Getting the boolean value of a CheckBox cell in WPF - wpf

Question

I have a DataGrid that has a Checkbox in every first cell of a row. I want to loop through my DataGrid rows and get the rows if the Checkbox in that cell is checked.
This is my code in checking the DataGrid:
Edited based on Ilan's answer:
Private Sub ApproveBtn_Clicked(sender As Object, e As RoutedEventArgs)
For i As Integer = 0 To TimeSheetAppDGrid.Items.Count - 1
TimeSheetAppDGrid.SelectedItem = TimeSheetAppDGrid.Items(i)
Dim row As Row = DirectCast(TimeSheetAppDGrid.SelectedItems(0), Row)
Dim mycheckbox = TryCast(TimeSheetAppDGrid.Columns(0).GetCellContent(TimeSheetAppDGrid.Items(i)), ContentPresenter)
If mycheckbox Is Nothing Then
Return
End If
Dim checkBox = GetAllVisualChildren(mycheckbox).OfType(Of CheckBox)().FirstOrDefault(Function(box) box.Name = "chkSelectAll")
If checkBox Is Nothing Then
Return
End If
Dim isChecked = checkBox.Checked
If isChecked = True Then
MsgBox(row.Mark)
End If
Next
End Sub
The code below doesn't seem to be accepted by VB.NET causing the compilation error that says "Value of type 'FrameworkElement' cannot be converted to 'CheckBox'." After searching the web, almost all of the answers have this code in it but in C# so I converted it:
Dim mycheckbox As CheckBox = TryCast(TimeSheetAppDGrid.Columns(0).GetCellContent(TimeSheetAppDGrid.SelectedItems(0)), CheckBox)
This link is where I got the code. Below is the original line of code from C#:
CheckBox mycheckbox = myGrid.Columns[5].GetCellContent(myGrid.Items[i]) as CheckBox;
This is my xaml for the DataGrid:
<DataGrid Name ="TimeSheetAppDGrid" Margin="16,200,48,0" CanUserSortColumns="False" CanUserReorderColumns="False" CanUserAddRows="False" AutoGenerateColumns="False" SelectionUnit="FullRow"
materialDesign:DataGridAssist.CellPadding="13 8 8 8" materialDesign:DataGridAssist.ColumnHeaderPadding="8" IsReadOnly="True" SelectionMode="Single" >
<DataGrid.Resources>
<Style TargetType="{x:Type DataGridRow}" BasedOn="{StaticResource MaterialDesignDataGridRow}">
<EventSetter Event="MouseDoubleClick" Handler="Row_DoubleClick"/>
</Style>
</DataGrid.Resources>
<DataGrid.Columns>
<DataGridTemplateColumn>
<DataGridTemplateColumn.Header>
<CheckBox Name="AllChkBox" />
</DataGridTemplateColumn.Header>
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<CheckBox Name="chkSelectAll" Margin="3.5 0 0 0"
IsChecked="{Binding IsChecked, ElementName=AllChkBox,
Mode=OneWay}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<DataGridTextColumn Binding="{Binding Path=Mark}" Header="Mark" Width="120" MaxWidth="120"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnEditingStyle}"/>
<materialDesign:MaterialDataGridTextColumn Binding="{Binding Path=ProjectCode}" Header="Project Code" Width="130" MaxWidth="130"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnPopupEditingStyle}"/>
<materialDesign:MaterialDataGridTextColumn Binding="{Binding Path=Project}" Header="Project" Width="250" MaxWidth="250"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnPopupEditingStyle}"/>
<materialDesign:MaterialDataGridTextColumn Binding="{Binding Path=PM}" Header="Project Manager" Width="230" MaxWidth="230"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnPopupEditingStyle}"/>
<materialDesign:MaterialDataGridTextColumn Binding="{Binding Path=Activity}" Header="Activity" Width="600" MaxWidth="600"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnPopupEditingStyle}"/>
<materialDesign:MaterialDataGridTextColumn Binding="{Binding Path=Today}" Header="Date" Width="200" MaxWidth="200"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnPopupEditingStyle}"/>
<materialDesign:MaterialDataGridTextColumn Binding="{Binding Path=Regular}" Header="Regular" Width="130" MaxWidth="130"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnPopupEditingStyle}"/>
<materialDesign:MaterialDataGridTextColumn Binding="{Binding Path=Overtime}" Header="Overtime" Width="130" MaxWidth="130"
EditingElementStyle="{StaticResource MaterialDesignDataGridTextColumnPopupEditingStyle}">
<DataGridTextColumn.HeaderStyle>
<Style TargetType="{x:Type DataGridColumnHeader}" BasedOn="{StaticResource MaterialDesignDataGridColumnHeader}">
<Setter Property="HorizontalAlignment" Value="Left" />
</Style>
</DataGridTextColumn.HeaderStyle>
<DataGridTextColumn.ElementStyle>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="HorizontalAlignment" Value="Left" />
</Style>
</DataGridTextColumn.ElementStyle>
</materialDesign:MaterialDataGridTextColumn>
</DataGrid.Columns>
<DataGrid.CellStyle>
<Style TargetType="{x:Type DataGridCell}" BasedOn="{StaticResource MaterialDesignDataGridCell}">
<Setter Property="BorderThickness" Value="0"/>
</Style>
</DataGrid.CellStyle>
</DataGrid>
Any suggestions?

