visibility of form sections based on selected index of DataGrid

[Michael J Eber]

We are writing a Silverlight 4.0 application which is actually a conversion of ASP to this application. In one block of forms we have a datagrid at the top of the form. The remainder of the form (each grouped in sections) can only be visible when the datagrid's selected index is > 0. So I know I have to bind the Visibility attribute and I know I have to use a BooleanToVisibilityConverter. What I'm not sure about is that I cannot seem to find just the right statement to get addressability to the datagrid and its' properties leastwise how to do the comparison. I'm thinking I may have to write my own Converter to do the comparison logic but I still have to know how to define the datagrid as the object being passed to the converter. Any help would be greatly appreciated!!! Thanks much, Michael

[Mark Salsbery]

How about a IndexGreaterThanZeroToVisibilityConverter...

public class IndexGreaterThanZeroToVisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return ((int)value > 0) ? Visibility.Visible : Visibility.Collapsed;
    }
    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

(Note: ListBox used here for simplicity...works the same with a DataGrid)

<UserControl.Resources>
    <local:IndexGreaterThanZeroToVisibilityConverter x:Key="IndexGreaterThanZeroToVisibilityConverter" />
</UserControl.Resources>

<Grid x:Name="LayoutRoot" Background="White">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="\*" />
    </Grid.RowDefinitions>
    <ListBox Name="listBox1" Grid.Row="0" Height="100" >
        <ListBoxItem Content="Item 1" />
        <ListBoxItem Content="Item 2" />
        <ListBoxItem Content="Item 3" />
    </ListBox>
    <Grid Grid.Row="1" **Visibility="{Binding ElementName=listBox1, Path=SelectedIndex, Mode=OneWay, Converter={StaticResource IndexGreaterThanZeroToVisibilityConverter}}"** >
        <TextBlock Text="This area is visibile!" FontSize="20" HorizontalAlignment="Center" VerticalAlignment="Center" />
    </Grid>
</Grid>

Mark Salsbery Microsoft MVP - Visual C++ :java:

modified on Thursday, May 19, 2011 11:43 PM

[Michael J Eber]

Hey Mark! You're okay for a C++ guy. :laugh: So I implemented my convert. check Then I implemented the binding. check Added the namespace for local. check Then did local: my converter was visible and got it set with a key. check Ran the solution and got this error at compile time. Error 1 The tag 'DataGridVisibilityConverter' does not exist in XML namespace 'clr-namespace:CNRPGlobal.Converters; assembly=GlobalLibraryDefinitions'. So how is it I can type local: and see my class library. Yet when I compile XAML cannot? I confirmed it is public. Here is a snippet of what I've got:

xmlns:local="clr-namespace:CNRPGlobal.Converters; assembly=GlobalLibraryDefinitions"
xmlns:sys="clr-namespace:System;assembly=mscorlib">

<UserControl.Resources>
    <ResourceDictionary x:Key="styles" Source="/GlobalLibraryDefinitions;component/Themes/Generic.xaml" />
    <local:DataGridVisibilityConverter x:Key="VisibilityConverter" />
</UserControl.Resources>

And the consumption of the converter:

                <cnrp:FormSection x:Name="designSection" Title="Design Section" DataContext="{Binding CurrentDesign, Mode=TwoWay}"
                                  Visibility="{Binding ElementName=dgDesigns, Path=SelectedIndex, Mode=OneWay, Converter={StaticResource VisibilityConverter}}">

[Mark Salsbery]

From what you've shown I can' see the problem. Try a rebuild? The namespace and assembly are correct and you have a reference to that assembly? Also, "local" maybe not a good name for a namespace in a separate assembly :)

Mark Salsbery Microsoft MVP - Visual C++ :java:

[Michael J Eber]

Mark, OMG -- the initial problem was I had a space between the namespace and the assembly name But now I'm getting a runtime error Local values are not allowed in resource dictionary with Source set [Line: 14 Position: 46] It is pointing at my styles object! X|

modified on Friday, May 20, 2011 2:15 PM

[Mark Salsbery]

Patterns are for programmers....the compiler doesn't know anything about MVVM. :) If there's a class called DataGridVisibilityConverter in a namespace CNRPGlobal.Converters in an assembly GlobalLibraryDefinitions then it should work.

Mark Salsbery Microsoft MVP - Visual C++ :java:

[Mark Salsbery]

Try a USerControl from scratch, totally stripped down..does this compile??

<UserControl x:Class="SilverlightTester.ConverterTestPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:gspace="clr-namespace:CNRPGlobal.Converters;assembly=GlobalLibraryDefinitions"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">

<UserControl.Resources>
    <gspace:DataGridVisibilityConverter x:Key="VisibilityConverter" />
</UserControl.Resources>

<Grid x:Name="LayoutRoot" Background="White">
</Grid>

</UserControl>

Mark Salsbery Microsoft MVP - Visual C++ :java:

modified on Friday, May 20, 2011 2:25 PM

[Michael J Eber]

got past the compile issue. It was the space just before assembly:!!! Now I just have to figure out my runtime issues with the resource dictionary. X| It doesn't like having that resource along with a ResourceDictionary entry! WTF???

[Mark Salsbery]

Hmm CodeProject editor must have added the space - there's no space in my code here! :)

Mark Salsbery Microsoft MVP - Visual C++ :java:

[Michael J Eber]

WOOHOO!!! Got a clean compile AND a good XAML parse. Here is the final results I had to implement!

xmlns:g="clr-namespace:CNRPGlobal.Converters;assembly=GlobalLibraryDefinitions"
xmlns:sys="clr-namespace:System;assembly=mscorlib">

<UserControl.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="/GlobalLibraryDefinitions;component/Themes/Generic.xaml" />
            <ResourceDictionary>
                <g:DataGridVisibilityConverter x:Key="VisibilityConverter" />
            </ResourceDictionary>
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>

</UserControl.Resources>

[Mark Salsbery]

Awesome! Was just about to send this...

<UserControl.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="/GlobalLibraryDefinitions;component/Themes/Generic.xaml" />
        </ResourceDictionary.MergedDictionaries>
        <converters:IndexGreaterThanZeroToVisibilityConverter x:Key="IndexGreaterThanZeroToVisibilityConverter" />
    </ResourceDictionary>
</UserControl.Resources>

Mark Salsbery Microsoft MVP - Visual C++ :java: