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IP Address, and such like. Very often when users ask how to do it in Server Blazor app, they are either told that it is not possible, or sometimes offered partial solutions employing JSInterop. But can it be done without resorting to JSInterop ? Here's the answer...

enet
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2 Answers2

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The fiction that the HttpContext object can't be used with Blazor Server App, has been long propagated on Stackoverflow, and it is high time to pension it off.

It is true that the HttpContext is not available when a WebSocket connection is in operation, but this must be clear: When you type an url and press the enter button, the connection to your server-side Blazor app is an HTTP connection, and not a WebSocket connection.

Thus, your app can access and use the HttpContext in the same way it is used in a Razor Pages App or a MVC App, including getting the User Agent and an IP Address. The following code sample demonstrates how to use the HttpContext to get the User Agent and IP Address natively, without using JSInterop which should be used as a last resort, and pass the extracted values to the App component.

  1. Add a file to the Pages folder and name it _Host.cshtml.cs.
  2. Add this code to the file:
public class HostModel: PageModel
{
    private readonly IHttpContextAccessor _httpContextAccssor;
    
    public HostModel(IHttpContextAccessor httpContextAccssor)
    {
        _httpContextAccssor = httpContextAccssor;    
    }

    public string UserAgent { get; set; }
    public string IPAddress { get; set; }
    
    // The following links may be useful for getting the IP Adress:
    // https://stackoverflow.com/questions/35441521/remoteipaddress-is-always-null
    // https://stackoverflow.com/questions/28664686/how-do-i-get-client-ip-address-in-asp-net-core
    
    public void OnGet()
    {
        UserAgent = _httpContextAccssor.HttpContext.Request.Headers["User-Agent"];
        // Note that the RemoteIpAddress property returns an IPAdrress object 
        // which you can query to get required information. Here, however, we pass 
        // its string representation
        IPAddress = _httpContextAccssor.HttpContext.Connection.RemoteIpAddress.ToString();  
    }
}

You may need one or more of these usings:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text.Encodings.Web;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.UI.Services;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.Extensions.Logging;
using Microsoft.AspNetCore.Http;
  1. Add the following line to your Host.cshthml page (on top of the page near to the usings and that stuff):
@model HostModel
  1. In the App component, define two parameter properties that will get and store the User Agent and IP Address passed to it from the component tag located in _Host.cshtml.

App.razor:

<p>UserAgent: @UserAgent</p>
<p>IPAddress: @IPAddress</p>

@code
{
    [Parameter]
    public string UserAgent { get; set; }

    [Parameter]
    public string IPAddress { get; set; }
}
  1. In _Host.cshtml update the component tag like this (This method is outdated now):
<app>
    <component type="typeof(App)" render-mode="ServerPrerendered" param-UserAgent="@Model.UserAgent" param-IPAddress="@Model.IPAddress" />
</app>

In current Blazor server side apps, this can be done like this:

<div>
    @(await Html.RenderComponentAsync<App>(RenderMode.Server, new { IPAddress = Model.IPAddress, UserAgent = Model.UserAgent }))
</div>
  1. Add services.AddHttpContextAccessor(); to Startup's ConfigureServices method to enable access to the HttpContext.

That is all. You can add the Identity UI to your Blazor Server App as well and apply the same procedure shown above to extract the claims principal from the HttpContext, after the user has authenticated (do that for learning purpose only, as you should use the AuthenticationStateProvider instead).

Here's also a link to the official docs about the current subject.

