How do I get client IP and browser info in Blazor?

Question

How do I get client information such as IP adress and browser name/version in Blazor server-side?

Answer 1

If you use Cloud Flare on your site, Do not use the following code:

var ipAddress = HttpContext?.Connection?.RemoteIpAddress;

The previous code will not fetch the client’s IP address, but rather it will fetch the IP of Cloud Flare servers

---

Best Way to Retrieve a Client's IP Address Behind Cloudflare

When using Cloudflare, using HttpContext.Connection.RemoteIpAddress will fetch Cloudflare’s IP address instead of the client’s actual IP.

Recommended Approach

Cloudflare provides the CF-Connecting-IP header, which contains the client’s true IP address. Additionally, the X-Forwarded-For header can also be useful.

Solution Using an Extension Method

Here’s a concise way to get the real client IP address using HttpContext:

string GetUserIpAddress(HttpContext context)
{
    // Check CF-Connecting-IP header
    if (!string.IsNullOrEmpty(context.Request.Headers["CF-CONNECTING-IP"]))
        return context.Request.Headers["CF-CONNECTING-IP"];

    // Check X-Forwarded-For header
    if (!string.IsNullOrEmpty(context.Request.Headers["X-Forwarded-For"]))
        return context.Request.Headers["X-Forwarded-For"];

    // Fallback to RemoteIpAddress
    return context.Connection.RemoteIpAddress?.ToString();
}

Explanation:

1. CF-Connecting-IP: Check for the presence of this header set by Cloudflare to get the client’s IP.

2. X-Forwarded-For: If the above header is not available, check this standard header.

3. RemoteIpAddress: As a last resort, use the remote IP address, which may still point to Cloudflare’s servers.

This approach ensures you get the correct client IP whether behind Cloudflare or not.

---

Answer 2

In Blazor Web App 8:

Prerendering mode can get the status passed by App.razor, But after the second OnInitialized event, the status will be emptied. So you need to use PersistentComponentState to retain the state

1. Create a CascadingParameter SharedStorage(You can also use it as a Scope domain object dependency injection)

SharedStorage.cs

public class SharedStorage
{
    public const string KEY_IPADDRESS = "IPAddress";
    public string IPAddress { get; set; } = null!;
}

Program.cs

 builder.Services.AddCascadingValue("SharedStorage", sp =>{
   return new SharedStorage();});

2. Get IP and other information in App.razor

APP.razor

@code {
    [CascadingParameter]
    public HttpContext? HttpContext { get; set; }
    [CascadingParameter(Name = "SharedStorage")]
    public SharedStorage? SharedStorage { get; set; }

    protected override async Task OnInitializedAsync()
    {
        await base.OnInitializedAsync();
        string? ip = null;
        if (HttpContext != null && SharedStorage != null)
        {   
            //You can refer to other answers
            SharedStorage.IPAddress = HttpContext.GetIpAddress();
        }
    }
}

3. In any razor component

Pass prerender variables using PersistentComponentState

@rendermode InteractiveServer
@implements IDisposable
@inject PersistentComponentState ApplicationState

private string? ipAddress;

[CascadingParameter(Name = "SharedStorage")]
public SharedStorage? SharedStorage { get; set; }

private PersistingComponentStateSubscription? 
persistingComponentStateSubscription;

protected override async Task OnInitializedAsync()
{
    await base.OnInitializedAsync();
    if (SharedStorage?.IPAddress != null)
    {
        persistingComponentStateSubscription = ApplicationState.RegisterOnPersisting(Persist);
    }
    else
    {
        var isSucceed = ApplicationState.TryTakeFromJson<string>(SharedStorage.KEY_IPADDRESS, out ipAddress);
    }

}

private Task Persist()
{
    ApplicationState.PersistAsJson(SharedStorage.KEY_IPADDRESS, SharedStorage?.IPAddress);
    return Task.CompletedTask;
}


public void Dispose()
{
    persistingComponentStateSubscription?.Dispose();
}

Answer 3

in Blazor 8 :

Program.cs:

builder.Services.AddHttpContextAccessor();

Index.razor:

  @inject IHttpContextAccessor httpContextAccessor; 
  @code{
var remoteIpAddress =httpContextAccessor.HttpContext.Connection?.RemoteIpAddress.ToString();}

Answer 4

Also answered in: Get user-agent and ip in Blazor server-side app

There's numerous examples of what to add to _Host.cshtml.cs to get an anti-forgery token. You can piggy-back that by adding to that code in _Host.cshtml as follows:

@{
    var initialTokenState = new InitialApplicationState
        {
            XsrfToken = Xsrf.GetAndStoreTokens(HttpContext).RequestToken,
            Cookie = HttpContext.Request.Cookies[".AspNetCore.Cookies"]
        };
    // try X-Forwarded-For first
    HttpContext.Request.Headers.TryGetValue("X-Forwarded-For", out var forwardedFor);
    if (forwardedFor.Count > 0)
        initialTokenState.RemoteIp = forwardedFor[0];
    else
        initialTokenState.RemoteIp = HttpContext.Connection.RemoteIpAddress?.ToString();
}

This exists for the life of the circuit and there's no way the remote IP changes while a circuit exists.

