AllowNullableEnums.razor

public class ApplicationUser : IdentityUser
    {
        public string FirstName { get; set; }

        public string LastName { get; set; }

        [NotMapped]
        public string FullName => $"{LastName}, {FirstName}";

        public DateTime? DateOfBirth { get; set; } = DateTime.Now;

        public Gender? Gender { get; set; }
}

@*<--some form in MudBlazor-->*@
<MudSelect T="Gender?" Label="Select Gender" @bind-Value="@EditedUser.Gender"
                           OffsetY="true">
                    @foreach (Gender? g in Enum.GetValues(typeof(Gender)))
                    {
                        <MudSelectItem Value="@g">@g</MudSelectItem>
                    }
                </MudSelect>

public enum Gender
    {
        Female,
        Male,
        Other
    }