I have a radcombobox with 2 columns and need the value from the 2nd column. I'm using this code to obtain the value in the dropdownclosed event:
theValue = DirectCast(cboSheen.SelectedValue, System.Data.DataRowView).Row("pctUpcharge")
XAML:
<telerik:RadComboBox x:Name="cboSheen" FontSize="16" Margin="0,8,0,0" Background="#F6F8FA" BorderBrush="#D7D8DD" ItemsSource="{Binding}" Text="{Binding sheen}" TextSearch.TextPath="Sheen" IsEditable="True" Style="{DynamicResource RadComboBoxStyle3}" >
<telerik:RadComboBox.ItemTemplate>
<DataTemplate>
<DataGridRow DataContext="{Binding}" Width="400">
<DataGridRow.Template>
<ControlTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Text="{Binding Sheen}" />
<TextBlock Grid.Column="1" Text="{Binding pctUpcharge}" />
</Grid>
</ControlTemplate>
</DataGridRow.Template>
</DataGridRow>
</DataTemplate>
</telerik:RadComboBox.ItemTemplate>
</telerik:RadComboBox>
This does the job almost 100% of the time but there are times when it bombs out with this error:
System.NullReferenceException: Object reference not set to an instance of an object.
I can immediately reselect the item from the combobox and the code will work OK.
So it appears that this line of code is not stable. Is there a better way to get this value?
Thanks
Related
If I have a table like the one below:
<Grid VerticalAlignment="Top" HorizontalAlignment="Left" ShowGridLines="True" Width="250" Height="100">
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<TextBlock FontSize="20" FontWeight="Bold" Grid.ColumnSpan="3" Grid.Row="0">2005 Products Shipped</TextBlock>
<TextBlock FontSize="12" FontWeight="Bold" Grid.Row="1" Grid.Column="0">Quarter 1</TextBlock>
<TextBlock FontSize="12" FontWeight="Bold" Grid.Row="1" Grid.Column="1">Quarter 2</TextBlock>
<TextBlock FontSize="12" FontWeight="Bold" Grid.Row="1" Grid.Column="2">Quarter 3</TextBlock>
<TextBlock Grid.Row="2" Grid.Column="0">50000</TextBlock>
<TextBlock Grid.Row="2" Grid.Column="1">100000</TextBlock>
<TextBlock Grid.Row="2" Grid.Column="2">150000</TextBlock>
<TextBlock FontSize="16" FontWeight="Bold" Grid.ColumnSpan="3" Grid.Row="3">Total Units: 300000</TextBlock>
</Grid>
Would I be able to populate it in one go using an array.
For example, if I had an Array containing "Row 1", "Row 2" etc. thru 10 would I be able to populate the first column with those values?
I'm not sure I'm doing a great job of explaining. I know I could do each cell individually, but I want it to cycle through and do all at once?
Thanks
Firstly, consider just using a ListBox or ItemsControl, with a DataTemplate. Define the 2 header rows in a separate grid, and stack this one underneath. The catch with this approach is that you need to define fixed-width columns, since each row will be its own Grid (or actually StackPanel is more performant in this scenario):
<ItemsControl ItemsSource="{Binding TheArray}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Width="100" Text="{Binding Col1}" />
<TextBlock Width="100" Text="{Binding Col2}" />
<TextBlock Width="100" Text="{Binding Col3}" />
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Secondly, if you need to use a true Grid, then one approach could be to define a Behavior on your Grid. This Behavior class would define an Items dependency property. The dependency property's "changed" handler could then create the TextBlocks (x of them for each cell where x is the number of columns), add them to the Grid, and assign the Grid.Row and Grid.Column properties (and even add the RowDefinitions if necessary).
<Grid>
<i:Interaction.Behaviors>
<my:GridItemsBehavior Items="{Binding TheArray}" />
</i:Interaction.Behaviors>
</Grid>
I wouldn't necessarily recommend the latter approach, because you lose a lot of the power of XAML by creating UI in code-behind.
