c# - textbox 마우스휠로 값 증가, 감소

static Int32 Atoi(string s)//20200611
{
    return Convert_ToInt32(s);
}
void TextBox_Value_inc(TextBox tb,int v)
{
    tb.Text = (Atoi(tb.Text) + v).ToString();
}
void Textbox_MouseWheel(object sender, MouseEventArgs e)
{
    int v;
    if (e.Delta >0)
    {
        v = 1;
    }
    else//if (e.Delta <0)
    {
        v = -1;
    }
    TextBox_Value_inc((TextBox)sender, v);
}
private void Form1_Load(object sender, EventArgs e)
{
	...
	Textbox_1.MouseWheel +=Textbox_MouseWheel;
}