.NET Core Middleware - access IApplicationBuilder in a controller? - asp.net-core

Question

I need to access IApplicationBuilder inside a controller.
What I have tried :-
I have written middleware (app.UseMyMiddleware) as follows
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env, IHttpContextAccessor httpContextAccessor)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();
app.UseMyMiddleware();
app.UseAuthentication();
app.UseSession();
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
});
}
public class MyMiddleware
{
private readonly RequestDelegate _next;
public MyMiddleware(RequestDelegate next)
{
_next = next;
}
public async Task Invoke(HttpContext context)
{
///TODO - Pass IApplicationBuilder to HttpContext
await _next(context);
}
}
public static class MiddlewareExtensions
{
public static IApplicationBuilder UseMyMiddleware(this IApplicationBuilder builder)
{
return builder.UseMiddleware<MyMiddleware>();
}
}
but I can't figure out how I can pass IApplicationBuilder to HttpContext in Invoke method. so, that I can use it in a controller.
I have also referred following stackoverflow question-answer
how to access IApplicationBuilder in a controller?
.Net Core Middleware - Getting Form Data from Request
Question(s) :-
How can pass IApplicationBuilder to HttpContext in Invoke method to use it in controller?
Is there any better way to access IApplicationBuilder inside controller apart from middleware?

Answer 1

IApplicationBuilder was not designed to work the way you want it to. Instead, if you have some data created at build time that you want to be available to middleware add a Singleton to the services and inject the singleton into the middleware.

Answer 2

You cannot access IApplicationBuilder anywhere later after completing the application building phase (after running Configure method). It's not available for injection at all.
However for the purpose of plugging-in or configuring middlewares at runtime based on request data (from HttpContext), you can use .UseWhen. Another one for terminal middleware is .MapWhen but I think that's not for your case. Here is an example of .UseWhen:
public static class MiddlewareExtensions
{
public static IApplicationBuilder UseMyMiddleware(this IApplicationBuilder builder)
{
var allOptions = new [] {"option 1","option 2"};
foreach(var option in allOptions){
var currentOption = option;
builder.UseWhen(context => {
//suppose you can get the user's selected option from query string
var selectedOption = context.Request.Query["option_key"];
return selectedOption == currentOption;
}, app => {
//your MyMiddleware is supposed to accept one argument
app.UseMiddleware<MyMiddleware>(currentOption);
});
}
return builder;
}
}
To simplify it I suppose your options are just strings, you must know beforehand all possible options that the user can select via UI. Each one will be an exact match for the condition to plug-in a middleware and they must be all exclusive (so just one of them can enable one corresponding middleware), otherwise there will be duplicate middlewares, which may cause some issue.
By expressing the foreach above more clearly, it may represent something as follows:
//kind of pseudo code
if(selectedOption1){
app.UseMiddleware<MyMiddleware>("option 1");
} else if(selectedOption2){
app.UseMiddleware<MyMiddleware>("option 2");
}
...
You must decide how you get the selected option from the user (in the example above I get it from query string). You can get it from Cookie as well (to remember the user's selection) or from other sources such as route data, headers, form, request body. I think that's another issue, so if you have problem with that, please ask in another question.

Answer 3

First up all thanks to #Kingking and #GlennSills for there solution and valuable comments.
I have solved this problem as
Created one class which inherit from Hangfire.JobStorage as follows
public class HangfireSqlServerStorageExtension : Hangfire.JobStorage
{
private readonly HangfireSqlServerStorage _hangfireSqlServerStorage = new HangfireSqlServerStorage();
public HangfireSqlServerStorageExtension(string nameOrConnectionString)
{
_hangfireSqlServerStorage.SqlServerStorageOptions = new SqlServerStorageOptions();
_hangfireSqlServerStorage.SqlServerStorage = new SqlServerStorage(nameOrConnectionString, _hangfireSqlServerStorage.SqlServerStorageOptions);
}
public HangfireSqlServerStorageExtension(string nameOrConnectionString, SqlServerStorageOptions options)
{
_hangfireSqlServerStorage.SqlServerStorageOptions = options;
_hangfireSqlServerStorage.SqlServerStorage = new SqlServerStorage(nameOrConnectionString, _hangfireSqlServerStorage.SqlServerStorageOptions);
}
public void UpdateConnectionString(string nameOrConnectionString)
{
_hangfireSqlServerStorage.SqlServerStorage = new SqlServerStorage(nameOrConnectionString, _hangfireSqlServerStorage.SqlServerStorageOptions);
}
public override IStorageConnection GetConnection()
{
return _hangfireSqlServerStorage.SqlServerStorage.GetConnection();
}
public override IMonitoringApi GetMonitoringApi()
{
return _hangfireSqlServerStorage.SqlServerStorage.GetMonitoringApi();
}
}
HangfireSqlServerStorage.cs
Used in HangfireSqlServerStorageExtension class above
public class HangfireSqlServerStorage
{
public SqlServerStorage SqlServerStorage { get; set; }
public SqlServerStorageOptions SqlServerStorageOptions { get; set; }
}
Startup.cs
In Startup file add singleton service for HangfireSqlServerStorageExtension instance and configure hangfire dashboard as follows
public class Startup
{
///Other necessary code here
public static HangfireSqlServerStorageExtension HangfireSqlServerStorageExtension { get; private set; }
public void ConfigureServices(IServiceCollection services)
{
///Other necessary code here
HangfireSqlServerStorageExtension = new HangfireSqlServerStorageExtension("DBConnecttionString"));
services.AddSingleton<HangfireSqlServerStorageExtension>(HangfireSqlServerStorageExtension);
services.AddHangfire(configuration => configuration.SetDataCompatibilityLevel(CompatibilityLevel.Version_170));
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env, IHttpContextAccessor httpContextAccessor)
{
//Other necessary code here
app.UseHangfireDashboard("/Dashboard", new DashboardOptions(), HangfireSqlServerStorageExtension);
//Other necessary code here
}
}
Inside controller I have used it as follows
HangfireController.cs
public class HangfireController : Controller
{
protected readonly HangfireSqlServerStorageExtension
hangfireSqlServerStorageExtension;
public HangfireController(HangfireSqlServerStorageExtension hangfireSqlServerStorageExtension)
{
this.hangfireSqlServerStorageExtension = hangfireSqlServerStorageExtension;
}
public IActionResult DisplayHangfireDashboard()
{
// Update connString as follows
hangfireSqlServerStorageExtension.UpdateConnectionString(connString);
var hangfireDashboardUrl = $"{this.Request.Scheme}://{this.Request.Host}{this.Request.PathBase}" + "/Dashboard";
return Json(new { url = hangfireDashboardUrl });
}
}