Why my properties in my blazor wasm always become null when i submit the form

This is my code:

From what I can see, I am creating a new instance of the class, binding each attribute to the class in the form, then converting to JSON and printing. What am I missing?

@inject IIdentityService IdentityService;@inject ErrorService ErrorService;<div class=" w-full flex justify-center text-main  "><div class="flex w-full"><div class="w-1/2 flex"><div class="w-full h-[100vh] bg-cover bg-center"                 style="background-image: url('./images/identity/login.jpg')"></div></div><div class="bg-white p-8 w-1/2 rounded-lg pt-[10%] px-[5%]"><EditForm Model="RegisterModel" OnValidSubmit="HandleValidSubmit" FormName="RegisterForm"><DataAnnotationsValidator/><ValidationSummary/><!-- First Name and Last Name --><div class="mb-4 flex justify-between"><InputText                        @bind-Value="FirstName"                        placeholder="First Name"                        class="form-control mt-1 block w-[48%] px-6 py-4 border border-gray-300 rounded-md shadow-sm focus:ring-blue-500 focus:border-blue-500 sm:text-sm"                        required/><ValidationMessage For="@(() => FirstName)"/><InputText                        @bind-Value="LastName"                        placeholder="Last Name"                        class="form-control mt-1 block w-[48%] px-6 py-4 border border-gray-300 rounded-md shadow-sm focus:ring-blue-500 focus:border-blue-500 sm:text-sm"                        required/><ValidationMessage For="@(() => LastName)"/></div><!-- Phone Number --><div class="mb-4"><InputText                        @bind-Value="RegisterModel.PhoneNumber"                        placeholder="Phone Number"                        class="form-control mt-1 block w-full px-6 py-4 border border-gray-300 rounded-md shadow-sm focus:ring-blue-500 focus:border-blue-500 sm:text-sm"                        required/><ValidationMessage For="@(() => RegisterModel.PhoneNumber)"/></div><!-- Email --><div class="mb-4"><InputText                        @bind-Value="RegisterModel.Email"                        type="email"                        placeholder="Email"                        class="form-control mt-1 block w-full px-6 py-4 border border-gray-300 rounded-md shadow-sm focus:ring-blue-500 focus:border-blue-500 sm:text-sm"                        required/><ValidationMessage For="@(() => RegisterModel.Email)"/></div><!-- Password --><div class="mb-4"><InputText                        @bind-Value="RegisterModel.Password"                        type="password"                        placeholder="Password"                        class="form-control mt-1 block w-full px-6 py-4 border border-gray-300 rounded-md shadow-sm focus:ring-blue-500 focus:border-blue-500 sm:text-sm"                        required/><ValidationMessage For="@(() => RegisterModel.Password)"/></div><!-- Register Button --><div><button type="submit"                            class="w-full inline-flex justify-center py-2 px-4 border border-transparent shadow-sm font-medium rounded-sm text-white bg-[#00205c] focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-blue-500 text-xl transition-all ease-out">                        Register</button></div></EditForm><div class="w-full flex justify-between mt-3  "><button class="hover:underline" type="button"><NavLink href="/login">                        Already Have An Account?</NavLink></button><button class="hover:underline " type="submit"><a href="">                        Forgot Password?</a></button></div></div></div></div>@code {    [SupplyParameterFromForm(FormName = "RegisterForm")]    private RegisterFormModel RegisterModel { get; set; } = RegisterFormModel.Empty;    private string FirstName { get; set; } = string.Empty;    private string LastName { get; set; } = string.Empty;    private async Task HandleValidSubmit()    {        RegisterModel.Username = $"{FirstName} {LastName}";        var result = await IdentityService.Register(RegisterModel);        if (result.IsFailure)        {            ErrorService.SetErrorMessage(result.ErrorTypes);        }    }

The Problem is when i bind the form value to the p tag, it still display my input value, but when i send the submit, it become null or i should say default value.

I also check it in the server and try to change the default value of the DTOs in the backend, so i can know when i send, the bind value in my blazor form is empty or null.

What can i do? the @rendermode dont work in blazor wasm or i just missing something

Edit: my problem also happen with all of property not only firstname/lastname

Edit2: My service

public class IdentityService(    IHttpClientFactory factory,    string baseUrl = nameof(IdentityService),    string endpoint = "api/User") : BaseApiService(factory, baseUrl, endpoint), IIdentityService{    public async Task<Result> Register(RegisterFormModel registerModel)    {        var content = SerializeItem(registerModel);        var result = await Client.PostAsJsonAsync($"{Endpoint}/Register", content);        return await HandleResponse(result);    }    public async Task<Result<LoginResponse>> Login(LoginFormModel loginModel)    {        var content = SerializeItem(loginModel);        var result = await Client.PostAsJsonAsync($"{Endpoint}/Login", content);        return await HandleResponse<LoginResponse>(result);    }}    protected static StringContent SerializeItem<TItem>(TItem item)        where TItem : class    {        return new StringContent(JsonSerializer.Serialize(item), Encoding.UTF8, "application/json");    }

My model:

public class RegisterFormModel{    public string? Email { get; set; }    public string? Username { get; set; }    public string? Password { get; set; }    public string? PhoneNumber { get; set; }    public static RegisterFormModel Empty =>        new()        {            Email = default,            Username = default,            Password = default,            PhoneNumber = default,        };}