PreventDefault on Blazor input

I have a simple application with an input field that should insert a predefined piece of text as you type.

The code I have looks like this:

<input type="text" bind="@PetitionInput" onkeydown="@PetitionHandleKeyDown" />
@functions
{
  private int _petitionCharStep = 0;
  private string _petition = "This is a dummy text";
  public string PetitionInput { get; set; } = string.Empty;
    
  void PetitionHandleKeyDown(UIKeyboardEventArgs arg) {
    PetitionInput += _petition[_petitionCharStep];
    _petitionCharStep++;
    
    Console.WriteLine(PetitionInput);
  }
}

When the input field has focus, and I press a letter on my keyboard, then it should add the first letter from the string _petition to the input. When I press any letter on my keyboard, it should enter the second letter into the input field. And so on.

The problem I have is that it also adds the letter at the end of the input that I pressed on my keyboard. I want to prevent that from happening.

Is there a way to fix this using issue Blazor code only?

I have an online demo here.

You can think a little differently in Blazor.

Rather than using "bind" and preventing the keystroke, you can set the "value" and handle the "oninput" event, like this:

https://blazorfiddle.com/s/otd4ioow

@page "/"
<h1>Start typing something...</h1>
<input type="text" value="@PetitionInput" @oninput="@PetitionHandleKeyDown" />
    
@code {
  private int _petitionCharStep = 0;
  private string _petition = "This is a dummy text";
  public string PetitionInput { get; set; } = string.Empty;
    
  void PetitionHandleKeyDown(ChangeEventArgs arg) {
    PetitionInput = _petition.Substring(0,++_petitionCharStep);
    Console.WriteLine(PetitionInput);
  }
}

I can't imagine why you would want to do this, and there are many extra things you need to do to cover backspaces, arrow keys, tab etc...