Need to update the chart values in C# windows app without using chart1.refresh

I am using in C# windows Application

My Code
Button 1: To Plot the Values in Graph
Button 2: Update The Particular Axis Value with the old Maximum Value in the axis + new value
My Values are increasing properly,,,
eg i have (x=1,y=2) updating y=2,so old max val=2+2=>4 so My result is (1,4),its working ,but when i give y=-10 the graph is plotting to but the old (1,4) marked size is still visibled
My Code


private void button1_Click(object sender, EventArgs e)
{
chart1.Series.Clear();
chart1.Series.Add(name);
chart1.ChartAreas[0].AxisY.Maximum = double.NaN;
chart1.ChartAreas[0].AxisY.Minimum = double.NaN;
chart1.ChartAreas[0].AxisX.Maximum = double.NaN;
chart1.ChartAreas[0].AxisX.Maximum = double.NaN;
chart1.Series[name].Points.AddXY(1, 2);
chart1.Series[name].Points.AddXY(2, 10);
chart1.Series[name].Points.AddXY(3, 5);
chart1.Series[name].Points.AddXY(4, 8);
chart1.Series[name].Points.AddXY(5, 10);
chart1.Update();
}

private void button2_Click(object sender, EventArgs e)
{
X = double.Parse(textBox1.Text);//added today
if (MyTempXValue != X)
{
try
{
MaximumValue = 0;
chart1.Update();
X = double.Parse(textBox1.Text);
double point = X - 1;
MaximumValue = chart1.Series[name].Points[(int)point].GetValueByName("Y");
MessageBox.Show(MaximumValue.ToString());
double UerValue = double.Parse(textBox3.Text);
Y = MaximumValue + UerValue;
MyTempValue = Y;//storing Maximum Value in temp variable
MyTempXValue = X;//storing the X value in Temp Variable /added today
chart1.Series[name].Points.AddXY(X, Y);
chart1.DataBind();
chart1.Update();
chart1.Invalidate();
}
catch (Exception ex) { MessageBox.Show(ex.Message.ToString()); }
}
else
{
try
{
MessageBox.Show(MyTempValue.ToString());
chart1.Update();
X = double.Parse(textBox1.Text);
double point = X - 1;
double UerValue = double.Parse(textBox3.Text);
MyTempValue = MyTempValue + UerValue;
chart1.Series[name].Points.AddXY(X, MyTempValue);
chart1.DataBind();
chart1.Update();
}
catch (Exception ex) { MessageBox.Show(ex.Message.ToString()); }
}
}