Wpf MVVM and editing DatagridCell


Wpf MVVM and editing DatagridCell



In an MVVM project the row of a Datagrid is bound is bound to an object OA and a column of the datagrid is bound to property PB=Code.Value of this object.


Code.Value



Binding="{Binding Code.Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True, ValidatesOnDataErrors=True}"


Binding="{Binding Code.Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True, ValidatesOnDataErrors=True}"



After changing the property PB we do OnPropertyChanged("Code");


OnPropertyChanged("Code");



This seems to work all right, except that when I have edited the value PB in the cell of the datagrid and then click on another control outside the datagrid or on another row of the datagrid or also when I use the enter key, then the setter of property PB is triggered with a blank value "". This is triggered via "external code".


""



I noticed that when I edit the cell a second time, this does not happen ...



The source code of xaml datagrid:


<DataGrid Style="{StaticResource MyDataGrid}" BorderBrush="Black" Width="150"
BorderThickness="1" HorizontalScrollBarVisibility="Hidden" Grid.Row="2" Height="200"
AutoGenerateColumns="False" HorizontalAlignment="Left" ColumnHeaderHeight="24" Margin="4"
VirtualizingPanel.IsVirtualizing="true" VirtualizingPanel.VirtualizationMode="Recycling"
EnableRowVirtualization="True" EnableColumnVirtualization="True" HeadersVisibility="Column"
SelectedItem="{Binding ItemSelection, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
ItemsSource="{Binding ListItems, UpdateSourceTrigger=PropertyChanged, IsAsync=True}"
SelectionMode="Single" SelectionUnit="FullRow" GridLinesVisibility="None" SelectionChanged="Grid_SelectionChanged" >

<DataGrid.Columns>

<DataGridTextColumn CanUserSort="False" CanUserReorder="false" Header="Name" Width="*"
Binding="{Binding Code.Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True, ValidatesOnDataErrors=True}" >
<DataGridTextColumn.CellStyle>
<Style TargetType="DataGridCell" BasedOn="{StaticResource DataGridCellEdit}"/>
</DataGridTextColumn.CellStyle>
<DataGridTextColumn.ElementStyle>
<Style TargetType="{x:Type TextBlock}" BasedOn="{StaticResource dgTextBlockViewLinks}">
<Setter Property="ToolTip" Value="{Binding Code.Tooltip}"/>
<Setter Property="Background" Value="{Binding Code.Background}"/>
<Setter Property="Foreground" Value="{Binding Code.Foreground}"/>
</Style>
</DataGridTextColumn.ElementStyle>
<DataGridTextColumn.EditingElementStyle>
<Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource dgTextBoxEditLeft}">
<Setter Property="MaxLength" Value="20"/>
</Style>
</DataGridTextColumn.EditingElementStyle>
</DataGridTextColumn>

</DataGrid.Columns>

</DataGrid>



Maybe someone has an intuition of what is going on here.
I would very much like to prevent using canceledits and/or commitedits on the cell.





what do you mean triggered via "External Code"
– Muds
Jun 28 at 12:46





What I mean is, that after hitting Enter in the UI the code enters the setter of Code.Value with a blank value but the call stack of VS shows that it comes from External Code. When I hit enter the datagridcell shows the correct value that I entered manually via the UI, but there is a system call that updates this value to a blank value.
– Gerard
Jun 28 at 13:01


Code.Value





Maybe validation failed because datacolumn type doesn't match input type data...
– Maxwell77
Jun 28 at 16:00





either it is validation, or converter or some template that hides actual cell... share your xaml might be a little useful, also do check if source to view update works fine
– Muds
Jun 28 at 16:42





I checked and there is no validation error (also second time it works) and update source to view works fine. Added xaml code.
– Gerard
Jun 29 at 8:29









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