To reproduce: please refer to the attached gif file.

The error is not reproduced each time with the Demo application. Sometimes an unhandled exception dialog appears and sometimes the application becomes unresponsive and you can not close the application with upper right X, the options to the right does not respond, you can not change demo using the list on the left. Selecting "Settings" in Property Grid section and then clicking on a boolean property (left column), scrolling using the mouse wheel, then selecting another property (with PropertyGridDropDownListEditor) or clicking around in the application (even outside of the property grid form).

Workaround:   this.radPropertyGrid1.EditorRequired += radPropertyGrid1_EditorRequired;

private void radPropertyGrid1_EditorRequired(object sender, PropertyGridEditorRequiredEventArgs e)
{
    if (e.EditorType == typeof(PropertyGridDropDownListEditor))
    {
        e.Editor = new CustomPropertyGridDropDownListEditor();
    }
}

public class CustomPropertyGridDropDownListEditor : PropertyGridDropDownListEditor
{
    public override object Value
    {
        get
        {
            PropertyGridItemElement element = this.OwnerElement as PropertyGridItemElement;
            PropertyGridItem item = element.Data as PropertyGridItem;
            if (item == null)
            {
                return null;
            }
            return base.Value;
        }
        set
        {
            base.Value = value;
        }
    }
}

The RadPropertyGrid columns should be able to auto resize according to their cells content.

To reproduce: use the following code snippet and refer to the attached gif file:

 public Form1()
 {
     InitializeComponent(); 
     this.radPropertyGrid1.SelectedObject = this;
 }

 private void radButton1_Click(object sender, EventArgs e)
 {
     ThemeResolutionService.ApplicationThemeName = "VisualStudio2012Dark";
 }

 private void radButton2_Click(object sender, EventArgs e)
 {
     ThemeResolutionService.ApplicationThemeName = "ControlDefault";
 }


Workaround:

private void radPropertyGrid1_EditorInitialized(object sender, PropertyGridItemEditorInitializedEventArgs e)
{
    PropertyGridTextBoxEditor editor = e.Editor as PropertyGridTextBoxEditor;
    if (editor != null)
    {
        BaseTextBoxEditorElement el = editor.EditorElement as BaseTextBoxEditorElement;
        if (el != null)
        {
            el.BackColor = Color.Black;
        }
    }
}

Workaround:
 Private Sub RadPropertyGrid1_EditorRequired(sender As Object, e As PropertyGridEditorRequiredEventArgs) Handles RadPropertyGrid1.EditorRequired
     Dim te As PropertyGridTableElement = TryCast(sender, PropertyGridTableElement)
     If e.EditorType = GetType(PropertyGridSpinEditor) Then
         Dim editor As New CustomPropertyGridSpinEditor
         If editor IsNot Nothing AndAlso te IsNot Nothing Then
             Dim type As Type = RadPropertyGrid1.SelectedObject.[GetType]().GetProperty(e.Item.Name).PropertyType
             If type = GetType(System.Double) Then
                 DirectCast(editor.EditorElement, BaseSpinEditorElement).DecimalPlaces = 4
                 e.Editor = editor
             End If
         End If
     End If
 End Sub

 Public Class CustomPropertyGridSpinEditor
     Inherits PropertyGridSpinEditor
     Public Overrides Sub Initialize(owner As Object, value As Object)
         Dim decimalPlaces As Integer = Me.DecimalPlaces
         MyBase.Initialize(owner, value)

         Dim element As PropertyGridItemElement = TryCast(owner, PropertyGridItemElement)
         Dim item As PropertyGridItem = TryCast(element.Data, PropertyGridItem)
         Dim editedType As Type = item.PropertyType

        If ((editedType = GetType(Decimal) OrElse editedType = GetType(Double) OrElse editedType = GetType(Single)) AndAlso decimalPlaces <> 0) Then
         DirectCast(Me.EditorElement, BaseSpinEditorElement).DecimalPlaces = decimalPlaces
         Me.Value = value
       End If
     End Sub
 End Class

To reproduce: run the attached sample project and follow the steps from the gif file.

Workaround: cancel the edit operation when handling the MouseDown event of RadPropertyGrid:

        private void radPropertyGrid1_MouseDown(object sender, MouseEventArgs e)
        {
            var elementUnderMouse = this.radPropertyGrid1.ElementTree.GetElementAtPoint(e.Location).FindAncestor<RadScrollBarElement>();
            if (elementUnderMouse!=null)
            {
                this.radPropertyGrid1.CancelEdit();
            } 
        }

Add the ability for custom sorting in the RadPropertyGrid.

