private bool ValidateForm()
{
var validationErrors = new List <string>();
FirstName.Validate();
validationErrors.AddRange(FirstName.ErrorMessages);
LastName.Validate();
validationErrors.AddRange(LastName.ErrorMessages);
DateOfBirth.Validate();
validationErrors.AddRange(DateOfBirth.ErrorMessages);
ValidationErrors = new ObservableCollection <string>(validationErrors);
return(FirstName.IsValid && LastName.IsValid && DateOfBirth.IsValid);
}