C# WPF How to bind a nested class to nested datagrid in “Datagrid Row-Details”?

Question

How to bind data from nested classs to a nested datagrid? Why nested datagrid unable to read the class? what error i am doing?

public class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public DateTime Birthday { get; set; }
        public Marks myMarks { get; set; }
    }

    public class Marks
    {
        public double English { get; set; }
        public double Maths { get; set; }
        public double Science { get; set; }
    }

Itemsource for main-datagrid "DG_myStudents"

private void Page_Loaded(object sender, RoutedEventArgs e)
{
   List<Student> myStudents = new List<Student>();

    Marks JohnMark = new Marks();
    JohnMark.English = 75;
    JohnMark.Maths = 85;
    JohnMark.Science = 95;

    Marks RichardMark = new Marks();
    RichardMark.English = 70;
    RichardMark.Maths = 80;
    RichardMark.Science = 90;

    Marks SamMark = new Marks();
    SamMark.English = 72;
    SamMark.Maths = 82;
    SamMark.Science = 92;

    myStudents.Add(new Student() { Id = 1, Name = "John Doe", Birthday = new DateTime(1971, 7, 23), myMarks = JohnMark });
    myStudents.Add(new Student() { Id = 2, Name = "Richard Doe", Birthday = new DateTime(1974, 1, 17), myMarks = RichardMark });
    myStudents.Add(new Student() { Id = 3, Name = "Sammy Doe", Birthday = new DateTime(1991, 9, 2), myMarks = SamMark });

    DG_myStudents.ItemsSource = myStudents;
}

and below is my XAML code, Am i doing any error in class structure? Please help me.

<DataGrid x:Name="DG_myStudents" RowDetailsVisibilityMode="Visible">
        <DataGrid.RowDetailsTemplate>
            <DataTemplate>
                <DataGrid x:Name="DG_myMarks" ItemsSource="{Binding myMarks}" />
            </DataTemplate>
        </DataGrid.RowDetailsTemplate>
    </DataGrid>

The nested datagrid "DG_myMarks" is not showing any data. And when i bind "myMarks" to a label tfor just to check any thing happening there, then label is showing "Marks class name" like this "MyNameSpace.myPage+Marks"

Answer 1

Hi, ItemsSource of DataGrid (in RowDetailsTemplate) needs collection (e.g. list). Change your code:

private void Page_Loaded(object sender, RoutedEventArgs e)
{
  List<Student> myStudents = new List<Student>();

  Marks JohnMark = new Marks();
  JohnMark.English = 75;
  JohnMark.Maths = 85;
  JohnMark.Science = 95;

  Marks RichardMark = new Marks();
  RichardMark.English = 70;
  RichardMark.Maths = 80;
  RichardMark.Science = 90;

  Marks SamMark = new Marks();
  SamMark.English = 72;
  SamMark.Maths = 82;
  SamMark.Science = 92;

  Student stud = new Student() { Id = 1, Name = "John Doe", Birthday = new DateTime(1971, 7, 23) };
  stud.myMarks.Add(JohnMark);
  myStudents.Add(stud);
  stud = new Student() { Id = 2, Name = "Richard Doe", Birthday = new DateTime(1974, 1, 17) };
  stud.myMarks.Add(RichardMark);
  myStudents.Add(stud);
  stud = new Student() { Id = 3, Name = "Sammy Doe", Birthday = new DateTime(1991, 9, 2) };
  stud.myMarks.Add(SamMark);
  myStudents.Add(stud);
  DG_myStudents.ItemsSource = myStudents;
}

public class Student
{
  public int Id { get; set; }
  public string Name { get; set; }
  public DateTime Birthday { get; set; }
  public List<Marks> myMarks { get; set; } = new List<Marks>();
}

Answer 2

Welcome to our Microsoft Q&A platform!

I made a example ,you can try it.

 public partial class MainWindow : Window  
    {  
        public MainWindow()  
        {  
            InitializeComponent();  
        }  
  
        private void Window_Loaded(object sender, RoutedEventArgs e)  
        {  
            List<Student> myStudents = new List<Student>();  
  
            Marks JohnMark = new Marks();  
            JohnMark.English = 75;  
            JohnMark.Maths = 85;  
            JohnMark.Science = 95;  
  
            Marks RichardMark = new Marks();  
            RichardMark.English = 70;  
            RichardMark.Maths = 80;  
            RichardMark.Science = 90;  
  
