RadGridView: the master-detail case via datatables in WPF

[Onotole]

Hello

We trying to implement the master-detail WPF app to learn the capabilities of Telerik RadGridView.

It is a simple application which has RadGridView with the following markup:

<telerik:RadGridView ItemsSource="{Binding Persons}" SelectedItem="{Binding Selectedperson, Mode=TwoWay}" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" AutoGenerateColumns="True" telerik:StyleManager.Theme="Windows7">
            <telerik:RadGridView.ChildTableDefinitions>
                <telerik:GridViewTableDefinition>
                </telerik:GridViewTableDefinition>
            </telerik:RadGridView.ChildTableDefinitions>
            <telerik:RadGridView.HierarchyChildTemplate>
                <DataTemplate>
                    <telerik:RadGridView
                            AutoGenerateColumns="True"
                            telerik:StyleManager.Theme="Windows7"
                            ItemsSource="{Binding Details}">
                    </telerik:RadGridView>
                </DataTemplate>
            </telerik:RadGridView.HierarchyChildTemplate>
        </telerik:RadGridView>

Under the hood is view model which is set to DataContext of the main windows where Telerik RadGridView is placed, as follows:

namespace MasterDetailViaDataTables
{
    public partial class MainWindow : Window
    {

        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = new MainViewModel();
        }

Persons and Details are fields of view model which are ObservableCollection of appropriate instances.
PersonDetails.cs:

namespace MasterDetailViaDataTables
{
    public class PersonDetails : BindableBase
    {
        private int _PersonID;
        public int PersonID
        {
            get { return _PersonID; }
            set { this.SetProperty<int>(ref this._PersonID, value); }
        }

        private string address;
        public string Address
        {
            get { return address; }
            set { this.SetProperty<string>(ref this.address, value); }
        }

        private string _Description;
        public string Description
        {
            get { return _Description; }
            set { this.SetProperty<string>(ref this._Description, value); }
        }

        public static ObservableCollection<PersonDetails> GetDetails()
        {
            ObservableCollection<PersonDetails> details = new ObservableCollection<PersonDetails>();
            try
            {
                DataTable table = new DataTable("persondetail");
                DataColumn PersonID = new DataColumn("PersonID", typeof(System.Int64));
                DataColumn Address = new DataColumn("Address", typeof(System.String));
                DataColumn Description = new DataColumn("Description", typeof(System.String));
                table.Columns.Add(PersonID);
                table.Columns.Add(Address);
                table.Columns.Add(Description);

                for (int pID = 1; pID <= 5; pID++)
                {
                    for (int i = 0; i < 2; i++)
                    {
                        DataRow row = table.NewRow();
                        row["PersonID"] = pID;
                        row["Address"] = "Address" + (pID-1).ToString() + " - " + i.ToString();
                        row["Description"] = "Description" + (pID-1).ToString() + " - " + i.ToString();
                        table.Rows.Add(row);
                    }
                }


                details.Clear();

                for (int i = 0; i < table.Rows.Count; ++i)
                    details.Add(new PersonDetails
                    {
                        PersonID = Convert.ToInt32(table.Rows[i][0]),
                        Address = table.Rows[i][1].ToString(),
                        Description = table.Rows[i][2].ToString()
                    });

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            return details;
        }
    }

Person.cs:

public class Person : BindableBase
{
    private int _PersonID;
    private string _FirstName;
    private string _LastName;

    public int PersonID
    {
        get { return _PersonID; }
        set { this.SetProperty<int>(ref this._PersonID, value); }
    }

    public string FirstName
    {
        get { return _FirstName; }
        set { this.SetProperty<string>(ref this._FirstName, value); }
    }

    public string LastName
    {
        get { return _LastName; }
        set { this.SetProperty<string>(ref this._LastName, value); }
    }

    public static ObservableCollection<Person> GetPersons()
    {
        ObservableCollection<Person> persons = new ObservableCollection<Person>();
        try
        {
            DataTable table = new DataTable("person");
            DataColumn id = new DataColumn("PersonID", typeof(System.Int64));
            id.AutoIncrement = true;
            id.AutoIncrementSeed = 1;
            DataColumn FirstName = new DataColumn("FirstName", typeof(System.String));
            DataColumn LastName = new DataColumn("LastName", typeof(System.String));
            table.Columns.Add(id);
            table.Columns.Add(FirstName);
            table.Columns.Add(LastName);

            for (int i = 0; i < 5; i++)
            {
                DataRow row = table.NewRow();
                row["FirstName"] = "FirstName" + i.ToString();
                row["LastName"] = "LastName" + i.ToString();
                table.Rows.Add(row);
            }

            persons.Clear();

            for (int i = 0; i < table.Rows.Count; ++i)
                persons.Add(new Person
                {
                    PersonID = Convert.ToInt32(table.Rows[i][0]),
                    FirstName = table.Rows[i][1].ToString(),
                    LastName = table.Rows[i][2].ToString()
                });



        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);

        }
        return persons;
    }


}

MainViewModel.cs:

public class MainViewModel : BindableBase, INotifyPropertyChanged
{
    public MainViewModel()
    {
        this.Persons = Person.GetPersons();
    }

    private ObservableCollection<Person> personValues;
    public ObservableCollection<Person> Persons
    {
        get { return personValues; }
        set { this.SetProperty<ObservableCollection<Person>>(ref this.personValues, value); }
    }


    private ObservableCollection<PersonDetails> detailsvalues;
    public ObservableCollection<PersonDetails> Details
    {
        get
        {
            if (this.Selectedperson == null)
            {
                return null;
            }
            return this.LoadDetails(this.Selectedperson.PersonID);
        }

    }

    private ObservableCollection<PersonDetails> LoadDetails(int personID)
    {
        ObservableCollection<PersonDetails> details = new ObservableCollection<PersonDetails>();
        foreach (PersonDetails detail in PersonDetails.GetDetails().Where(item => item.PersonID == personID))
        {
            details.Add(detail);
        }
        return details;
    }

    private Person selectedPersonValue;
    public Person Selectedperson
    {
        get { return selectedPersonValue; }
        set
        {
            this.SetProperty<Person>(ref this.selectedPersonValue, value);
            this.RaiseNotification("Details");
        }
    }

}

We can't get working hierarchical RadGridView. When we trying to expand the parent row, we see the following in the Output window:
System.Windows.Data Error: 40 : BindingExpression path error: 'Details' property not found on 'object' ''Person' (HashCode=43402647)'.
BindingExpression:Path=Details; DataItem='Person' (HashCode=43402647); target element is 'RadGridView' (Name=''); target property is 'ItemsSource' (type 'Object')
We can't figure out what is wrong here, can you help us?

[Rossen Hristov]

Hi,

The DataContext of each child grid is the parent data item, i.e. Person. Since Person does not have a Details property your Binding fails. Each Person should have many PersonDetails, hence the Person class should have an IEnumerable<PersonDetail> property which the child grid can bind to.

This is how one-to-many relationships are established.

Regards,
Rossen Hristov
Telerik

[Onotole]

Thanks!