Access HttpContext in ASP.NET Core

[JimFeng]

Thanks for your response. I'm new to ASP.NET Core and still have following questions: 1. Where should I put ConfigureServices method? 2. My current MVC5 custom helper like following: public static class HtmlHelperExt { public static IHtmlString CHGridTable(this HtmlHelper htmlHelper, DataTable dt, object htmlAttributes = null) { UrlHelper url = new UrlHelper(HttpContext.Current.Request.RequestContext); string urlEdit = url.RouteUrl("Default"); ...... } ......//many other custom helpers } How can I inject the IActionContextAccessor and use it in my custom helper CHGridTable and other helpers? 3. How can I use the ContextAccessor to get info for the code lines below: UrlHelper url = new UrlHelper(HttpContext.Current.Request.RequestContext); string urlEdit = url.RouteUrl("Default");

[Vincent Maverick Durano]

JimFeng wrote:

I'm new to ASP.NET Core and still have following questions:

1. Where should I put ConfigureServices method?

Configuring services should be placed inside startup.cs. For more details, see: ASP.NET Core fundamentals | Microsoft Docs[^]

JimFeng wrote:

How can I inject the IActionContextAccessor and use it in my custom helper CHGridTable and other helpers?

While it may be possible, I would still recommend you to convert your static/extension class into a service whose concrete implementation would use the IHttpContextAccessor as a dependency that can be injected via its constructor just like what I've showed you on my first reply. If you still want to follow the static class approach then you could try this:

public static class HtmlHelperExt{
private static IHttpContextAccessor _httpContextAccessor;
private static IUrlHelperFactory _urlHelperFactory;
public static void SetHttpContextAccessor(IHttpContextAccessor accessor, IUrlHelperFactory urlHelperFactory) {
_httpContextAccessor = accessor;
_urlHelperFactory = urlHelperFactory;
}

public static IHtmlString CHGridTable(this HtmlHelper htmlHelper, DataTable dt, object htmlAttributes = null)
{
        var urlHelper = \_urlHelperFactory.GetUrlHelper(\_httpContextAccessor.HttpContext);
        string urlEdit = urlHelper.RouteUrl("Default");
        //rest of the stuff here
}

}

In the Startup.ConfigureServices method you can call services.BuildServiceProvider() to get the IServiceProvider to resolve the type you seek. For example:

public void ConfigureServices(IServiceCollection service) {

services.AddMvc();

//this would have been done by the framework any way after this method call;
//in this case you call the BuildServiceProvider manually to be able to use it
var serviceProvider = services.BuildServiceProvider();

//here is where you set you accessor and url helper factory
var accessor = serviceProvider.GetService

[JimFeng]

Thanks again for your patient. when I code following: var urlHelper = _urlHelperFactory.GetUrlHelper(_httpContextAccessor.HttpContext); and got the following error: Argument 1: cannot convert from 'Microsoft.AspNetCore.Http.HttpContext' to 'Microsoft.AspNetCore.Mvc.ActionContext' the error was caused by argument: _httpContextAccessor.HttpContext

[Richard Deeming]

asp.net core - how to get IUrlHelper from inside Html helper - Stack Overflow[^] Correcting the typo in that answer gives:

public static IHtmlContent CHGridTable<TModel>(this IHtmlHelper<TModel> htmlHelper, DataTable dt, object htmlAttributes = null)
{
var urlHelperFactory = (IUrlHelperFactory)htmlHelper.ViewContext.HttpContext.RequestServices.GetService(typeof(IUrlHelperFactory));
var urlHelper = urlHelperFactory.GetUrlHelper(htmlHelper.ViewContext);
string urlEdit = url.RouteUrl("Default");
...
}

You might also want to consider whether a custom tag helper might be a better choice for what you're trying to do: Tag Helpers in ASP.NET Core | Microsoft Docs[^]

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[Vincent Maverick Durano]

Hmm.. it's really hard to test it out without a dev machine. Anyway instead of passing IHttpContextAccessor, try to pass the IActionContextAccessor instead. For example in your Helper class, you can do:

private static IActionContextAccessor \_actionContextAccessor;
private static IUrlHelperFactory \_urlHelperFactory;
public static void SetHttpContextAccessor(IActionContextAccessor accessor, IUrlHelperFactory urlHelperFactory) {
    \_actionContextAccessor = accessor;
    \_urlHelperFactory = urlHelperFactory;
}

then you can do:

var urlHelper = _urlHelperFactory.GetUrlHelper(_actionContextAccessor.ActionContext);

and finally, configure the IActionContextAccessor in Startup.ConfigureServices method:

var accessor = serviceProvider.GetService()
var userHelperFactory = serviceProvider.GetService()
HtmlHelperExt.SetHttpContextAccessor(accessor,userHelperFactory);

You could also try what's suggested by Richard.

