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wpfvisual-studioxaml
Davecz
Davecz

Reputation: 1221

WPF x:Reference thow Object reference not set to an instance of an object

I am developing an application in WPF and from some reason Visual studio display in error window this exception: Object reference not set to an instance of an object

When I was building application this errors are still visible, but I application works correct

this is a my XAML:

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="auto" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>

    <StackPanel Grid.Row="0" Grid.Column="0" Margin="5"
                HorizontalAlignment="Stretch" VerticalAlignment="Top" Orientation="Vertical">
        <CheckBox Name="cbPersonType" Content="Person Type" IsChecked="{Binding Path=IsPersonTypeVisible, Mode=TwoWay}" />
    </StackPanel>

    <StackPanel Grid.Row="0" Grid.Column="1" Margin="5"
                HorizontalAlignment="Stretch" VerticalAlignment="Top" Orientation="Vertical">
        <DataGrid Name="dgPersons">
            <DataGrid.Columns>
                <DataGridTextColumn Width="*" Header="Person Type"
                                    Visibility="{Binding Path=IsChecked, Source={x:Reference Name=cbPersonType}, Converter={StaticResource BooleanToVisibilityConverter}}"
                                        />
            </DataGrid.Columns>
        </DataGrid>
    </StackPanel>
</Grid>

this exception is on DataGridTextColumn. Does some one know why and what is this error?

Upvotes: 0

Views: 1040

Answers (2)

Demarsch
Demarsch

Reputation: 1479

I would suggest to replace Source={x:Reference Name=cbPersonType} with ElementName=cbPersonType. This works fine both in design and runtime modes

Upvotes: -1

Larry G
Larry G

Reputation: 43

This is just a theory from my part trying to explain the errormessage.

Right now I'm struggling with a similar case. However, I have my checkbox in a contextmenu displaying the columns in a datagrid. The user can check the columns he/she wants to see in the datagrid.

Problem is the checkboxes seem not to be initlized until the user actually right-click to open the contextmenu. Until then the datagrid just shows empty rows with no columns at all.

It seems the x:Reference does not kick in until the checkboxes are loaded in the contextmenu.

A simplified XAML of the contextmenu and datagrid is below.

<DataGrid ItemsSource="{Binding OrderCollection}" AutoGenerateColumns="False"  IsReadOnly="True" >
    <DataGrid.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Columnsetup">
                <CheckBox x:Name="chkHeadOrderNo" Content="Ordernumber" IsChecked="{Binding columnVisibilityHeadOrderNo}"/>
            </MenuItem>
        </ContextMenu>
    </DataGrid.ContextMenu>
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding OrderNo}" Header="Ordernumber" 
                            Visibility="{Binding Source={x:Reference chkHeadOrderNo}, Path=IsChecked, Converter={StaticResource convertVisibility}}"/>
    </DataGrid.Columns>
</DataGrid>

Upvotes: 2

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