RhysF
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enet
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    I could have done without the HttpContextAccessor: https://github.com/aspnet/AspNetCore/issues/18070#issuecomment-570295377 – enet Jan 02 '20 at 22:25
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    Is there a version of .net core in which your instructions result in compilation? – arbitrary Feb 07 '20 at 07:53
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    So I guess I must be missing something here. Your recommended code above does seem to work and get what is needed but how do you access those new properties in _Host.cshtml.cs from other razor components or services inside the Blazor SSA? – Orgbrat Feb 07 '20 at 22:09
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    You can save them in a local storage from which components and services can read them. – enet Feb 07 '20 at 22:23
  • The `HttpContextAccessor` is not needed (any longer). You can directly reference `this.Request.HttpContext.Request.Headers["User-Agent"]` and `this.Request.HttpContext.Connection.RemoteIpAddress` once you add the `Microsoft.AspNetCore.HttpOverrides` nuget package. – FranzHuber23 Apr 16 '20 at 09:24
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    See my first comment above, where I say the HttpContextAccessor is not needed as you can directly access the HttpContext provided as a property of the ModelPage object – enet Apr 16 '20 at 09:47
  • I want to use this method to get the AccessToken from the user's Windows Identity so that later in my app I can use that AccessToken to run a method impersonated as that user. Can I use localstorage for that? Or can localstorage only store strings? – Dbloom May 07 '20 at 20:05
  • Yes, you can store the access token in the local storage. – enet May 07 '20 at 21:23
  • Is there any better way to do this with the release of Blazor with .NET 5? – OpTech Marketing Nov 22 '20 at 05:38
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    Thanks for the post, @enet. What's not mentioned is exactly how to access the IP address from any page. I've figured out a way -- add a cascading value in App.razor like this: . Then from any page, do this: [CascadingParameter(Name = "IPAddress")] public string IPAddress { get; set; }. That's it! Hope this helps someone else. – Franky Jan 05 '21 at 20:49
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    Man, you're MVP! Some of us know, that for example detecting mobile devices before anything is rendered is just useful for certain scenarios. Like a mobile version that differ not only with looks but with features. – Harry Feb 17 '21 at 06:21
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    The .NET team themselves appears to reject any workaround using the ´HttpContext´ such as this one. Any thoughts on that @enet ? Docs are horrendous a usual.Related issue: https://github.com/dotnet/aspnetcore/issues/34095 – Beltway Jul 15 '21 at 06:14
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    "The .NET team themselves appears to reject any workaround using the ´HttpContext´ such as this one." This is a baseless false statement. This is not a workaround. This is how one should code. I'm the first one to publicly show how to use the HttpContext correctly. What I show here appears in the docs over a year later (https://learn.microsoft.com/en-us/aspnet/core/blazor/security/server/additional-scenarios?view=aspnetcore-6.0#pass-tokens-to-a-blazor-server-app). It seems to me that you do not completely understand the issue and the solution. – enet Jul 15 '21 at 09:04
  • My answer starts with "The fiction that the HttpContext object can't be used with Blazor Server App", implying that it can be used. But alas, you may find other answers by me, where I'm saying that the HttpContext is not available in Blazor, and should not be used. Do I contradict myself ? Not at all. It all depends on the context. Here you fail to understand the context, etc. – enet Jul 15 '21 at 09:04
  • I get a CS1061 error in `_Hosts.cshtml` on `IPAddress` and `UserAgent` that says: `'Pages__Host' does not contain a definition for 'IPAddress' and no accessible extension method 'IPAddress' accepting a first argument of type 'Pages__Host' could be found (are you missing a using directive or an assembly reference?)` I have my public strings in `_Host.cshtml.cs` and my using statements included. Any thoughts on where to look? I seems to be a reference error between `_Hosts.cshtml` and `_Hosts.cshtml.cs`? – aterbo Oct 29 '21 at 19:08
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    While this shows how to capture the IP (it works), it fails to provide how to get that value elsewhere. In .NET 6, all the options I tried to read that value elsewhere failed. Local Storage is NOT available at that point. IMemoryCache requires a unique key that can't be defined, else you run the risk of getting a 2nd connection's IP. Cascading Parameters don't work. Scoped classes don't work (_host seems to get a different version than blazor does). The 2nd part of the two part solution here works: https://stackoverflow.com/questions/57982444/how-do-i-get-client-ip-and-browser-info-in-blazor – Mmm Feb 10 '22 at 15:31
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In Your Startup > ConfigureServices :

 services.AddControllers();

In Your Startup > Configure:

  app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
                endpoints.MapBlazorHub();
                endpoints.MapFallbackToPage("/_Host");
            });

add a folder name it : Controllers

add a controller name it : InitController

add a method like this :

   [Route("[controller]/[action]")]
    public class InitController : Controller
    {
    public IActionResult UserInfo(string redirectUri)
        {
           var request = Request.HttpContext;


            return LocalRedirect(redirectUri);
        }
}

in request varible ,all data are exists

at last for redirecting user from pages or components use this code :

@inject NavigationManager NavigationManager

@code{
     protected override Task OnInitializedAsync ()
        {       var uri = new Uri(NavigationManager.Uri)
            .GetComponents(UriComponents.PathAndQuery, UriFormat.Unescaped);

           var query = $"?redirectUri={Uri.EscapeDataString(uri)}";
          NavigationManager.NavigateTo("/Init/UserInfo" + query, forceLoad: true);
           StateHasChanged();

            return base.OnInitializedAsync();


        }
}
Soroush Asadi
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