How to get ItemsControl display items selected Item textbox text value using MVVM pattern?
<ListBox Margin="0,25,0,0" Grid.Row="3" ItemsSource="{Binding Path=ViewModelSearchResults}" SelectedItem="{Binding Path=SelectedCategoryViewModel, Mode=TwoWay}">
<ItemsControl.ItemTemplate>
<DataTemplate >
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<TextBox Grid.Row="0" Grid.Column="0" Text="{Binding Path=CategoryName}" FontSize="14" FontWeight="Normal" />
<TextBox Grid.Row="0" Grid.Column="1" Text="{Binding Path=CategoryID}" FontSize="14" FontWeight="Normal" Visibility="Hidden" />
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ListBox>
Like getting anything else from Views: bind it! Yes, ItemsControl has SelectedItem but ItemsControl itself doesn't have selection behavior. You should use something like ListBox instead.
You can bind SelectedItem to a property and access the required values through that property.
I'm attempting to bind the Visibility property of a TextBlock that's held within the ItemTemplate for a ListView to the IsSelected property of the TextBlock's parent ListViewItem.
With this markup, the TextBlock is always visible.
<ListView x:Name="ItemListView" ItemsSource="{Binding Path=Accounts}" Margin="60,0,0,10" Grid.Row="1" Grid.Column="0">
<ListView.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100">
</ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="200"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Image Width="100" Height="100" Grid.Column="0"></Image>
<StackPanel Grid.Column="1">
<TextBlock Text="{Binding Path=Account.Name}"
FontSize="24" Margin="5,0,0,0" TextWrapping="Wrap" />
</StackPanel>
<TextBlock Grid.Column="3" VerticalAlignment="Bottom"
Visibility="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=IsSelected, Converter={StaticResource boolConverter}, Mode=OneWay}">
Show More Details...
</TextBlock>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Notes:
1. In case it makes any difference, this is WinRT; a Metro app written in C#.
2. boolConverter is a fairly standard converter appears to work correctly.
Use Mode=FindAncestor:
<TextBlock Grid.Column="3" VerticalAlignment="Bottom"
Visibility="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ListViewItem}, Path=IsSelected, Converter={StaticResource boolConverter}, Mode=OneWay}">
I think that in this case you will have to use ElementName=ItemListView
#Murven 's answer was close. This is what worked for me:
<TextBlock Visibility="{Binding DataContext.IsSelected, ElementName=ItemListView Converter={StaticResource boolConverter}, Mode=OneWay}">
I had to use DataContext.IsSelected to access the context of the ItemListView.
Not sure if there is a better way.
Which of these methods is best?
<Window.Resources>
<sys:Int16 x:Key="MyValue">123</sys:Int16>
</Window.Resources>
<StackPanel>
<!-- method 1 -->
<TextBlock Text="{Binding}" DataContext="{StaticResource MyValue}" />
<!-- method 2 -->
<TextBlock Text="{Binding, Source={StaticResource MyValue}}" />
</StackPanel>
As with many "which is better" questions. I would say that "it depends" on the context.
They both exist because they both can serve a purpose in different contexts. Given only what you have shown above, I would choose Example 2.
When you set the DataContext, however, all of its children will inherit that DataContext. So maybe instead you are using a Button. And within you Button, you want to jazz it up a bit and display the text four times each with a different color. As you can see below, I would then choose Example 1.
