A long expression that indicates the index of line being selected. The index is
1 based.
Use the SelectLine method to select a line by code. Use the
SelText property to retrieve the selected text.
Use the GetSelection method to determine
the coordinates of the selected text. Use the SetSelection
method to select a text giving the end and start coordinates. The SelStart
property returns or sets the starting point of text selected; indicates the
position of the insertion point if no text is selected.
