RZ10012 error when uses 'InputSelect' at blazor with VSCODE

Question

 @page "/Add_book"  
@using Microsoft.Extensions.Logging  
@using Microsoft.AspNetCore.Components.Forms  
  
<ul>  
        <li>  
            <label for = "input_booth"> C </label>  
            <input id = "input_booth" @bind = "Adding_Booth" />  
        </li>  
        <li>  
            <label for = "input_author"> A </label>  
            <input id = "input_author" @bind = "Adding_Author" />  
        </li>  
        <li>  
            <label for = "input_couple">C </label>   
            <input id = "input_couple" @bind =  "Adding_Couple" />  
        </li>  
        <li>  
            <label for = "input_age"> D </label>  
            <select id = "input_age" @bind = "Adding_Age">  
                <option value = "all">1 </option>  
                <option value = "fifteen">15</option>  
                <option value = "ninteen">19</option>  
            </select>  
        </li>  
    </ul>  

versions are all latest.
한국말로도 질문드립니다. 현재 VSCODE로 블레이저 코딩중인데 InputSelect를 쓰면 RZ10012 에러가 뜹니다. 버전은 다 최신버전입니다.