By default the TextSearchPath of RadAutoCompleteBox is automatically assigned when the DisplayMemberPath is set, and if the TextSearchPath is not yet assigned. However, this happens only initially. Runtime changes of the DisplayMemberPath don't update the text search path.

To work this around, set the TextSearchPath manually when you change the DisplayMemberPath.

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

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

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();
            }
        }