Trouble with a drag and drop TreeView and Gridview

[Goldoni]

Good morning,

I would like to use a TreeView  that's can drag and drop in  a GridView

I make the TreeView but when a want to drag and drop i have a probleme the null Exception, after   4 days i can't see the problem.

Let me show you my code to help me please.

I have a class library  LabelData  to make the database and a  data class 
 
this is my table

CREATE TABLE MyTable
(IdTable Int(2),
IdLabel Int(20),
LName char(50)
)

and my  Rows

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (1, 200, 'firstName');

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (2, 200, 'lastName');

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (3, 200, 'middleName');

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (4, 201, 'circuit');

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (5, 201, 'series');

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (6, 202, 'country');

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (7, 202, 'region');

INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (8, 202, 'zipcode');

For make the treeview, I use  IdLabel to make like "categorie"  and i  use LName to make like "product" .

I add a heritance in on my table MyTable   GroupLabel  with the property LName


This is my class  data.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

LNamespace LabelData
{
    public class DataProvider
    {
        LabelDataContext dc;

        public DataProvider()
        {
            dc = new LabelDataContext();
        }

        public IEnumerable<Label> GetLabel()
        {
            return from e in dc.MyTable
                   group e by e.IdLabel into gr
                   select new Label() { IdLabel = gr.Key, LName= gr };

        }

        public IEnumerable<MyTable> Get_Table()
        {
            return from p in dc.MyTable
                   select p;

        }



     }

    public class Label
    {
        public int IdLabel { get; set; }
        public IEnumerable<MyTable> LName{ get; set; }
    }



}

And this is my behind code xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using Telerik.Windows.Controls.GridView;
using Telerik.Windows.Controls.DragDrop;
using Telerik.Windows.Controls;
using System.Collections.ObjectModel;
using LabelData;
using Telerik.Windows.Controls.TreeView;
using System.Collections;

using System.Net;

using System.Windows.Media.Animation;


using Telerik.Windows;


LNamespace LabelMunich
{
    /// <summary>
    /// Logique d'interaction pour MainWindow.xaml
    /// </summary>
    public partial class WindowTreeView : Window
    {
        public WindowTreeView()
        {
            InitializeComponent();
            ProfilData.DataProvider dataProvider = new ProfilData.DataProvider();
            treeView1.ItemsSource = dataProvider.GetModule();
            radGridView.ItemsSource = dataProvider.Get_Table();

            RadDragAndDropManager.AddDropQueryHandler(radGridView, new EventHandler<DragDropQueryEventArgs>(this.RadGridView_OnDropQuery));
            RadDragAndDropManager.AddDropInfoHandler(radGridView, new EventHandler<DragDropEventArgs>(this.RadGridView_OnDropInfo));


        }
        private void RadRibbonButton_Click(object sender, RoutedEventArgs e)
        {
            // FAjout fa = new FAjout();
            formAjout fa = new formAjout();
            fa.Show();
            // this.ShowActivated();
        }

        private void radTreeView_PreviewDragEnded(object sender, RadTreeViewDragEndedEventArgs e)
        {
            e.Handled = true;
        }


        private void RadGridView_OnDropQuery(object sender, DragDropQueryEventArgs e)
        {
            e.QueryResult = (e.Options.Source as RadTreeViewItem).Item is Module;
        }
        private void RadGridView_OnDropInfo(object sender, DragDropEventArgs e)
        {
            if (e.Options.Status == DragStatus.DropComplete)
            {
                (radGridView.ItemsSource as IList<Module>).Add((e.Options.Payload as Collection<Object>)[0] as Module);
            }
        }

    }
}

And my Xaml document

<Window x:Class="ProfilTandem.WindowTreeView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:northwind="clr-namespace:ProfilData;assembly=LabelData"
        xmlns:local="clr-namespace:LabelMunich"
        xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
        xmlns:telerikDragDrop="clr-namespace:Telerik.Windows.Controls.DragDrop;assembly=Telerik.Windows.Controls"
        Title="MainWindow" Height="450" Width="585">
    <Window.Resources>
        <DataTemplate x:Key="Team">
            <TextBlock Text="{Binding  Path=LName}"/>
        </DataTemplate>

        <HierarchicalDataTemplate DataType="{x:Type northwind:Label}" ItemsSource="{Binding Path=LName}">
            <Border Width="250">
                <Grid>
                    <TextBlock
                 Text="{Binding Path=IdLabel}" FontSize="14" FontWeight="Bold" Margin="2" >
                    </TextBlock>
                </Grid>
            </Border>
        </HierarchicalDataTemplate>
        <HierarchicalDataTemplate DataType="{x:Type northwind:GroupLabel}">
            <Grid Margin="6">
                <TextBlock Text="{Binding Path=LName}" Padding="2" />
            </Grid>
        </HierarchicalDataTemplate>
    </Window.Resources>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>

        <telerik:RadTreeView IsDragDropEnabled="True" Grid.Column="0" Grid.Row="1"
               SelectionMode="Multiple"      IsEditable="True"  x:Name="treeView1" Margin="0,20,0,245"
                PreviewDragEnded="radTreeView_PreviewDragEnded"
      IsDragTooltipEnabled="False" ItemsSource="{Binding}"/>

        <StackPanel Grid.Column="1" Grid.Row="1">
            <telerik:RadGridView x:Name="radGridView"  AutoGenerateColumns="False"
          Width="400" Height="400" HorizontalAlignment="Left" telerikDragDrop:RadDragAndDropManager.AllowDrop="True"
          DataContext="{Binding}"   ItemsSource="{Binding}">
                <telerik:RadGridView.Columns>
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding Path=IdLabel}"/>
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding Path=LName}"/>

                    </telerik:RadGridView.Columns>
            </telerik:RadGridView>
        </StackPanel>

    </Grid>
</Window>

This is all


When i try to drag items treeview to gridview i have exception on this line 

  (radGridView.ItemsSource as IList<Label>).Add((e.Options.Payload as Collection<Object>)[0] as Label);

The exception System.NullReferenceException was unhandled

Object reference not set to an instance of an object

Thank you for your help

[Ivan Ivanov]

Hello Goldoni,

Fortunately we have an example that deals with a similar scenario. It can be found here: examples -> Drag and drop -> Tree to Grid. I believe that it will prove useful for your case. Please, do not hesitate to contact us if any further inquires occur.

Kind regards,
Ivan Ivanov
the Telerik team

[Goldoni]

Thank you