Issue—Blazor ValueChanged event did not fire with built-in input elements

Yes, this is a known issue in Blazor. You can track the issue link in the ValueChanged event not fired thread.

The following code snippet will work. You have to update the model manually because handling the ValueChanged event does not let you use the @bind-Value we need to use ValueExpression instead of @bind-Value.

<EditForm Model="person">
    <DataAnnotationsValidator />
    <div class="form-group">
        <label for="name">Name</label>
        <InputText ValueChanged="@ValueChange" Value="@person.FirstName" ValueExpressions= "@( () => @person.FirstName )" Class="form-control" Id="name" />
    </div>
</EditForm>

@code { 
    Person person = new Person();
    public void ValueChange()
    {
        Console.WriteLine(person.FirstName);
    }
}

Instead, you can also use the OnValidSubmit form event to get and process the value.

<EditForm Model="person" OnValidSubmit="@ValueChange">
  <DataAnnotationsValidator />
   <div class="form-group">
     <label for="name">Name</label>
     <InputText @bind-Value="@person.FirstName" Class="form-control" Id="name" />
   </div>
</EditForm>

@code { 
    Person person = new Person();
    public void ValueChange()
    {
        Console.WriteLine(person.FirstName);
    }
}