Getting content of checkboxes in xaml.cs in Silverlight - xaml

Question

I am new to silverlight. I am trying to generate a list of checkboxes(with content). The idea is that the user will select some of these checkboxes and will press a button. Then we try to read the content of selected checkboxes for further processing. I don't know how many number of checkboxes will be there and therefore I can't use bindings.
This is the code snippet in the .xaml file.
<StackPanel Grid.Row="21" Grid.Column="1" Margin="5" VerticalAlignment="Center">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<ItemsControl Name="infoPairItems" ItemsSource="{Binding InfoPair}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Grid.Column="0" Name="infoPairSelectBox" IsEnabled="True" IsThreeState="False"
Margin="0,5" FontSize="12" IsChecked="bool"
Content="{Binding Converter={StaticResource infoPairToStringValueConverter}}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</StackPanel>
I am trying to access these checkboxes in the .xaml.cs file like this.
foreach(var infoPairItem in infoPairItems.Items)
{
ContentPresenter container = infoPairItems.ItemContainerGenerator.ContainerFromItem(infoPairItem) as ContentPresenter;
if(container == null)
{
DebugLog.Log("container is null ");
}
DataTemplate dataTemplate = container.ContentTemplate;
CheckBox checkBox = (CheckBox)dataTemplate.LoadContent();
if (checkBox == null)
{
DebugLog.Log("checkBox is null !!!");
return;
}
if (checkBox.IsChecked.HasValue)
{
if (checkBox.IsChecked.Value)
{
DebugLog.Log("checkbox value true");
}
else
{
DebugLog.Log("checkbox value false");
}
}
}
The log 'checkbox value false' is always getting printed for all the checkboxes even when some of them are selected. I tried to use the debugger. It looks like that variable container is getting loaded with the correct value. Either the method LoadContent() is not working or I am using the wrong method.
I apologize beforehand if it is a repeat question. I tried to look into the previous questions on stackoverflow but could not find any answer. Please guide me in correct direction.

Answer 1

I will explain what happens and how to solve:
1.- You are getting the datatemplate not instances of the datatemplate, in case you want to manage the instances you can do by using the Loaded Event to add items to the List to create and update for instance a List.
2.- What makes all of these events a really complex code to manage is easier if you create the following:
2.1 A class for instance that has a bool and a string for the content with INotifyPropertyChanged:
public class InfoSelection : Model
{
Property bool for Selected
Property string for Info, or whatever and the converter
}
2.2 A list with the items you need of the type of that class in the DataContext
public List<InfoSelection> {get;set;}
(If you initialize just once in the constructor for instance, you do not need to implement INotiyPropertyChanged, just clear or removeitems, never reassign)
2.3 In the Xaml binding change to the following:
<CheckBox Grid.Column="0"
Name="infoPairSelectBox"
IsEnabled="True"
IsThreeState="False"
Margin="0,5"
FontSize="12"
IsChecked="{Binding Selected, Mode=TwoWay}"
Content="{Binding Info}"/>

Answer 2

I don't know how many number of checkboxes will be there and therefore I can't use bindings.
Incorrect.
To Visually display two levels of data generically, the use of a ItemsControl with individual DataTemplate`s for the parent items and their child items can be done.
Then to allow for the editing (your deletion operation) one needs to identify who the parent node is from the child nodes, along with getting the state of the checkbox.
That identification requires us to project the initial data into a wrapper class to facilitate binding/identification.
Let me explain.
Say our data displays a top level last name and all first names associated with the last name.
The above simulates a top level checkbox (to delete all) and children checkbox (to delete an individual item) for the following data class retrieved from the database:
public class VectorStrings
{
public int Id { get; set; }
public string LastName { get; set; }
public List<string> FirstNames { get; set; }
}
With simulated data loaded as such:
LastNames = new List<VectorStrings>()
{
new VectorStrings() { Id=9, LastName="Smith", FirstNames = new List<string>() { "Bob", "Victoria" } },
new VectorStrings() { Id=12, LastName="Jones", FirstNames = new List<string>() { "Peter", "Paul", "Mary" } },
};
Now for display I can generically display those items to the above data, but because we need to operate on the child data, we need to project that information into a holding wrapper class.
public class VectorCheckbox
{
public int Id { get; set; }
public int ParentId { get; set; }
public string DisplayName { get; set; }
public List<VectorCheckbox> Children { get; set; }
public object Tag { get; set; } // Same concept as a visual control property 'Tag'
}
so our code to project the original data looks like this:
CheckBoxData =
LastNames.Select(ln => new VectorCheckbox()
{
DisplayName = ln.LastName,
Id = ln.Id,
Tag = ln,
Children = ln.FirstNames.Select((fn, index) => new VectorCheckbox()
{
Id = index,
ParentId = ln.Id,
DisplayName = fn,
Tag = ln.Id // Hold the parent Id for identification
}).ToList()
})
.ToList();
Sweet! Now we just need nested ItemControl classes to display our data:
<ItemsControl ItemsSource="{Binding CheckBoxData}">
<ItemsControl.Resources>
<system:String x:Key="Format">Delete All for ID: '{0}' </system:String>
</ItemsControl.Resources>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Vertical" Margin="10" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Margin="6,0,0,0">
<CheckBox Tag="{Binding Id}" Margin="0,0,0,10" Click="DeleteAll_Click">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Id, StringFormat={StaticResource Format}}"/>
<TextBlock Text="{Binding DisplayName}" Margin="4,0,6,0"/>
<ItemsControl ItemsSource="{Binding Children}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Tag="{Binding Tag}"
Content="{Binding DisplayName}"
Click="DeleteIndividual_Click"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</CheckBox>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
Now in code behind we subscribe to the click events. I use a message box to show that I have identified the right items. For example if one clicks on a delete all check box, it identifies the children and the state of the checkbox, and if I click on a child it identifies its parent and itself.
Parent Click
private void DeleteAll_Click(object sender, RoutedEventArgs e)
{
var cb = sender as CheckBox;
if (cb != null)
{
var id = (int)cb.Tag;
var nameInstance = ViewModel.LastNames.FirstOrDefault(nm => nm.Id == id);
if (nameInstance != null)
MessageBox.Show(string.Format("Delete all for {0} of names {1} (Status {2})",
nameInstance.LastName,
string.Join(",", nameInstance.FirstNames),
((cb.IsChecked ?? false) ? "Checked" : "UnChecked")
));
}
}
Child Click
private void DeleteIndividual_Click(object sender, RoutedEventArgs e)
{
var cb = sender as CheckBox;
if (cb != null)
{
var parentId = (int)cb.Tag; // Parent Id
var nameInstance = ViewModel.LastNames.FirstOrDefault(nm => nm.Id == parentId);
if (nameInstance != null)
MessageBox.Show(string.Format("Delete individual for {0} of name {1} (Status {2})",
nameInstance.LastName,
cb.Content,
((cb.IsChecked ?? false) ? "Checked" : "UnChecked")
));
}
}
So from that I have identified the checkbox state along with the target original items. This code simulates ultimately what you want to do. I leave the actual plumbing of the observable collection remove items up to you. But this gets the idea across.
I recommend that you experiment in WPF then take it to Silverlight, for the concepts are the same, but its easier/faster to test out in WPF.