Windows.UI.Xaml.Controls.TextBox.GetRectFromCharacterIndex C# (CSharp) Méthode

		public extern Rect GetRectFromCharacterIndex([In] int charIndex, [In] bool trailingEdge);
	}

        // returns a rect for selected text
        // if no text is selected, returns caret location
        // textbox should not be empty
        private Rect GetTextboxSelectionRect(TextBox textbox)
        {
            Rect rectFirst, rectLast;
            if (textbox.SelectionStart == textbox.Text.Length)
            {
                rectFirst = textbox.GetRectFromCharacterIndex(textbox.SelectionStart - 1, true);
            }
            else
            {
                rectFirst = textbox.GetRectFromCharacterIndex(textbox.SelectionStart, false);
            }

            int lastIndex = textbox.SelectionStart + textbox.SelectionLength;
            if (lastIndex == textbox.Text.Length)
            {
                rectLast = textbox.GetRectFromCharacterIndex(lastIndex - 1, true);
            }
            else
            {
                rectLast = textbox.GetRectFromCharacterIndex(lastIndex, false);
            }

            rectFirst.Union(rectLast);

            GeneralTransform transform = textbox.TransformToVisual(null);
            return transform.TransformBounds(rectFirst);
        }