private void ButtonSave_Click(object sender, EventArgs e)
 {
     if (ID == null)
     {
         if (validation.check("date", dateTimePicker1.Value, dateTimePicker2.Value))
         {
             ID = serviceCC.AddElement(new ModelContractClient
             {
                 AgentId   = Convert.ToInt32(comboBoxAgent.SelectedValue),
                 ClientId  = Convert.ToInt32(comboBoxClient.SelectedValue),
                 DateStart = dateTimePicker1.Value,
                 DateEnd   = dateTimePicker2.Value,
                 Sum       = Convert.ToDouble(textBoxSum.Text)
             });
             LoadData();
         }
     }
     else
     {
         if (validation.check("date", dateTimePicker1.Value, dateTimePicker2.Value))
         {
             serviceCC.UpdElement(new ModelContractClient
             {
                 Id        = Convert.ToInt32(ID),
                 AgentId   = Convert.ToInt32(comboBoxAgent.SelectedValue),
                 ClientId  = Convert.ToInt32(comboBoxClient.SelectedValue),
                 DateStart = dateTimePicker1.Value,
                 DateEnd   = dateTimePicker2.Value,
                 Sum       = Convert.ToDouble(textBoxSum.Text)
             });
             LoadData();
         }
     }
 }