Example 1: (note the DataContext is on the button, and the TextBlocks don't need the Source like they do in Example 2)
<Button DataContext="{StaticResource MyValue}" Height="Auto" Width="Auto" HorizontalAlignment="Center" VerticalAlignment="Center">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding}" Foreground="Red" />
<TextBlock Grid.Row="1" Grid.Column="0" Text="{Binding}" Foreground="Blue" />
<TextBlock Grid.Row="0" Grid.Column="1" Text="{Binding}" Foreground="Yellow"/>
<TextBlock Grid.Row="1" Grid.Column="1" Text="{Binding}" Foreground="Green" />
</Grid>
</Button>
Example 2:
<Button Height="Auto" Width="Auto" HorizontalAlignment="Center" VerticalAlignment="Center">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding, Source={StaticResource MyValue}}" Foreground="Red" />
<TextBlock Grid.Row="1" Grid.Column="0" Text="{Binding, Source={StaticResource MyValue}}" Foreground="Blue" />
<TextBlock Grid.Row="0" Grid.Column="1" Text="{Binding, Source={StaticResource MyValue}}" Foreground="Yellow"/>
<TextBlock Grid.Row="1" Grid.Column="1" Text="{Binding, Source={StaticResource MyValue}}" Foreground="Green" />
</Grid>
</Button>
When you're binding to a simple object that only has one representation like an Int16 in your case, you're probably only going to bind and display that value once, and thus option 2 makes most sense.
A good rule of thumb... if you find yourself setting the 'Source' to the same thing more than one binding, you should probably just bind the DataContext of a common parent FrameworkElement.
I would say that if I had to choose between the two, I would go with method 2. DataContext is really more for Databinding an item to a more complex underlying object and eases the databinding of many data values.
Just out of curiosity, why are you doing it this way? Does your code change the value of MyValue at some point? Is there no better way for you to do it for some reason?
The DataContenxt DependencyProperty allows you to easily bind across all of proeprties for a DependencyObject.
The Source DependenceyProperty of a Binding allows you to point that specific binding to the source you want, regardless of the DataContext.
This becomes really helpful when you are doing more complex bindings for ListViews. For instance:
<Window.Resources>
<local:MyConverter x:Key="MyConverter" />
</Window.Resources>
<Grid>
<ComboBox ItemsSource="{Binding Source={StaticResource MyConverter}, Path=DisplayValues}" DataContenxt={Binding ElementName=lvwItems Path=SelectedItem} SelectedItem="{Binding Converter={StaticResource MyConverter}"/>
<ListView Name="lvwItems"......
The above example just shows off that I set the itemssource to a property in the 'MyConverter' called DisplayValues, the datacontext is what I am working with on that combobox though, which is handling the SelectedItem property of the ListView named 'lvwItems'.
Hope this helps.
I have listbox that displays information about list of objects:
<ListBox Grid.Column="0" Height="152" Name="CustomersList" HorizontalAlignment="Stretch">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=Name, Mode=OneWay}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
I would show more detailed information about selected item in another block, but I don't know (and can't find) how to bind selected item to those block data context. I guess it should be something like this:
<Grid Grid.Column="1" DataContext="{Binding Path=ItemSelected, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="150"/>
<ColumnDefinition Width="250"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="Id" VerticalAlignment="Center" />
<TextBox Grid.Row="0" Grid.Column="1" Text="{Binding Path=Id}" VerticalAlignment="Center"/>
<TextBlock Grid.Row="1" Grid.Column="0" Text="Name" VerticalAlignment="Center"/>
<TextBox Grid.Row="1" Grid.Column="1" Text="{Binding Path=Name}" VerticalAlignment="Center"/>
<StackPanel Grid.Row="2" Grid.ColumnSpan="2" Orientation="Horizontal" HorizontalAlignment="Center">
<Button Content="Add new" />
<Button Content="Store changes" />
</StackPanel>
</Grid>
But the problem is that data item to be binded to the grid is not specified anywhere and I don't know how to do that.
Any suggestion would be wellcome.
Thanks!
P.S. I've tried to specify CustomersList.ItemsSource as DataContext for the Grid - this didn't give any result.
You can bind to the SelectedItem property of the ListBox, one way is using ElementName.
<Grid DataContext="{Binding ElementName=CustomersList, Path=SelectedItem}"> </Grid>