Let's configure our Program.cs class by add this configuration:

builder.Services.Configure<CookiePolicyOptions>(options =>
{
    // This lambda determines whether user consent for non-essential 
    // cookies is needed for a given request.
    options.CheckConsentNeeded = context => true;

    options.MinimumSameSitePolicy = SameSiteMode.None;
});

Add following code in your Program class:

app.UseCookiePolicy();

Example:

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.Configure<CookiePolicyOptions>(options =>
{
    // This lambda determines whether user consent for non-essential 
    // cookies is needed for a given request.
    options.CheckConsentNeeded = context => true;

    options.MinimumSameSitePolicy = SameSiteMode.None;
});

var app = builder.Build();

if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();

app.UseRouting();

app.UseAuthorization();

app.MapRazorPages();

app.Run();

Add a new Razor page in the Shared folder with the name: `_CookieConsentPartial.cshtml' and add following code in this new page:

@using Microsoft.AspNetCore.Http.Features

@{
    var consentFeature = Context.Features.Get<ITrackingConsentFeature>();
    var showBanner = !consentFeature?.CanTrack ?? false;
    var cookieString = consentFeature?.CreateConsentCookie();
}

@if (showBanner)
{
    <div id="cookieConsent" class="alert alert-info alert-dismissible fade show" role="alert">
        Use this space to summarize your privacy and cookie use policy. <a asp-page="/Privacy">Learn More</a>.
        <button type="button" class="accept-policy close btn btn-outline-primary" data-dismiss="alert" aria-label="Close" data-cookie-string="@cookieString">
            <span aria-hidden="true">Accept</span>
        </button>
    </div>
    <script>
        (function () {
            var button = document.querySelector("#cookieConsent button[data-cookie-string]");
            button.addEventListener("click", function (event) {
                document.cookie = button.dataset.cookieString;
            }, false);
        })();
    </script>
}

Now add the partial tag-helper in your `_Layout.cshtml' page:

<div class="container">
  <partial name="_CookieConsentPartial" />
  <main role="main" class="pb-3">@RenderBody()</main>
</div>

You can place this partial tag-helper anywhere you want in your HTML code.

If you run your web application you should see something like this:

cookie consent example

If you click Accept then you'll see the cookie message disappear. Refresh your page and you'll see that the message doesn't come back.