Answer 1

You have to take look at the visual tree generated using Snoop, so that your cast works properly.
Simplest approach is to keep updating a Dictionary<int, DataGridRow> upon Checked/Unchecked events of the CheckBox.
Sorry the code is in C#.
XAML :
<CheckBox Name="AllChkBox" Checked="AllChkBox_Checked" Unchecked="AllChkBox_Unchecked" />
<CheckBox Name="chkSelectAll" Margin="3.5 0 0 0"
Checked="chkSelectAll_Checked" Unchecked="chkSelectAll_Unchecked"
IsChecked="{Binding IsChecked, ElementName=AllChkBox, Mode=OneWay}"/>
Code :
Dictionary<int, DataGridRow> rows = new Dictionary<int, DataGridRow>();
private void chkSelectAll_Checked(object sender, RoutedEventArgs e)
{
var cur_item = DGrid.CurrentItem;
int cur_index = DGrid.Items.IndexOf(cur_item);
if (cur_index == -1) // header checkbox is checked
return;
DataGridRow row = (DataGridRow)DGrid.ItemContainerGenerator.ContainerFromItem(cur_item);
rows.Add(DGrid.Items.IndexOf(cur_item), row);
}
private void chkSelectAll_Unchecked(object sender, RoutedEventArgs e)
{
var cur_item = DGrid.CurrentItem;
rows.Remove(DGrid.Items.IndexOf(cur_item));
}
private void AllChkBox_Checked(object sender, RoutedEventArgs e)
{
foreach (var item in DGrid.Items)
{
DataGridRow row = (DataGridRow)DGrid.ItemContainerGenerator.ContainerFromItem(item);
rows.Add(DGrid.Items.IndexOf(item), row);
}
}
private void AllChkBox_Unchecked(object sender, RoutedEventArgs e)
{
rows.Clear();
}

