DataGrid dgr = new DataGrid()
            {               
                DataContext = ds.Tables[0],
                ItemsSource = ds.Tables[0].DefaultView,
                AutoGenerateColumns = false
            };

void cmmGrid_CanExecute(object sender, CanExecuteRoutedEventArgs e)
   {
      if(Grid.IsValid)
        {
           e.CanExecute = true;
        }
      else
        {
            e.CanExecute = false;
        }
   }

foreach (DataRow row in dgr.Items)
            {
                //
            }

foreach (DataRowView row in dgr.Items)
            {
                //
            }

Binding bind = new Binding("summa") { Mode = BindingMode.TwoWay, Converter = new myConverterDecimalString(), ConverterParameter = "{0:N0}", ValidatesOnDataErrors = true };
bind.ValidationRules.Add(new AllDecimalRule(0, 999999999999));
Style stEdit = new Style(typeof(TextBox));
stEdit.Setters.Add(new Setter(TextBox.MaxLengthProperty, 15));
stEdit.Setters.Add(new Setter(TextBox.TextAlignmentProperty, TextAlignment.Right));
Style st = new Style(typeof(TextBlock));
st.Setters.Add(new Setter(TextBlock.TextAlignmentProperty, TextAlignment.Right));
dgr.Columns.Add(new DataGridTextColumn()
   {
      Header = "summa",
      EditingElementStyle = stEdit,
      ElementStyle = st,
      Binding = bind,
      MinWidth = 110.0,
      MaxWidth = 110.0
   });

 bool DataGridIsValid()
        {
            bool _value = true;

            for (byte b =  0 ; b < dgr.Items.Count; b++)
            {
                foreach (DataGridColumn col in dgr.Columns)
                {
                    if (Validation.GetHasError(col.GetCellContent(dgr.Items[b])))
                    {
                        _value = false;
                    }
                }
            }

            return _value;
        }

void cmmGrid_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            switch ((myEnumButton)e.Parameter)
            { 
                case myEnumButton.save:
                    e.CanExecute = DataGridIsValid();
                    break;                    
                case myEnumButton.refresh:
                case myEnumButton.undo:
                    e.CanExecute = true;
                    break;
            }            
        }