Web Context

Both in Sitelets and Rpc functions, WebSharper provides a value of type WebSharper.Web.Context that gives some contextual information about the current request.

Retrieving the context

Sitelets

In Sitelets, the context provided by content-generating functions such as Content.Page or Content.Custom implements Web.Context, so you can use it directly.

Rpc functions

In Rpc functions, the context can be retrieved using the function WebSharper.Web.Remoting.GetContext(). Be careful to only call it from the thread from which your function was called. A typical Rpc has the following structure:

open WebSharper
open WebSharper.Web

[<Rpc>]
let MyRpcFunction () =
    // Retrieve the context outside of the async {} expression.
    let context = Remoting.GetContext()
    async {
        // Once retrieved, use the context at will here.
        return System.IO.File.ReadAllText(context.RootFolder + "/someContent.txt")
    }

User Sessions

The main reason to use the context is to manage user sessions. The member UserSession has the following members:

• LoginUser : username: string * ?persistent: bool -> Async<unit>

  Logs in the user with the given username. This sets a cookie that is uniquely associated with this username. Set persistent to true if the user session should last beyond the user's current browser session.

• LoginUser : username: string * duration: TimeSpan -> Async<unit>

  Logs in the user with the given username. This sets a cookie that is uniquely associated with this username. The user session should last for the given duration.

• GetLoggedInUser : unit -> Async<string option>

  Retrieves the currently logged in user's username, or None if the user is not logged in.

• Logout : unit -> unit

  Logs the user out.

The implementation of these functions relies on cookies and thus requires that the browser has enabled cookies.

Other Context functionality

• ApplicationPath : string is the virtual application path of the server.

• RootFolder : string is the physical folder on the server machine from which the application is running.

• RequestUri : Uri is the URI of the request.

• ResolveUrl : string -> string resolves URL paths starting with ~ into absolute paths prefixed with the ApplicationPath.

• Environment : Dictionary<string, obj> is a host-dependent environment.

  • On ASP.NET Core, this contains the following items:

    • Under key "WebSharper.AspNetCore.HttpContext", the HTTP context, of type Microsoft.AspNetCore.Http.HttpContext.

    • Under key "WebSharper.AspNetCore.Services", the dependency injection service provider, of type Microsoft.Extensions.DependencyInjection.IServiceProvider.

  • On ASP.NET 4.x, this contains the following item:

    • Under key "HttpContext", the HTTP context, of type System.Web.HttpContextBase.

  • On OWIN, this contains the OWIN environment proper. Additionally, if this is OWIN on ASP.NET 4.x (using Microsoft.Owin.Host.SystemWeb), the above "HttpContext" key is added to the environment.