This answer only solves the client IP address half of the question.

Answer 5

This is to clarify the existing accepted answer on how to get the Remote AP address of a user in Blazor server. You would think this would be easy, but because Blazor server runs outside of the normal context of a asp.net core app, there are complexities.

Thus the direct use of HttpContextAccess is not recommended within a Blazor Component. So even though it appears that you can easily access it in a component, you should not do so.

The recommended approach is to use the HttpAccessor in _host.cshtml (where it is ok to use it), and then pass this information to app.razor, which can then pass it to the rest of the app through a cascading parameter, or by updating a scoped dependency.

Here is an example using a scoped dependency:

The class that will be used as a scoped dependency:

public class BlazorAppContext
{
    /// <summary>
    /// The IP for the current session
    /// </summary>
    public string CurrentUserIP { get; set; }
}

Add to Program.cs

  builder.Services.AddScoped<BlazorAppContext>();
  builder.Services.AddHttpContextAccessor()

Update _host.cshtml as follows:

 @inject IHttpContextAccessor httpContextAccessor;
 @{
     var remoteIpAddress = 
    httpContextAccessor.HttpContext.Connection?.RemoteIpAddress.ToString();
  }

 ...
 <component type="typeof(App)" param-RemoteIpAddress=remoteIpAddress 
 render-mode="Server" />

Now update App.razor

[Parameter]
public string? RemoteIpAddress { get; set; }

[Inject]
BlazorAppContext BlazorAppContext { get; set; }

protected override async Task OnInitializedAsync()
{
    this.BlazorAppContext.CurrentUserIP = this.RemoteIpAddress;
}

The app is now set up so that the BlazorAppContext will have the correct IP address or any component that needs it through injection.

Answer 6

Here's how to do it in server side Blazor for .NET 5 in 2021.

Please note that my solution will only provide you an IP address, but getting an user agent should be easy using my solution.

I will just copy the contents of my blog post available here: https://bartecki.me/blog/Blazor-serverside-get-remote-ip

TLDR:

You can use JavaScript to call your own exposed endpoint that will return remote connection IP using following code:

RemoteIpAddress = Request.HttpContext.Connection.RemoteIpAddress.ToString() 

... with the downside of having to handle your reverse proxy server if you have any, otherwise you will just get your reverse proxy's IP address.

or you can call an external endpoint using JavaScript that will return an IP address for you with the downside that you will have to configure CORS and even then it can be blocked by some adblocking extensions.

Details:

Two approaches

Approach 1: Call an external service using JavaScript

Pros:

• Slightly more simpler if you are using reverse proxy like nginx, traefik

Cons:

• May be blocked by external extensions/adblockers
• You will have to configure CORS

_Host.cshtml

<script>
  window.getIpAddress = () => {
    return fetch('https://jsonip.com/')
      .then((response) => response.json())
      .then((data) => {
        return data.ip
      })
  }
</script>

RazorPage.razor.cs

    public partial class RazorPage : ComponentBase
    {
        [Inject] public IJSRuntime jsRuntime { get; set; }

        public async Task<string> GetIpAddress()
        {
            try
            {
                var ipAddress = await jsRuntime.InvokeAsync<string>("getIpAddress")
                    .ConfigureAwait(true);
                return ipAddress;
            }
            catch(Exception e)
            {
                //If your request was blocked by CORS or some extension like uBlock Origin then you will get an exception.
                return string.Empty;
            }
        }
    }

Startup.cs

        public void ConfigureServices(IServiceCollection services)
        {
            //code...
            services
                .AddCors(x => x.AddPolicy("externalRequests",
                    policy => policy
                .WithOrigins("https://jsonip.com")));
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            //code...
            app.UseCors("externalRequests");
        }

Approach 2: Expose an endpoint in our Blazor app and call it using JavaScript

Pros:

• You won't have to configure CORS
• Won't be blocked by extensions or adblockers

Cons:

• May be slightly more complicated if you are using a reverse proxy like nginx, traefik, etc.

Now take care as you will use this approach, because if you are using a reverse proxy, then you will actually receive your reverse proxy IP address. It is very possible that your reverse proxy is already forwarding an IP address of the external client in some sort of header, but it is up to you to figure it out.

