TreeView MVVM, how to get selection? - wpf

Question

I am trying to create a TreeView for my application. This is the first time I am using TreeView with the MVVM structure, by all accounts the binding is working and displaying correctly.
However:
How do I get the selection so I can perform some logic after the user selects something?
I thought that the TextValue property in SubSection class would fire PropertyChanged, but it doesn't, so I am left scratching my head.
This is the most simplified set of code I could make for this question:
Using PropertyChanged setup like this in : ViewModelBase class
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
The VeiwModel:
public class ShiftManagerViewModel : ViewModelBase
{
public ShiftManagerViewModel()
{
Departments = new List<Department>()
{
new Section("Section One"),
new Section("Section Two")
};
}
private List<Section> _sections;
public List<Section> Sections
{
get{return _sections;}
set
{
_sections = value;
NotifyPropertyChanged();
}
}
}
The classes:
public class Section : ViewModelBase
{
public Section(string depname)
{
DepartmentName = depname;
Courses = new List<SubSection>()
{
new SubSection("SubSection One"),
new SubSection("SubSection One")
};
}
private List<SubSection> _courses;
public List<SubSection> Courses
{
get{ return _courses; }
set
{
_courses = value;
NotifyPropertyChanged();
}
}
public string DepartmentName { get; set; }
}
public class SubSection : ViewModelBase
{
public SubSection(string coursename)
{
CourseName = coursename;
}
public string CourseName { get; set; }
private string _vTextValue;
public string TextValue
{
get { return _vTextValue; }
set
{
_vTextValue = value;
NotifyPropertyChanged();
}
}
}
And the XAML:
<Window.Resources>
<HierarchicalDataTemplate ItemsSource="{Binding Courses}" DataType="{x:Type viewModels:Section}">
<Label Content="{Binding DepartmentName}" />
</HierarchicalDataTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding TextValue}" DataType="{x:Type viewModels:SubSection}">
<Label Content="{Binding CourseName}" />
</HierarchicalDataTemplate>
</Window.Resources>
Could someone point me in the right direction?

Answer 1

You could cast the SelectedItem property of the TreeView to a Section or a SubSection or whatever the type of the selected item is:
Section section = treeView1.SelectedItem as Section;
if (section != null)
{
//A Section is selected. Access any of its properties here
string name = section.DepartmentName;
}
else
{
SubSection ss = treeView1.SelectedItem as SubSection;
if(ss != null)
{
string ssName = ss.CourseName;
}
}
Or you could add an IsSelected property to the Section and SubSection types and bind the IsSelected property of the TreeView to it:
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
</Style>
</TreeView.ItemContainerStyle>
Then you get the selected item by iterating through the ItemsSource of the TreeView and look for the item that has the IsSelected source property set to true.