To reproduce: use the following code snippet and follow the steps from the gif file:

            PropertyStoreItem item1 = new PropertyStoreItem(typeof(string), "Test1", "Test1");
            PropertyStoreItem item2 = new PropertyStoreItem(typeof(string), "Test2", "Test2");
          
            RadPropertyStore store = new RadPropertyStore();
            store.Add(item1);
            store.Add(item2); 
            this.radPropertyGrid1.SelectedObject = store;

            this.radPropertyGrid1.ToolbarVisible = true;

Workaround: close the editor programmatically when the search box gets focus.

this.radPropertyGrid1.PropertyGridElement.ToolbarElement.SearchTextBoxElement.TextBoxItem.GotFocus += TextBoxItem_GotFocus;

        private void TextBoxItem_GotFocus(object sender, EventArgs e)
        {
            this.radPropertyGrid1.EndEdit();
        }

Please run the attached sample project and refer to the attached screenshots. RadPropertyGrid doesn't respect the Description attribute.

 this.radPropertyGrid1.SelectedObject = new Item(123,"Item", ExposureMode.FullAuto);

public class Item
{
    public int Id { get; set; }

    public string Name { get; set; }

    public ExposureMode Mode { get; set; }

    public Item(int id, string name, ExposureMode mode)
    {
        this.Id = id;
        this.Name = name;
        this.Mode = mode;
    }
}

public enum ExposureMode
{
    [Description("Full Auto")]
    FullAuto,
    [Description("Auto Filter, Fixed Exposure")]
    AutoFilFixedExp,
    [Description("Fixed Filter, Auto Exposure")]
    FixedFilAutoExp,
    [Description("Fixed Filter, Fixed Exposure")]
    FullFixed
}

Workaround use the attached custom theme: http://docs.telerik.com/devtools/winforms/themes/using-custom-themes

Generic collections are used by entity framework to contain child objects.

UPDATE: RadPropertygrid uses the standard System.ComponentMode.Design.CollectionEditor when editing collections. The editor requirements are that the collection being edited implements the IList interface and that it has an indexer (Item in VB.NET) property. Entity Framework generates an ICollection<T> property which holds a HasSet<T> object. This does not fit both requirements of the editor and prevents it from working correctly.

Steps to reproduce:
1. Add a RadPropertyGrid to a form
2. Set the SelectedObject property to an object with an enum property
3. Open the enum property for edit.
4. Click on another control that can take focus e.g. the form control box buttons
You will see that the editor remains open.

How to create a PropertyGrid and initialize it like this,modify the 'segments' arraies as I modify the 'count'

Please run the sample project on a monitor with 150 DPI scaling. You will notice that the first time the drop down is not scaled properly and it is clipped. However, each next opening of the drop down, the popup is scaled correctly:

When you have  a property that is bool? or ToggleState, it would be good to have three-state functionality for the PropertyGridCheckBoxItemElement.

Developers should be able to validate user input in the RadPropertyStore items.

UPDATE: Currently we have decided to stick with the current implementation where all the validation is done through the PropertyValidating/ed events.

Currently editors not shown as dialog do not work as the RadPropertyGrid editor is closed when focus is transferred to the dialog form.

To reproduce:

Public Class RadForm1
    Sub New()        
        InitializeComponent()
        RadPropertyGrid1.SelectedObject = New MyProperties
    End Sub

    Public Class MyProperties

        Private _height As Integer = 70
        <Browsable(True)> <Category("Rows")> <DisplayName("Height")> _
        <Description("Sets the height of the row. Range 70 to 200.")> _
        <RadRange(70, 200)> _
        Public Property Height() As Integer
            Get
                Return _height
            End Get
            Set(ByVal Value As Integer)
                _height = Value
            End Set
        End Property
    End Class
End Class

When you activate the editor you will notice that you are allowed to enter values outside the specified range 7-200.