            Marks SamMark = new Marks();  
            SamMark.English = 72;  
            SamMark.Maths = 82;  
            SamMark.Science = 92;  
  
            myStudents.Add(new Student() { Id = 1, Name = "John Doe", Birthday = new DateTime(1971, 7, 23), myMarks = JohnMark });  
            myStudents.Add(new Student() { Id = 2, Name = "Richard Doe", Birthday = new DateTime(1974, 1, 17), myMarks = RichardMark });  
            myStudents.Add(new Student() { Id = 3, Name = "Sammy Doe", Birthday = new DateTime(1991, 9, 2), myMarks = SamMark });  
  
  
            DG_myStudents.ItemsSource = myStudents;  
  
             
        }  
        private void Expander_Expanded(object sender, RoutedEventArgs e)  
        {  
            DataGridRow row = FindVisualParent<DataGridRow>(sender as Expander);  
            row.DetailsVisibility = System.Windows.Visibility.Visible;  
        }  
  
        private void Expander_Collapsed(object sender, RoutedEventArgs e)  
        {  
            DataGridRow row = FindVisualParent<DataGridRow>(sender as Expander);  
            row.DetailsVisibility = System.Windows.Visibility.Collapsed;  
        }  
        
        public T FindVisualParent<T>(DependencyObject child) where T : DependencyObject  
        {  
            DependencyObject parentObject = VisualTreeHelper.GetParent(child);  
            if (parentObject == null) return null;  
            T parent = parentObject as T;  
            if (parent != null)  
                return parent;  
            else  
                return FindVisualParent<T>(parentObject);  
        }  
         
  
        private void DG_myStudents_RowDetailsVisibilityChanged(object sender, DataGridRowDetailsEventArgs e)  
        {  
             
            DataGrid MainDataGrid = sender as DataGrid;  
            var cell = MainDataGrid.CurrentCell;  
           
            Student student = (MainDataGrid.CurrentItem as Student);  
            if (student == null)  
            {  
                return;  
            }  
            List<Marks> MarksList = new List<Marks>();  
            DataGrid DetailsDataGrid = e.DetailsElement as DataGrid;  
  
            MarksList.Add(new Marks() { English = student.myMarks.English, Maths = student.myMarks.Maths, Science = student.myMarks.Science });  
            DetailsDataGrid.ItemsSource = MarksList;  
        }  
  
  
    }  
  
    public class Student  
    {  
        public int Id { get; set; }  
        public string Name { get; set; }  
        public DateTime Birthday { get; set; }  
        public Marks myMarks { get; set; }  
    }  
  
    public class Marks  
    {  
        public double English { get; set; }  
        public double Maths { get; set; }  
        public double Science { get; set; }  
    }  

xaml

  <Grid>  
        <DataGrid x:Name="DG_myStudents" RowDetailsVisibilityMode="Visible" AutoGenerateColumns="False" RowDetailsVisibilityChanged="DG_myStudents_RowDetailsVisibilityChanged" >  
            <DataGrid.Columns>  
                <DataGridTemplateColumn Width="Auto">  
                    <DataGridTemplateColumn.CellTemplate>  
                        <DataTemplate>  
                            <Expander Width="50" Expanded="Expander_Expanded" Collapsed="Expander_Collapsed" IsExpanded="False" />  
                        </DataTemplate>  
                    </DataGridTemplateColumn.CellTemplate>  
                </DataGridTemplateColumn>  
                <DataGridTextColumn Header="Id" Binding="{Binding Id}" CanUserResize="False" Width="Auto"/>  
                <DataGridTextColumn Header="Name" Binding="{Binding Name}" CanUserResize="False" Width="Auto"/>  
                <DataGridTextColumn Header="Birthday" Binding="{Binding Birthday}" CanUserResize="False" Width="Auto"/>  
                 
            </DataGrid.Columns>  
            <DataGrid.RowDetailsTemplate>  
                <DataTemplate>  
                    <DataGrid x:Name="DG_myMarks" IsReadOnly="True" Margin="15,8,8,8"  Width="399" AutoGenerateColumns="False" >  
                        <DataGrid.Columns>  
                            <DataGridTextColumn Header="English" Binding="{Binding English}" Width="Auto"/>  
                            <DataGridTextColumn Header="Maths" Binding="{Binding Maths}" Width="Auto"/>  
                            <DataGridTextColumn Header="Science" Binding="{Binding Science}" Width="Auto"/>  
                        </DataGrid.Columns>  
                    </DataGrid>  
                </DataTemplate>  
            </DataGrid.RowDetailsTemplate>  
        </DataGrid>  
  
    </Grid>  

Thanks.