debug my programme, it’s norml, as the second picture(untitled-1.png),
but, after mouse scroll, it changed like the first picture(untitled-2.png),
the lines seem not to be changed in real-time with the mouse scrolling or sliding the scrollbar,
what’s wrong with my code,how to modify it

///////////////////////////////My Code//////////////////////////////////////////
private void Form1_Load(object sender, EventArgs e)
{
_flex.Cols.Count = 6;
_flex.Rows.Count = 31;
_flex.Cols.DefaultSize = 30;
_flex.Rows.DefaultSize = 30;
_flex.Styles.Normal.TextAlign = TextAlignEnum.CenterCenter;
_flex.Cols[0].Width = 30;
for (int i = 1; i < _flex.Rows.Count; i++)
{
_flex.SetData(i, 0, i);
}
_flex[1, 1] = 0;
_flex[2, 3] = 0;
_flex[3, 2] = 0;
_flex[4, 2] = 0;
_flex[5, 5] = 0;
_flex[6, 1] = 0;
_flex[7, 4] = 0;
_flex[8, 2] = 0;
_flex[9, 3] = 0;
_flex[10, 1] = 0;
_flex[11, 1] = 0;
_flex[12, 3] = 0;
_flex[13, 2] = 0;
_flex[14, 2] = 0;
_flex[15, 5] = 0;
_flex[16, 1] = 0;
_flex[17, 4] = 0;
_flex[18, 2] = 0;
_flex[19, 3] = 0;
_flex[20, 1] = 0;
_flex[21, 1] = 0;
_flex[22, 3] = 0;
_flex[23, 2] = 0;
_flex[24, 2] = 0;
_flex[25, 5] = 0;
_flex[26, 1] = 0;
_flex[27, 4] = 0;
_flex[28, 2] = 0;
_flex[29, 3] = 0;
_flex[30, 1] = 0;
this._flex.Paint += new PaintEventHandler(_flex_Paint);
}

void _flex_Paint(object sender, PaintEventArgs e)
{
//const int DefaultColWidth = 30;
//const int DefaultRowHeight = 30;
int x1 = 0;
int y1 = 0;
int x2 = 0;
int y2 = 0;

System.Drawing.Pen myPen = new System.Drawing.Pen(System.Drawing.Color.Red);
System.Drawing.Graphics formGraphics = e.Graphics;

for (int i = 1; i < _flex.Rows.Count – 1; i++)
{
for (int j = 1; j < _flex.Cols.Count; j++)
{
var v = _flex;
if (v != null && v.ToString() == "0″)
{
x1 = _flex.Cols[j].Left + DefaultColWidth / 2;
break;
}
}