Workaround:

AddHandler Me.RadPropertyGrid1.EditorInitialized, AddressOf PropertyGridEditorInitialized

    Private Sub PropertyGridEditorInitialized(sender As Object, e As PropertyGridItemEditorInitializedEventArgs)
        Dim spinEditor As PropertyGridSpinEditor = TryCast(e.Editor, PropertyGridSpinEditor)
        If spinEditor IsNot Nothing Then
            spinEditor.MinValue = 70
            spinEditor.MaxValue = 200
        End If

    End Sub

Add a RadPropertyGrid and change its Dock property to Fill. Use the following code:

public partial class Form1 : Form
{
    RadPropertyStore _store;

    public Form1()
    {
        InitializeComponent();
        this.radPropertyGrid1.CreateItemElement += new CreatePropertyGridItemElementEventHandler(this.onCreateItemElement);
        _store = new RadPropertyStore();

        PropertyStoreItem barItem = new PropertyStoreItem(typeof(Int32), "TrackBar", 25);
        _store.Add(barItem);

        PropertyStoreItem sec = new PropertyStoreItem(typeof(bool), "Checkr", true);
        _store.Add(sec);

        this.radPropertyGrid1.SelectedObject = _store;
    }

    private void onCreateItemElement(object sender, CreatePropertyGridItemElementEventArgs e)
    {
        PropertyGridItem item = e.Item as PropertyGridItem;

        if (item != null)
        {
            if (item.Name == "TrackBar")
            {
                e.ItemElementType = typeof(TrackBarPropertyGridItem);
            }
        }
    }
}

public class TrackBarPropertyGridItem : PropertyGridItemElement
{
    protected override PropertyGridValueElement CreatePropertyGridValueElement()
    {
        return new CustomPropertyGridValueElement(); 
    }
}

public class CustomPropertyGridValueElement : PropertyGridValueElement
{
    RadTrackBarElement _trackbar;

    public RadTrackBarElement Trackbar
    {
        get
        {
            return this._trackbar;
        }
    }

    protected override void CreateChildElements()
    {
        base.CreateChildElements();

        _trackbar = new RadTrackBarElement();
        _trackbar.Minimum = 0;
        _trackbar.Maximum = 100;
       
        this.DrawText = false;
        this.Children.Add(_trackbar);
    }
}



When resizing the form, the applications hangs.

Workaround:

/// <summary>
    /// Track bar property grid element
    /// </summary>
    public class TrackBarPropertyGridItem : PropertyGridItemElement
    {
        class MyTrackBarElement : RadTrackBarElement
        {
            protected override void OnNotifyPropertyChanged(string propertyName)
            {
                if (propertyName == "TickOffSet" || propertyName == "ThumbSize")
                {
                    this.BodyElement.ScaleContainerElement.InvalidateMeasure();
                    this.BodyElement.IndicatorContainerElement.InvalidateMeasure();
                    return;
                }

                base.OnNotifyPropertyChanged(propertyName);
            }

            protected override Type ThemeEffectiveType
            {
                get
                {
                    return typeof(RadTrackBarElement);
                }
            }
        }

        /// <summary>
        /// The trackbar element to be displayed in the cell
        /// </summary>
        private RadTrackBarElement _trackbar;

        /// <summary>
        /// Accessor to the track bar element
        /// </summary>
        public RadTrackBarElement Trackbar
        {
            get { return _trackbar; }
        }

        /// <summary>
        /// Create child elements of the propertyGridItem
        /// </summary>
        protected override void CreateChildElements()
        {
            base.CreateChildElements();

            _trackbar = new MyTrackBarElement();
            _trackbar.Minimum = 0;
            _trackbar.Maximum = 100;
            _trackbar.ShowTicks = false;


            this.ValueElement.DrawText = false;
            this.ValueElement.Children.Add(this._trackbar);
        }

        /// <summary>
        /// Synchronise the value with property grid item
        /// </summary>
        public override void Synchronize()
        {
            base.Synchronize();

            PropertyGridItem item = this.Data as PropertyGridItem;

            this._trackbar.Value = (int)item.Value;
        }


        /// <summary>
        /// Add editor override
        /// </summary>
        /// <param name="editor">input editor</param>
        public override void AddEditor(IInputEditor editor)
        { }

        /// <summary>
        /// Remove editor override
        /// </summary>
        /// <param name="editor">input editor</param>
        public override void RemoveEditor(IInputEditor editor)
        { }

        /// <summary>
        /// Check if the item is comptable with trackbar editor
        /// </summary>
        /// <param name="data">item to check</param>
        /// <param name="context">context</param>
        /// <returns>true if compatible, false otherwise</returns>
        public override bool IsCompatible(PropertyGridItemBase data, object context)
        {
            PropertyGridItem item = data as PropertyGridItem;
            return (item != null && item.PropertyType == typeof(int));
        }

        /// <summary>
        /// Get the type of the property grid element
        /// </summary>
        protected override Type ThemeEffectiveType
        {
            get { return typeof(PropertyGridItemElement); }
        }

To reproduce:

Follow this article http://www.telerik.com/help/winforms/propertygrid-features-custom-grouping.html . You will notice that the CustomGrouping event will not fire.