Iterate over datagrid rows to get the value of radio column getting Null Exception after 20 rows

dadou 0
Viewed 49

I have an issue with my datagrid when trying to get a value of a cell. Everything working fine until I'm reaching rows #20. I'm getting a null exception. Is it a limit of datagrid rows in iteration? Because in the visual, I can see all the rows.

I didn't have issue in the past with Datagrid but they were not any radiobutton or checkbox column, perhaps an issue with their rendering?

Here's my code:

XAML

<DataGrid x:Name="datagrid_wafer_300" Margin="5" HeadersVisibility="Column" GridLinesVisibility="None">
                        <DataGrid.Columns>
                            <DataGridTextColumn Binding="{Binding ID}" Header="ID" Width="140" IsReadOnly="True" Visibility="Hidden">
                                <DataGridTextColumn.HeaderStyle>
                                    <Style TargetType="{x:Type DataGridColumnHeader}">
                                        <Setter Property="HorizontalAlignment" Value="Stretch"/>
                                        <Setter Property="HorizontalContentAlignment" Value="Center"/>
                                        <Setter Property="FontWeight" Value="Bold" />
                                    </Style>
                                </DataGridTextColumn.HeaderStyle>
                                <DataGridTextColumn.ElementStyle>
                                    <Style>
                                        <Setter Property="TextBlock.TextWrapping" Value="Wrap"/>
                                        <Setter Property="TextBlock.TextAlignment" Value="Center"/>
                                        <Setter Property="TextBlock.Margin" Value="10,0"/>
                                        <Setter Property="TextBlock.VerticalAlignment" Value="Center"/>
                                    </Style>
                                </DataGridTextColumn.ElementStyle>
                            </DataGridTextColumn>
                            <DataGridTemplateColumn x:Name="column_check_300" Width="10" IsReadOnly="True">
                                <DataGridTemplateColumn.CellTemplate>
                                    <DataTemplate>
                                        <RadioButton HorizontalAlignment="Center" VerticalAlignment="Center" GroupName="{Binding Part_Number}"  IsChecked="{Binding IsIncluded}"/>
                                    </DataTemplate>
                                </DataGridTemplateColumn.CellTemplate>
                            </DataGridTemplateColumn>
                            <DataGridTextColumn Binding="{Binding Part_Number}" Header="Part Number" Width="140" IsReadOnly="True">
                                <DataGridTextColumn.HeaderStyle>
                                    <Style TargetType="{x:Type DataGridColumnHeader}">
                                        <Setter Property="HorizontalAlignment" Value="Stretch"/>
                                        <Setter Property="HorizontalContentAlignment" Value="Center"/>
                                        <Setter Property="FontWeight" Value="Bold" />
                                    </Style>
                                </DataGridTextColumn.HeaderStyle>
                                <DataGridTextColumn.ElementStyle>
                                    <Style>
                                        <Setter Property="TextBlock.TextWrapping" Value="Wrap"/>
                                        <Setter Property="TextBlock.TextAlignment" Value="Center"/>
                                        <Setter Property="TextBlock.Margin" Value="10,0"/>
                                        <Setter Property="TextBlock.VerticalAlignment" Value="Center"/>
                                    </Style>
                                </DataGridTextColumn.ElementStyle>
                            </DataGridTextColumn>
                            <DataGridTextColumn Binding="{Binding Description}" Header="Description" Width="*" IsReadOnly="True">
                                <DataGridTextColumn.HeaderStyle>
                                    <Style TargetType="{x:Type DataGridColumnHeader}">
                                        <Setter Property="HorizontalAlignment" Value="Stretch"/>
                                        <Setter Property="HorizontalContentAlignment" Value="Center"/>
                                        <Setter Property="FontWeight" Value="Bold" />
                                    </Style>
                                </DataGridTextColumn.HeaderStyle>
                                <DataGridTextColumn.ElementStyle>
                                    <Style>
                                        <Setter Property="TextBlock.TextWrapping" Value="Wrap"/>
                                        <Setter Property="TextBlock.TextAlignment" Value="Center"/>
                                        <Setter Property="TextBlock.Margin" Value="10,0"/>
                                        <Setter Property="TextBlock.VerticalAlignment" Value="Center"/>
                                    </Style>
                                </DataGridTextColumn.ElementStyle>
                            </DataGridTextColumn>
                            <DataGridTemplateColumn x:Name="column_exclude_300" Header="Exclude?" Width="60" IsReadOnly="True">
                                <DataGridTemplateColumn.HeaderStyle>
                                    <Style TargetType="{x:Type DataGridColumnHeader}">
                                        <Setter Property="HorizontalAlignment" Value="Stretch"/>
                                        <Setter Property="HorizontalContentAlignment" Value="Center"/>
                                        <Setter Property="VerticalAlignment" Value="Center"/>
                                        <Setter Property="FontWeight" Value="Bold" />
                                    </Style>
                                </DataGridTemplateColumn.HeaderStyle>
                                <DataGridTemplateColumn.CellTemplate>
                                    <DataTemplate>
                                        <RadioButton HorizontalAlignment="Center" VerticalAlignment="Center" GroupName="{Binding Part_Number}" IsChecked="{Binding IsIncluded}"/>
                                    </DataTemplate>
                                </DataGridTemplateColumn.CellTemplate>
                            </DataGridTemplateColumn>
                        </DataGrid.Columns>
                    </DataGrid>

C# code:

private void Clear_Datagrid()
{
        for (int i = 0; i < datagrid_wafer_200.Items.Count; i++)
        {
            var item = datagrid_wafer_200.Items[i];
            FrameworkElement elmtTest = datagrid_wafer_200.Columns[1].GetCellContent(item);
            var radio = FindVisualChild<RadioButton>(elmtTest);
            var wafer = datagrid_wafer_200.Columns[2].GetCellContent(item) as TextBlock;
            FrameworkElement elmtTest1 = datagrid_wafer_200.Columns[4].GetCellContent(item);
            var exclude = FindVisualChild<RadioButton>(elmtTest1);

            radio.IsChecked = false;
            exclude.IsChecked = false;
        }

        for (int i = 0; i < datagrid_wafer_300.Items.Count; i++)
        {
            var item = datagrid_wafer_300.Items[i];
            FrameworkElement elmtTest = datagrid_wafer_300.Columns[1].GetCellContent(item);

            var radio = FindVisualChild<RadioButton>(elmtTest);
            var wafer = datagrid_wafer_300.Columns[2].GetCellContent(item) as TextBlock;
            FrameworkElement elmtTest1 = datagrid_wafer_300.Columns[4].GetCellContent(item);
            var exclude = FindVisualChild<RadioButton>(elmtTest1);

            radio.IsChecked = false;
            exclude.IsChecked = false;
        }
}

Thank you

wpf c#
2 Answers

Is it a limit of datagrid rows in iteration?

It's called UI virtualization and means that the visual containers for the data items are created on a per-need basis.

It's considered a bad practice to acess the visual elements directly but if you really need to do this for one reason or another you should probably turn off the virtualization:

<DataGrid VirtualizingPanel.IsVirtualizing="False" EnableRowVirtualization="False" ... />

The other option is otherwise to bind the IsChecked property of the RadioButton to a property of your data object and looking at this property instead of the one of the RadioButton.

mm80

Your iteration starts from 0 to your list's count. Seems like the list has 19 elements and your loop continues to the 20th element wich is null.

It should be like this:

for (int i = 0; i < datagrid_wafer_200.Items.Count - 1; i++)
{
    // ...
}  
for (int i = 0; i < datagrid_wafer_300.Items.Count - 1; i++)
{
    // ...
}
BouRHooD0
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