WIP article release 0.23

src/Website/articles/20231011-bolero-0-23-released.md

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+---
+title: Bolero 0.23 released
+subtitle: Router query parameters and .NET 8 compatibility
+---
+
+We are happy to announce the release of [Bolero](https://fsbolero.io) version 0.23.
+Bolero is a library that enables writing full-stack applications in F#, whose client side runs in WebAssembly using Blazor.
+
+The main highlights of this release are:
+* Improvements to routing, including query parameters, not-found handling and hash scrolling.
+* .NET 8 compatibility.
+* Better C# compatibility for server-side.
+
+Install the latest project template with:
+
+```
+dotnet new -i Bolero.Templates::0.23.TODO
+```
+
+## Routing improvements
+
+### Query parameters ([#309](https://github.com/fsbolero/Bolero/issues/309))
+
+Inferred routers can now handle query parameter parsing. It is done using the syntax `?paramName={fieldName}`.
+
+```fsharp
+type Page =
+    | [<EndPoint "/">] Home
+    | [<EndPoint "/articles?page={pageNum}&count={countPerPage}"] Articles of pageNum: int * countPerPage: int
+```
+
+Using the router above, `/articles?page=3&count=20` corresponds to the page value `Articles (3, 20)`.
+
+Query parameters are optional if the corresponding field has type `option` or `voption`, and mandatory otherwise.
+
+Additionally, the syntax `?{paramName}` is short for `?paramName={paramName}`.
+
+```fsharp
+type Page =
+    | [<EndPoint "/articles?{tag}&{page}&{count}"] Articles of tag: string option * page: int option * count: int
+```
+
+Using the router above, `/articles?tag=fsharp&count=20` corresponds to the page value `Articles (Some "fsharp", None, 20)`.
+
+Of course, path parameters and query parameters can be mixed in the same endpoint.
+
+```fsharp
+type Page =
+    | [<EndPoint "/articles/{tag}?{page}"] Articles of tag: string * page: int option
+```
+
+Using the router above, `/articles/fsharp?page=20` corresponds to the page value `Articles ("fsharp", Some 20)`.
+
+* [#308](https://github.com/fsbolero/Bolero/issues/308) Add router functions to decide what to do when the URL is invalid.
+
+    * `Router.withNotFound` takes an endpoint to redirect to, and applies to a `Router<_, _, _>` (ie. an inferred router).
+
+    * `Router.withNotFoundMsg` takes an Elmish message to send, and applies to any `IRouter<_, _>` (including manual routers).
+
+    These functions apply when the initial URL is invalid, or when the URL is programmatically changed to be invalid.
+    They do not apply when the user clicks a link to an invalid URL, in order to allow external links.
+
+* [#309](https://github.com/fsbolero/Bolero/issues/309) Add support for query parameters in inferred routing with `EndPointAttribute`.
+
+    * `?paramName={fieldName}` adds query parameter `paramName` corresponding to the union field named `fieldName`. This parameter is mandatory if `fieldName` is a string, boolean or number, and optional if it is an option or voption of these types.
+
+    * `?{paramName}` is short for `?paramName={paramName}`.
+
+* [#313](https://github.com/fsbolero/Bolero/issues/313) Improve C# compatibility of server-side APIs.
+    For the following extension methods:
+
+    * `IServiceCollection.AddBoleroHost`
+    * `IServiceCollection.AddBoleroRouting`
+    * `IEndpointRouteBuilder.MapFallbackToBolero`
+
+    The following changes are applied:
+
+    * Optional arguments are changed from F#-style to C#-style. This is a source breaking change for callers who use explicit syntax `?argument = optionValue`.
+    * Function arguments are changed from F#-style functions to C#-style `Func` or `Action`.
+
+* [#315](https://github.com/fsbolero/Bolero/issues/315) Support adding hash component to routing URLs:
+
+    * Manually adding `+ "#foo"` to a routed URL will correctly scroll to the element named `foo` in the target page.
+
+    * Methods `IRouter.Link` and `IRouter.HRef` take a new optional argument `hash: string` to link to the corresponding `#hash` in the target page.
+
+* [#316](https://github.com/fsbolero/Bolero/issues/316) Fix `on.stopPropagation` and `on.preventDefault` to take event names without the `on` prefix, for consistency with `on.event`.
+
+* [#317](https://github.com/fsbolero/Bolero/issues/317) Fix .NET 8 compatibility of the MSBuild task for scoped CSS.
+
+* [#317](https://github.com/fsbolero/Bolero/issues/317) Fix .NET 8 compatibility of the server-side rendering of nodes.
+
+* [#323](https://github.com/fsbolero/Bolero/issues/323) Use `WheelEventArgs` for wheel events and `ErrorEventArgs` for `on.error`.
+
+