GridView throws Null Reference error when GridViewComboBox column is bound to a list of objects and the list changes

[Randy]

When GridView has a GridViewComboBoxColumn that is bound to a list of objects and that list changes a null reference error is thrown.  This error did not get throw in the previous release (2013 Q1), it just started happening in (2013 Q2, specifically 2013.2.612.40).

Here is a code example using a list of Authors and a list of books.  Basically the book object has a reference to the Author object.  When the author list changes the book grid will throw a null reference error.

Here is the stack trace of the error:

   at Telerik.WinControls.UI.GridViewComboBoxColumn.AddItem(Int32 i)
   at Telerik.WinControls.UI.GridViewComboBoxColumn.currencyManager_ListChanged(Object sender, ListChangedEventArgs e)
   at System.ComponentModel.ListChangedEventHandler.Invoke(Object sender, ListChangedEventArgs e)
   at System.Windows.Forms.CurrencyManager.OnListChanged(ListChangedEventArgs e)
   at System.Windows.Forms.CurrencyManager.List_ListChanged(Object sender, ListChangedEventArgs e)
   at System.ComponentModel.BindingList`1.OnListChanged(ListChangedEventArgs e)
   at System.ComponentModel.BindingList`1.Child_PropertyChanged(Object sender, PropertyChangedEventArgs e)
   at GridTest.Author.NotifyPropertyChanged(String info) in c:\Users\SESA124669\Documents\Visual Studio 2012\Projects\GridTest\GridTest\Form1.cs:line 69
   at GridTest.Author.set_Name(String value) in c:\Users\SESA124669\Documents\Visual Studio 2012\Projects\GridTest\GridTest\Form1.cs:line 97
   at GridTest.Form1.button1_Click(Object sender, EventArgs e) in c:\Users\SESA124669\Documents\Visual Studio 2012\Projects\GridTest\GridTest\Form1.cs:line 52
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at GridTest.Program.Main() in c:\Users\SESA124669\Documents\Visual Studio 2012\Projects\GridTest\GridTest\Program.cs:line 19
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

Here is the code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Telerik.WinControls.UI;

namespace GridTest
{
    public partial class Form1 : Form
    {
        private BindingList<Author> AuthorData = new BindingList<Author>();
        private BindingList<Book> BookData = new BindingList<Book>();

        public Form1()
        {
            InitializeComponent();

            radGridViewAuthors.DataSource = AuthorData;

            radGridViewBooks.MasterTemplate.Columns.Clear();

            GridViewComboBoxColumn colAuth = new GridViewComboBoxColumn("Author");
            colAuth.HeaderText = "Author";
            colAuth.Name = "Author";
            colAuth.DataSource = AuthorData;
            colAuth.ValueMember = "Id";
            colAuth.DisplayMember = "Name";
            colAuth.DisplayMemberSort = true;
            radGridViewBooks.MasterTemplate.Columns.Add(colAuth);

            GridViewTextBoxColumn colName = new GridViewTextBoxColumn("Name");
            colName.HeaderText = "Name";
            colName.Name = "Name";
            colName.ReadOnly = true;
            radGridViewBooks.MasterTemplate.Columns.Add(colName);

            radGridViewBooks.MasterTemplate.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;

            radGridViewBooks.DataSource = BookData;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Author m = new Author();
            m.Id = AuthorData.Count + 1;
            AuthorData.Add(m);
            m.Name = textBoxAuthorName.Text;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Book m = new Book(textBoxBookName.Text);
            BookData.Add(m);
        }
    }

    public class Author : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }

        private int id;
        public int Id
        {
            get
            {
                return id;
            }
            set
            {
                id = value;
                NotifyPropertyChanged("Id");
            }
        }

        private string name;
        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
                NotifyPropertyChanged("Name");
            }
        }

        public Author() { }
        public Author(int id, string name)
        {
            Id = id;
            Name = name;
        }
    }

    public class Book : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }

        private string name;
        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
                NotifyPropertyChanged("Name");
            }
        }

        private Author author;
        public Author Author
        {
            get
            {
                return author;
            }
            set
            {
                author = value;
                NotifyPropertyChanged("Author");
            }
        }

        public Book() { }
        public Book(string name)
        {
            Name = name;
        }
    }
}

[George]

Hello Randy,

Thank you for contacting us.

I have reviewed your case carefully. The exception is caused by the fact that the combobox can not initialize itself properly when the binding list is empty. I have added a feature request for that in our Public Issue Tracking System you can subscribe to track it for changes and vote for it on this address http://www.telerik.com/support/pits.aspx#/public/winforms/15413. For the time being a possible workaround is to add a dummy object to the binding list before binding it to the grid and the column and remove it after that. If the scenario with binding list is hard to maintain I would recommend you to use a DataTable. I am also uploading my test project just in case you need it. Additionally I have updated your Telerik Points as a token of gratitude for the request.

Hope this helps, if you have any other questions or comments, please let me know.
 
Regards,
George
Telerik