Answer 2

EDIT
ok, here's a more refined way of achieving what you need without having to search the visual tree looking for the checkbox (again in c# but hopefully shouldn't be difficult to translate).
Firstly, i've created a Student class to bind to which implements INotifyPropertyChanged :
public class Student:INotifyPropertyChanged
{
private bool _isChecked;
public bool IsChecked
{
get { return _isChecked; }
set { _isChecked = value;
OnPropertyChanged("IsChecked");
}
}
public string Mark { get; set; }
public string ProjectCode { get; set; }
public string Project { get; set; }
public string PM { get; set; }
public string Activity { get; set; }
public DateTime Today { get; set; }
public string Regular { get; set; }
public string Overtime { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
I then add a row to my data grid with test data :
TimeSheetAppDGrid.ItemsSource = new List<Student>()
{
new Student { ProjectCode="Project1",Mark = "A",Today = DateTime.Today}
};
In the XAML for the data template i've changed the binding to not bind to the header check box but bind to the student IsChecked property and i've added a clicked handler for AllChkBox checkbox in the header cell:
<DataGridTemplateColumn>
<DataGridTemplateColumn.Header>
<CheckBox Click="AllChkBox_OnClick" Name="AllChkBox" />
</DataGridTemplateColumn.Header>
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<CheckBox Name="chkSelectAll" Margin="3.5 0 0 0"
IsChecked="{Binding Path=IsChecked,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
For the AllChkBox clicked handler (AllChkBox_OnClick) i iterate through each data source (i.e. Student) and toggle the IsChecked property to the AllChkBox checked value:
private void AllChkBox_OnClick(object sender, RoutedEventArgs e)
{
foreach (var s in TimeSheetAppDGrid.ItemsSource)
{
Student st = s as Student;
st.IsChecked = (bool) AllChkBox.IsChecked;
}
}
Now each item source (i.e. Student) can be interrogated for their IsChecked property (which is bound to the corresponding checkbox cell) without the need to fish around checking for the checkbox (excuse the pun) i.e.
private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
{
foreach (var source in TimeSheetAppDGrid.ItemsSource)
{
Student st = source as Student;
if (st.IsChecked)
MessageBox.Show("Is Checked");
}
}

Answer 3

in my opinion there is some conceptual error in your adopted solution:
CheckBox mycheckbox = myGrid.Columns[5].GetCellContent(myGrid.Items[i]) as CheckBox;
I've checked it and when we use the DataGridTemplateColumn.CellTemplate, like in your case, the value that is accepted(mycheckbox) is the ContentPresenter because there is the DataTemplate behind the cell(because you are using the DataTemplate). That is why the code is actually isn't working.
The solution that I'm suggesting you is to get the check box object from the ContentPresenter(the code is in C# you will have to convert it to VB), since it is the ContentPresenter's visual child(you can se this in Snoop).
UpdateHere is the GetAllVisualChildren code:
public static class VisualTreeHelperExtensions
{
public static T FindParent<T>(this DependencyObject child) where T : DependencyObject
{
while (true)
{
//get parent item
DependencyObject parentObject = VisualTreeHelper.GetParent(child);
//we've reached the end of the tree
if (parentObject == null) return null;
//check if the parent matches the type we're looking for
T parent = parentObject as T;
if (parent != null)
return parent;
child = parentObject;
}
}
public static List<DependencyObject> GetAllVisualChildren(this DependencyObject parent)
{
var resultedList = new List<DependencyObject>();
var visualQueue = new Queue<DependencyObject>();
visualQueue.Enqueue(parent);
do
{
var depObj = visualQueue.Dequeue();
var childrenCount = VisualTreeHelper.GetChildrenCount(depObj);
for (int i = 0; i < childrenCount; i++)
{
var v = VisualTreeHelper.GetChild(depObj, i);
visualQueue.Enqueue(v);
}
resultedList.Add(depObj);
} while (visualQueue.Count > 0);
resultedList.RemoveAt(0);
return resultedList;
}
}
Do next things in order to import the VisualTreeHelperExtensions class to VB
Create a C# class library as the part of your solution.
Add the VisualTreeHelperExtensions class into a new created project.
Compile your C# class library.
Add the new create(and compiled) class library into your vb.net project as a reference(dll).
Update #3 - changed vb code
Dim mycheckbox = TryCast(TimeSheetAppDGrid.Columns(0).GetCellContent(TimeSheetAppDGrid.Items(0)), ContentPresenter)
If mycheckbox Is Nothing Then
Return
End If
Dim checkBox = mycheckbox.GetAllVisualChildren().OfType(Of CheckBox)().FirstOrDefault(Function(box) box.Name = "chkSelectAll")
If checkBox Is Nothing Then
Return
End If
Dim isChecked = checkBox.IsChecked
If isChecked = True Then
MsgBox("Checked")
End If
VB.net CheckBox example
CheckBox Control WPF In VB.NET.
CheckBox Class in .Net Framework(no any restriction to vb)
Since all that the .net CheckBox has its IsChecked boolean state presenter.
Regards.