Question

want to create a selectionRangeChanged event programatically not really getting how to do it

 private void btn_10D_Click(object sender, EventArgs e)
    {
        double varRange = 10;
        double var_Sel1 = DatesX[0].ToOADate();

        Chart1.ChartAreas["ChartArea1"].CursorX.IsUserEnabled = true;
        Chart1.ChartAreas["ChartArea1"].CursorX.IsUserSelectionEnabled = true;
        Chart1.ChartAreas["ChartArea1"].CursorX.SelectionColor = Color.LightGray;
        Chart1.ChartAreas["ChartArea1"].CursorX.SelectionStart = var_Sel1;
        Chart1.ChartAreas["ChartArea1"].CursorX.SelectionEnd = varRange + var_Sel1;
        Chart1.ChartAreas["ChartArea1"].CursorX.Position = varRange + var_Sel1;
        Chart1.SelectionRangeChanged += new EventHandler<CursorEventArgs>(Chart1_SelectionRangeChanged);

    }

    void Chart1_SelectionRangeChanged(object sender, CursorEventArgs e)
    {
        throw new NotImplementedException();
    }

thank you

Answer 1

For all events in C# is true that if class creator did not make extra effort to allow event firing form outside of class it is impossible to fire them.

According to MSDN

Chart.SelectionRangeChanged event Occurs when the selection start position or end position is changed.

But from my tests I can see that it is fired only if it is changed by user not program.

If I understand your intention correctly you want to handle those small buttons under your chart and btn_10D_Click method is a click handler for one of them. Try to move this line

Chart1.SelectionRangeChanged += new EventHandler<CursorEventArgs>(Chart1_SelectionRangeChanged);

to your constructor and ensure it is called once (remove it form other handlers). This will ensure your code is executed when user changes selection. If you want to execute same code for your button you should simply extract handler contents to method and call it form button click handler.

void Chart1_SelectionRangeChanged(object sender, CursorEventArgs e)
{
    DoSomething(/*some arguments if you need them*/);
}
private void btn_10D_Click(object sender, EventArgs e)
{
     \\your code
     DoSomething();
 }