I have model (ApplicationUser : Identity user) and I want to update several fields, but if I do not create the remaining fields of model (PasswordHash, PhoneNumber and etc.) then null is passed instead.

 <div class="form-floating py-1 col-12">
      <input asp-for="Email" type="text" class="form-control boarder-0 shadow" />
      <label asp-for="Email" class="ms-2"></label>
      <span asp-validation-for="Email" class="text-danger"></span>
  </div>
  <div class="form-floating py-1 col-12">
      <input asp-for="UserName" type="text" class="form-control boarder-0 shadow" />
      <label asp-for="UserName" class="ms-2"></label>
      <span asp-validation-for="UserName" class="text-danger"></span>
  </div>

if (ModelState.IsValid)
 {
     _unitOfWork.ApplicationUser.Update(userObj);
     _unitOfWork.Save();
 }

What is the best way to transfer only these changes, and fill the rest with what already exists and is not transferred from the view?