUI. Site roots - ContentRootPath/StaticFilesRoot/WebRootPath/WebRootFileProvider/RazorPagesOptions.RootDirectory., by this approach I have redirect any request to another file and can make custom processing to any missing files (custom code, header or anything else).
254: 'Route anylizer
255: App.Use(Async Function(context As HttpContext, NextRequestDelegate As RequestDelegate)
256: Dim CurrentEndpoint = context.GetEndpoint()
257: If (CurrentEndpoint Is Nothing) Then
258: Debug.WriteLine($"RequestPath {context.Request.Path} endpoint nothing.")
259: Dim StaticOptions As StaticFileOptions = New StaticFileOptions With {.FileProvider = New PhysicalFileProvider(Builder.Configuration("StaticFilesRoot"))}
260: Dim Opt As IOptions(Of StaticFileOptions) = Options.Create(StaticOptions)
261: Dim NewEnvironment As IWebHostEnvironment = Environment
262: NewEnvironment.ContentRootPath = Builder.Configuration("StaticFilesRoot")
263: NewEnvironment.WebRootPath = Builder.Configuration("StaticFilesRoot")
264: Dim StaticMiddleware = New StaticFileMiddleware(
265: Async Function()
266: 'Await NextRequestDelegate(context)
267: Dim StaticFile As IFileInfo = Opt.Value.FileProvider.GetFileInfo(context.Request.Path)
268: If Not StaticFile.Exists Then
269: Await context.Response.WriteAsync("File is nothing")
270: Else
271: Await context.Response.SendFileAsync(StaticFile)
272: End If
273:
274: End Function,
275: NewEnvironment,
276: Opt,
277: LoggerFactory)
278: Await StaticMiddleware.Invoke(context)
279: Else
280: Debug.WriteLine($"Endpoint: {CurrentEndpoint.DisplayName}")
281: Dim Endpoint As RouteEndpoint = TryCast(CurrentEndpoint, RouteEndpoint)
282: Debug.WriteLine($"RoutePattern: {Endpoint?.RoutePattern.RawText}")
283: For j As Integer = 0 To CurrentEndpoint.Metadata.Count - 1
284: Debug.WriteLine($"Endpoint Metadata {j}: {CurrentEndpoint.Metadata(j)}")
285: Next
286: Await NextRequestDelegate(context)
287: End If
288: End Function)
289:
We also can use middlware to handle unexpected exception, like we doing that in desktop application Trap unhandled exception in windows application.. This is a pattern.
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Link to this page:
http://www.vb-net.com/StaticMiddleware/Index.htm
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