Example: https://www.nginx.com/resources/wiki/start/topics/examples/forwarded/

InfoController.cs

    [Route("api/[controller]")]
    [ApiController]
    public class InfoController : ControllerBase
    {
        [HttpGet]
        [Route("ipaddress")]
        public async Task<string> GetIpAddress()
        {
            var remoteIpAddress = this.HttpContext.Request.HttpContext.Connection.RemoteIpAddress;
            if (remoteIpAddress != null)
                return remoteIpAddress.ToString();
            return string.Empty;
        }
    }

Startup.cs

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers(); //remember to map controllers if you don't have this line
                endpoints.MapBlazorHub();
                endpoints.MapFallbackToPage("/_Host");
            });

_Host.cshtml

<script>
  window.getIpAddress = () => {
    return fetch('/api/info/ipaddress')
      .then((response) => response.text())
      .then((data) => {
        return data
      })
  }
</script>

RazorPage.razor.cs

    public partial class RazorPage : ComponentBase
    {
        [Inject] public IJSRuntime jsRuntime { get; set; }

        public async Task<string> GetIpAddress()
        {
            try
            {
                var ipAddress = await jsRuntime.InvokeAsync<string>("getIpAddress")
                    .ConfigureAwait(true);
                return ipAddress;
            }
            catch(Exception e)
            {
                //If your request was blocked by CORS or some extension like uBlock Origin then you will get an exception.
                return string.Empty;
            }
        }
    }

Answer 7

Well, I came across this issue this morning and the way I solved it for server-side Blazor was to create a class that you can then inject as a scoped service on your _host.cshtml, and then access it anywhere on your Blazor components, as Razor pages already have support for this.

    public class BlazorAppContext
    {
        /// <summary>
        /// The IP for the current session
        /// </summary>
        public string CurrentUserIP { get; set; }
    }

Startup.cs:

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
      ...

      services.AddScoped<BlazorAppContext>();

      ...
    }

_host.cshtml:

@inject IHttpContextAccessor httpContextAccessor
@{
    BlazorAppContext.CurrentUserIP =   httpContextAccessor.HttpContext.Connection?.RemoteIpAddress.ToString();
}

You can also try a Scoped approach that you can then use through DI.

Annotation:

As stated in the documentation, "Blazor WebAssembly apps don't currently have a concept of DI scopes. Scoped-registered services behave like Singleton services. However, the Blazor Server hosting model supports the Scoped lifetime. In Blazor Server apps, a scoped service registration is scoped to the connection. For this reason, using scoped services is preferred for services that should be scoped to the current user, even if the current intent is to run the client-side in the browser."

I hope it helps.

Answer 8

In aspnetcore3.1 this works for me:

1. Make special class for holding required info:

public class ConnectionInfo
{
    public string RemoteIpAddress { get; set; } = "-none-";
}

2. Create instance in _Host.cshtml and pass to App component as parameter:

@{
    var connectionInfo = new ConnectionInfo() 
    { 
        RemoteIpAddress = Request.HttpContext.Connection.RemoteIpAddress.ToString() 
    };
}
...
<component type="typeof(App)" 
           render-mode="ServerPrerendered"
           param-ConnectionInfo="connectionInfo" />

3. In App.razor catch and re-publish as CascadingValue:

<CascadingValue Value="connectionInfo">
  <Router AppAssembly="typeof(Program).Assembly">
      ...
  </Router>
</CascadingValue>

@code {
    [Parameter]
    public ConnectionInfo? connectionInfo { get; set; }
}

4. Obtain in any child page/component as CascadingParameter:

@code {
    [CascadingParameter]
    private ConnectionInfo? connectionInfo { get; set; }
}

The only problem here is with roaming users - when user changes his IP address and Blazor does not "catch" this (for example browser tab in background) you will have old IP address until user refreshes (F5) page.

Answer 9

Note that this is only referring to server-side Blazor.

"There is no a good way to do this at the moment. We will look into how we can provide make this information available to the client."

Source: Blazor dev at Github

Workaround

The client makes an ajax call to the server, which then can pick up the local ip number. Javascript:

window.GetIP = function () {
    var token = $('input[name="__RequestVerificationToken"]').val();
    var myData = {}; //if you want to post extra data
    var dataWithAntiforgeryToken = $.extend(myData, { '__RequestVerificationToken': token });
    var ip = String('');
    $.ajax({
        async: !1, //async works as well 
        url: "/api/sampledata/getip",
        type: "POST",
        data: dataWithAntiforgeryToken,
        success: function (data) {
            ip = data;
            console.log('Got IP: ' + ip);
        },
        error: function () {
            console.log('Failed to get IP!');
        }
    });
    return ip;
};

Backend (ASP.NET Core 3.0):

    [HttpPost("[action]")]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public string GetIP()
    {
        return HttpContext.Connection.RemoteIpAddress?.ToString();
    }

Note that this is not secure, the ipnumber can be spoofed so don't use for anything important.