Despite the fact that the elements of RadTextBox have ToolTipText and AutoToolTip properties, one can't set the tooltip at design-time. We should consider whether we should continue using these properties or introduce a new method to allow for setting tooltips at design-time.

Resolution:
Open 'Edit UI elements' and set the Tooltip property of RadTextBoxItem 

You can't set the focus to the hosted textbox control in RadTextBox by calling Select or Focus on the control.

You can't cancel the TextChanging event of RadTextBoxElement by setting e.Cancel to true.

Handling of KeyPress event of RadTextBoxControl does not suppress inserting new character.

The spellchecker gives wrong suggestion for the word didn't't in both spelling modes.

The last caret position in RadTextBoxControl is not aligned to the end of the text due to wrong text measurement.

On Win XP machine add RadTextBoxControl (Multiline=true) and start typing a very long text with no blank space between letters. As a result the caret is taken away from the last letter and if you use left arrow to return it back, the caret is positioned in the middle of the letter.

Inserting @ symbol fails when french culture is used in RadTextBoxControl

Double click on item from auto-complete drop down appends the item twice in RadAutoCompleteBox.

The RadDateTimeEditor does not obey MaxDate and MinDate property when the value is changed by keyboard input.

Work around:

public class MyRadDateTimeEditor : RadDateTimeEditor
    {
        public MyRadDateTimeEditor()
        {
            RadDateTimeEditorElement element = this.EditorElement as RadDateTimeEditorElement;
            element.CurrentBehavior.TextBoxElement.ValueChanged += this.OnValueChanged;
        }

        private void OnValueChanged(object sender, System.EventArgs e)
        {
            RadMaskedEditBoxElement maskBox = sender as RadMaskedEditBoxElement;
            RadDateTimeEditorElement element = this.EditorElement as RadDateTimeEditorElement;

            DateTime result;

            if (maskBox.Value != null && DateTime.TryParse(maskBox.Value.ToString(), out result) && DateTime.Compare(result, element.MaxDate) > 0)
            {
                this.Value = element.MaxDate;
                maskBox.Value = element.MaxDate;
                return;
            }
        }
    }

The RadAutoCompleteBox does not show its dropdown when single item is suggested.

Fix suggest behavior in RadAutoCompleteBox to support spaces in the written text.

WORKAROUND:
public class MyAutoCompleteBox : RadAutoCompleteBox
    {
        public MyAutoCompleteBox()
        {
            this.ThemeClassName = typeof(RadAutoCompleteBox).FullName;
        }

        protected override RadTextBoxControlElement CreateTextBoxElement()
        {
            return new MyAutoCompleteBoxElement();
        }
    }

 public class MyAutoCompleteBoxElement : RadAutoCompleteBoxElement
    {
        protected override Type ThemeEffectiveType
        {
            get { return typeof(RadAutoCompleteBoxElement); }
        }

        public override void CloseDropDown(RadPopupCloseReason reason)
        {
            if (reason == RadPopupCloseReason.CloseCalled)
            {
                if (this.ListElement.SuggestedText != null && this.ListElement.PatternText != null && this.ListElement.IsSuggestionMatched)
                {
                    return;
                }
            }

            base.CloseDropDown(reason);
        }

        protected override RadTextBoxListElement CreateListElement()
        {
            return new RadTextBoxListElement();
        }
    }

If the null date of RadDateTimePicker is current date, you cannot set its value to the same date.

When MaskType is Numeric and Mask is currency ("C") selecting the last two digits and trying to enter value for them results in moving the caret at the end of the last digit right after entering the first number.

When RadDateTimePicker value is set to null then you are not able to enter in the control, a date which is less than the NullValue date.

RadMaskEditBox - When MaskType is Numeric and Mask is currency ("C") pasting a value (9.99) results in 09.99.00

Steps to reproduce:

1. Add a RadPropertyGrid to a form.
2. Select an object with DateTime property
3. Subscribe to the EditorInitialize event and set min and max date.
4. Run the application and open the property for edit. Type in a value outside the valid range and end edit. You will see that the invalid value is saved.

When the Office2007Black theme is used, the items in the dialog's page view are not visible. 

Workaround: set the form's BackColor:
((RadColorDialogForm)radColorDialog1.ColorDialogForm).BackColor = Color.FromArgb(103, 103, 103);

RadMaskedEditBox - has incorrect behavior if you set values with differed length.

Workaround is to reset the value before to set new one:

C#
RadMaskedEditBox1.Value = null;
RadMaskedEditBox1.Value = "YourText";

VB
RadMaskedEditBox1.Value = Nothing
RadMaskedEditBox1.Value = "YourText"

RadMaskEditBox - Wrong cursor placement after typing decimal separator (it goes to the last position) when you change Decimal symbols for Currency as ";"

Workaround:
            this.radMaskedEditBox2.KeyPress += new KeyPressEventHandler(radMaskedEditBox2_KeyPress);
            this.radMaskedEditBox2.KeyUp += new KeyEventHandler(radMaskedEditBox2_KeyUp);
        }

        void radMaskedEditBox2_KeyPress(object sender, KeyPressEventArgs e)
        {
            string separtor = Thread.CurrentThread.CurrentCulture.NumberFormat.CurrencyDecimalSeparator;

            if (e.KeyChar.ToString() == separtor)
            {
                e.Handled = true;
            }
        }

        void radMaskedEditBox2_KeyUp(object sender, KeyEventArgs e)
        {
            if (e.KeyValue == 186)
            {
                RadMaskedEditBoxElement radMaskedEditBoxElement = sender as RadMaskedEditBoxElement;
                int index = radMaskedEditBoxElement.TextBoxItem.Text.IndexOf(';');
                radMaskedEditBoxElement.TextBoxItem.SelectionStart = index + 1;
            }
        }

To reproduce:

Add the following line of code: 
[C#]
this.radSpellChecker1.SpellCheckMode = Telerik.WinControls.UI.SpellCheckMode.AllAtOnce;
[VB.NET]
Me.RadSpellChecker1.SpellCheckMode = Telerik.WinControls.UI.SpellCheckMode.AllAtOnce

When you spell check RadRichTextBox and the spell check form is opened click the change button. You will notice that the word will not changed in the original RadRichTextBox.

this.radSpellChecker1.RegisterControlSpellChecker(typeof(RadRichTextBox), new MyRichTextBoxSpellChecker());
this.radSpellChecker1.SpellCheckMode = SpellCheckMode.AllAtOnce;

Workaround:
class MyRichTextBoxSpellChecker : RadRichTextBoxSpellChecker
{
    public override Telerik.WinControls.RichTextBox.Model.RadDocument GetContentAsDocument()
    {
        return (this.CurrentControl as RadRichTextBox).Document;
    }
}