validation fails wpf mvvm

learning wpf with mvvm (using EF as ORM).

In my view model i have the property:

//---------------ClientNew
        public const string ClientNewConst = "ClientNew";
        private TBL_CLIENT _clientNew = new TBL_CLIENT();
        public TBL_CLIENT ClientNew
        {
            get
            {
                return _clientNew;
            }

            set
            {
                if (_clientNew == value)
                {
                    return;
                }

                var oldVal开发者_StackOverflowue = _clientNew;
                _clientNew = value;

                // Update bindings, no broadcast
                RaisePropertyChanged(ClientNewConst);
            }
        }

where TBL_CLIENT - is an entittyobject that mirrors TBL_CLIENT table in DB

now, in my VIEW i bind bunch of textboxes like this(example only for client's first name):

<TextBox  Style="{StaticResource ResourceKey=entryFormTextBox}"
                                      Text="{Binding ClientNew.CLIENT_FIRST_NAME, 
                                ValidatesOnDataErrors=True,
                                NotifyOnValidationError=true,
                                ValidatesOnExceptions=True, 
                                UpdateSourceTrigger=LostFocus}"
                                      Grid.Column="1"
                                      Grid.Row="1" />

I tried to use different triggers for updatesource.. still teh validation does not work.

oh, i do have implemented idataerrorinfo interface in my viewmodel (but it never hits it..)

#region IDataErrorInfo Members

        string IDataErrorInfo.Error
        {
            get { throw new NotImplementedException(); }
        }

        string IDataErrorInfo.this[string columnName]
        {
            get 
            {
                if (string.IsNullOrEmpty("ClientNew.CLIENT_FIRST_NAME"))
                {
                   return "Client Name is required";                    
                }
                return null;
            }
        }

        #endregion

so, question.. how can i implement the simple as possible validation using idataerrorinfo for my case, where i don't have the separate property defined in ModelView for each of the entity object, but the property takes the whole entity object?

thanks in advance, Alex

You might have a look at the BookLibrary sample application of the WPF Application Framework (WAF). It defines the validation rules directly at the entity. Please have a look at "BookLibrary.Domain / Book.cs".