@page "/"
<h1>Hello, world!</h1>
<p>@text</p>
<input value="@text" @oninput="onin"/>
@code
{
public string text;
public void onin(ChangeEventArgs args)
{
var data = args.Value.ToString().Replace("-", "");
var groups = data.Select((c, index) => new {c, index})
.GroupBy(x => x.index/4)
.Select(group => group.Select(elem => elem.c))
.Select(chars => new string(chars.ToArray()));
text = string.Join('-', groups);
}
}