using System . Runtime . InteropServices;
[ DllImport ( "User32.DLL" )]
public static extern int SendMessage( IntPtr hWnd, uint Msg, int wParam, int iParam);
private const int EM_LINEFROMCHAR = 0xC9 ;
private const int EM_LINEINDEX = 0xBB ;
private void button6_Click( object sender, EventArgs e)
{
int Y = SendMessage(textBox1 . Handle, EM_LINEFROMCHAR, textBox1 . SelectionStart, 0 );
int X = SendMessage(textBox1 . Handle, EM_LINEINDEX, Y, 0 ); //
}
// or
int Y = textBox1 . GetLineFromCharIndex(textBox1 . SelectionStart);
int X = textBox1 . GetFirstCharIndexFromLine(Y);