title: checking value changed or not in datetimepicker
body: <p>I have 2 datetimepicker on form having joining and leaving date ,if i dont change these values than it throws exception on total_button_click,since its default value is today's date ,so i want to enable total_button only when datetimepicker value gets changed,can i use any property of datetimepicker for this purpose ,below is the code for total_button</p>
  
  <pre><code>private void Total_button_Click(object sender, EventArgs e)
  {
      int remain, re, d, r;
      string oday;                
      decimal sum = dataGridView1.Rows.OfType&lt;DataGridViewRow&gt;()
              .Sum(row =&gt; Convert.ToDecimal(row.Cells["Money"].Value));
  
      // total amnt drawn
      textBox1.Text = sum.ToString();
      d = int.Parse(textBox3.Text);
      int div = d / 30;
  
      // 1 day payment
      oday = div.ToString();
      textBox6.Text = (dateTimePicker2.Value - dateTimePicker1.Value).TotalDays.ToString("#");
      re = int.Parse(textBox6.Text) * int.Parse(oday);
  
      // total  days paymnt
      textBox7.Text = re.ToString();
      r = int.Parse(textBox7.Text) - int.Parse(textBox1.Text);
  
      // total payment -drawn i.e to b payed                
      textBox8.Text = r.ToString();
  }
  </code></pre>