CookieStore

CookieStore is not available in every browser, so feature-detect before relying on it. When it is missing, fall back to the legacy Cookie service - it works everywhere but only exposes name/value pairs.

@inject Bit.Butil.CookieStore cookieStore

if (await cookieStore.IsSupported())
{
    // safe to use cookieStore
}

Set accepts a CookieStoreItem carrying the full attribute set. Omitted attributes get browser defaults (Path becomes /, SameSite becomes strict in Chromium). Leave Expires null for a session cookie, or set an absolute expiry.

await cookieStore.Set(new CookieStoreItem
{
    Name = "butil-docs",
    Value = "hello",
    SameSite = "lax",
    Expires = DateTimeOffset.UtcNow.AddDays(1),
});

This is where CookieStore earns its keep: Get and GetAll return CookieStoreItem objects with every attribute the browser knows - domain, path, expiry, secure flag, SameSite policy and partitioned state - not just the name and value.

var one = await cookieStore.Get("butil-docs");   // CookieStoreItem? - null when absent

var all = await cookieStore.GetAll();            // CookieStoreItem[]

foreach (var c in all)
{
    // c.Name, c.Value, c.Domain, c.Path, c.Expires, c.Secure, c.SameSite, c.Partitioned
}

Delete removes the named cookie directly - no MaxAge = 0 workaround needed. Deleting a cookie that does not exist is a no-op.

await cookieStore.Delete("butil-docs");

The change event is the one thing document.cookie can never give you. It fires for cookies written by script, by a server's Set-Cookie header, and on expiry - which makes it the way to notice a session cookie dying without polling for it. Each notification carries both halves: cookies written and cookies removed. An overwrite arrives as a delete plus a set, so both lists can be non-empty at once.

private ButilSubscription? subscription;

subscription = await cookieStore.SubscribeChange(change =>
{
    foreach (var c in change.Changed) { /* written or updated */ }
    foreach (var c in change.Deleted) { /* removed or expired */ }
});

if (subscription is null)
{
    // no CookieStore here - document.cookie has no change event to fall back on
}

// later
await subscription.DisposeAsync();