Get current Url in a Blazor component

Question

Get current Url in a Blazor component

asp.net-core blazor c#

Question

I need to know the url of the current page in order to check if I have to apply certain style to a element. The code below is an example.

@using Microsoft.AspNetCore.Blazor.Services
@inject IUriHelper UriHelper
@implements IDisposable

<h1>@url</h1>
<nav>
    <div class="nav-wrapper">
        <a href="#" class="brand-logo">Blazor</a>
        <ul id="nav-mobile" class="right hide-on-med-and-down">
            <li>
                <NavLink href="/" Match=NavLinkMatch.All>
                    Home
                </NavLink>
            </li>
            <li>
                <NavLink href="/counter">
                    Counter
                </NavLink>
            </li>
            <li>
                <NavLink href="/fetchdata">
                    Fetch data
                </NavLink>
            </li>
        </ul>
    </div>
</nav>

@functions {

    private string url = string.Empty;

    protected override void OnInit()
    {
        url = UriHelper.GetAbsoluteUri();
        UriHelper.OnLocationChanged += OnLocationChanged;
    }

    private void OnLocationChanged(object sender, LocationChangedEventArgs e)
    {
        url = newUriAbsolute;
    }

    public void Dispose()
    {
        UriHelper.OnLocationChanged -= OnLocationChanged;
    }
}

I used the same approach used in the NavLink component in the Blazor repository, but it did not work. Any ideas?.

Carlos L.

View more on Stack Overflow

dani herrera · Accepted Answer · 11/25/2019 7:46:56 AM

Use Uri property from NavigationManager class.

How it works

Get it from injection before to use it on .razor pages:

@inject NavigationManager MyNavigationManager

Or like this on .cs if you prefer "code-behind" experience:

using Microsoft.AspNetCore.Components;
...
[Inject] 
public NavigationManager MyNavigationManager {get; set;}

Sample

@page "/navigate"
@inject NavigationManager MyNavigationManager

<h1>Current url</h1>

<p>@(MyNavigationManager.Uri)</p>

More about navigation (NavigateTo, BaseUri, ToAbsoluteUri, ToBaseRelativePath, ... ) at: URI and navigation state helpers

NavigationManager cheatsheet

MyNavigationManager.Uri
#> https://localhost:5001/counter/3?q=hi

MyNavigationManager.BaseUri`
#> https://localhost:5001/

MyNavigationManager.NavigateTo("http://new location")
#> Navigates to new location

MyNavigationManager.LocationChanged
#> An event that fires when the navigation location has changed.

MyNavigationManager.ToAbsoluteUri("pepe")
#> https://localhost:5001/pepe

MyNavigationManager.ToBaseRelativePath( MyNavigationManager.BaseUri)
#> counter/3?q=hi

Helper: AddQueryParm( "q2", "bye" )
#> https://localhost:5001/counter/3?q=hi&q2=bye

Helper: GetQueryParm( "q" )
#> hi

Helpers code:

@code {

[Parameter]
public string Id { get; set; }

// blazor: add parm to url
string AddQueryParm(string parmName, string parmValue)
{
    var uriBuilder = new UriBuilder(MyNavigationManager.Uri);
    var q = System.Web.HttpUtility.ParseQueryString(uriBuilder.Query);
    q[parmName] = parmValue;
    uriBuilder.Query = q.ToString();
    var newUrl = uriBuilder.ToString();
    return newUrl;
}

// blazor: get query parm from url
string GetQueryParm(string parmName)
{
    var uriBuilder = new UriBuilder(MyNavigationManager.Uri);
    var q = System.Web.HttpUtility.ParseQueryString(uriBuilder.Query);
    return q[parmName] ?? "";
}

}

Get current Url in a Blazor component

Question

Fastest Entity Framework Extensions

Popular Answer

How it works

Sample

NavigationManager cheatsheet

Performance

Expression Evaluator