When the SelectionMode of RadAutoCompleteBox is changed, the search text is cleared. However, this clears only the Text property of the underlying TextBox element. The SearchText property of the control is not cleared.

this.autoCompleteBox.SelectionMode = AutoCompleteSelectionMode.Multiple;
this.autoCompleteBox.SearchText = null;

The documentation for WPF FilteringBehavior.FindMatchingItems, <http://docs.telerik.com/devtools/wpf/api/html/M_Telerik_Windows_Controls_FilteringBehavior_FindMatchingItems.htm>, only tells the type of the parameters.  It does not tell what the parameters do, nor does it tell what the function does.

Available in LIB version 2016.3.1017, it will be also available in the 2016 R3 SP1 release. 

The current workaround is to directly set the value of the underlying TextBox instead:

this.RadAutoCompleteBox.ChildrenOfType<TextBox>().First().Text = "1 I";

The workaround is to set String.Empty for TextSearchPath before setting the new value for the DisplayMemberPath

Available in the R3 2016 Release.

Please check our help article for more information:
http://docs.telerik.com/devtools/wpf/controls/radautocompletebox/features/key-properties#setting-noresultscontent-noresultscontenttemplate-properties

After removing an item with it's remove "X" button, two mouse clicks are required in order to lose the focus from the control.

Available in LIB version 2016.2.606, it will be also available in the 2016 R2 SP1 release.

Clicking the ScrollViewer of the control causes the focus to be retained by the RadAutoCompleteBox, leading to double mouse click required in order to access outside control.

Also the mouse cursor is changed IBeam value rather than the default Arrow value.

The fix is available in the 2016 R3 SP1 release.

Should be clicked somewhere else afterwards in order to refresh the cursor.
The fix is available in R2 2016 SP1.

When you start typing, the dropdown appears and then you leave the AutoCompleteBox without clicking, the cursor is not changing back to arrow.

As a workaround of the issue you could manually release the mouse capture in the Populated event handler of the control as shown below:


 private void AutoCompleteBox_Populated(object sender, System.EventArgs e)
        {
            if (Mouse.Captured is RadAutoCompleteBox)
            {
                (sender as RadAutoCompleteBox).ReleaseMouseCapture();
            }
        }

In Multiple SelectionMode it would be useful to be able to customize the way selected items (boxes) are displayed. Customizing their looks via a StyleSelector would be optimal.