[JimFeng]

Thanks, I corrected error in my custom helper, but when I call the helper from views as following: @HtmlHelperExt.CHGridTable(Model, new { tablename = "tblTest", defaultcolsort = "3" }) and got following error: Error CS0411 The type arguments for method 'HtmlHelperExt.CHGridTable(HtmlHelper, DataTable, object)' cannot be inferred from the usage. Try specifying the type arguments explicitly. The call on MVC5 works file, How can I use the custom helper on view of Core Web Application (MVC6): The custom helper code as following: public static IHtmlContent CHGridTable(this HtmlHelper htmlHelper, DataTable dt, object htmlAttributes = null) { var urlHelperFactory = (IUrlHelperFactory)htmlHelper.ViewContext.HttpContext.RequestServices.GetService(typeof(IUrlHelperFactory)); var url = urlHelperFactory.GetUrlHelper(htmlHelper.ViewContext); ...... return new HtmlString(tbBtnAdd.ToString() + tbGridTable.ToString() + script.ToString()); }

[Richard Deeming]

JimFeng wrote:

@HtmlHelperExt.CHGridTable(Model, new { tablename = "tblTest", defaultcolsort = "3" })

That should probably be:

@Html.CHGridTable(Model, new { tablename = "tblTest", defaultcolsort = "3" })

You need to call it as an extension method on the IHtmlHelper instance, not call the static method directly.

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[JimFeng]

@Html.CHGridTable(......) works on MVC5 but not ASP.NET Core MVC.

[Richard Deeming]

Have you imported the tag helpers from your assembly? /Views/_ViewImports.cshtml:

@addTagHelper *, YourAssemblyNameHere

Managing Tag Helper scope | Tag Helpers in ASP.NET Core | Microsoft Docs[^]

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[JimFeng]

I added @addTagHelper *, HtmlHelperExt in _ViewImports.cshtml file but still got error: Error: CS1061 'IHtmlHelper' does not contain a definition for 'CHDropdownMenu' and no accessible extension method 'CHDropdownMenu' accepting a first argument of type 'IHtmlHelper' could be found (are you missing a using directive or an assembly reference?) on the View page like this (the same as on MVC 5): @model System.Data.DataSet @using HtmlHelperExt; ...... @Html.CHDropdownMenu(Model, "mnuSample1", new { MenuOpenType = "Hover" }) ...... My Custom helper like this: namespace HtmlHelperExt { public static class HtmlHelperExt { public static IHtmlContent CHDropdownMenu(this HtmlHelper htmlHelper, DataSet ds, string divID, object htmlAttributes = null) { ...... return new HtmlString(tbDiv_Menu.ToString()); } } }

[Richard Deeming]

JimFeng wrote:

IHtmlHelper<dataset>' does not contain a definition for 'CHDropdownMenu'

CHDropdownMenu<tmodel>(this HtmlHelper<tmodel> htmlHelper,

You need to declare the helper method as an extension method against the IHtmlHelper interface, not the HtmlHelper class.

public static IHtmlContent CHDropdownMenu<TModel>(this IHtmlHelper<TModel> htmlHelper, ...

IHtmlHelper Interface (Microsoft.AspNetCore.Mvc.Rendering) | Microsoft Docs[^]

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[JimFeng]

My assembly is a custom HtmlHelper NOT TagHelper.

[Richard Deeming]

Yes, of course. :doh: You'll want @using statements for your namespace, rather than @addTagHelper statements. Still in the _ViewImports.cshml file, though.

@using HtmlHelperExt

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[JimFeng]

@using HtmlHelperExt is already in the _ViewImports.cshml, but got the same error.

[Richard Deeming]

Did you change the first parameter of the extension method, as I suggested yesterday?

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[JimFeng]

Thank you Rick, after I changed the parm type, and the helper works in my ASP.NET Core 2.1 MVC app.