Delay validation after typing

[blemidon]

I want to check if the typed username already exists in the database. I've got an async query, but i don't want to check it after every typed character but 1s after typing finished.

Here is what i've got so far:

`
[Reactive]
public string? Username{ get; set; }

[ObservableAsProperty]
public bool IsUsernameExists{ get; }
...
this.WhenAnyValue(x => x.Username)
.Throttle(TimeSpan.FromMilliseconds(1000)
.Select(x => this.UserNameExists.ExecuteAsync(x))
.Select(x => x.Result)
.ToPropertyEx(this, vm => vm.IsUsernameExists);

this.ValidationRule(x => x.Username, x => !this.IsUsernameExists, "Username already exists.");`

The problem is, when Username changed, the validation evaulates IsUsernameExists before it is updated because the delay. So the validation is always 1 character behind typing.
Does anyone know a solution for the problem?

Thanks in advance,
Imre Horvath