title: Input string was not in a correct format
body: <p>I'm trying to make a simple application form were user can input data like <code>'reservationid', 'bookid', 'EmployeeID' and 'reservedate'</code>. Its from my program Library System. <code>'reservationid' is an auto increment primary key</code> while the rest are <code>BigInt50, NVarChar50 and DateTime10</code> respectively. So I'm having this error: <code>Input String was not in a correct format</code>. <code>It worked fine a while ago until I modified the 'reservationid' to auto increment</code> so where did I go wrong? I've attached a sample of my code behind. </p>
  
  <p>Any help would be greatly appreciated! Thanks in advance!</p>
  
  <pre><code>namespace LibraryManagementSystemC4.User
  {
      public partial class Reserving : System.Web.UI.Page
      {
          public string GetConnectionString()
          {
              return System.Configuration.ConfigurationManager.ConnectionStrings["LibrarySystemConnectionString"].ConnectionString;
          }
          //string reservationid
          private void ExecuteInsert(string bookid, string EmployeeID, string reservedate)
          {
              SqlConnection conn = new SqlConnection(GetConnectionString());
  
              string sql = "INSERT INTO BookReservation (reservationid, bookid, EmployeeID, reservedate) VALUES " + " (@reservationid, @bookid, @EmployeeID, @reservedate)";
              try
              {
                  conn.Open();
                  SqlCommand cmd = new SqlCommand(sql, conn);
                  SqlParameter[] param = new SqlParameter[3];
  
                  //param[0] = new SqlParameter("@reeservationid", SqlDbType.Int, 50);
                  param[0] = new SqlParameter("@bookid", SqlDbType.BigInt, 50);
                  param[1] = new SqlParameter("@EmployeeID", SqlDbType.NVarChar, 50);
                  param[2] = new SqlParameter("@reservedate", SqlDbType.DateTime, 10);
  
                  //param[0].Value = reservationid;
                  param[0].Value = bookid;
                  param[1].Value = EmployeeID;
                  param[2].Value = reservedate;
  
                  for (int i = 0; i &lt; param.Length; i++)
                  {
                      cmd.Parameters.Add(param[i]);
                  }
  
                  cmd.CommandType = CommandType.Text;
                  cmd.ExecuteNonQuery();
              }
  
              catch (System.Data.SqlClient.SqlException ex)
              {
                  string msg = "Insert error";
                  msg += ex.Message;
                  throw new Exception(msg);
              }
  
              finally
              {
                  conn.Close();
              }
          }
  
          protected void Page_Load(object sender, EventArgs e)
          {
              if (reservationidTextBox != null)
              {
                  //reservationidTextBox.Text
                  ExecuteInsert(bookidTextBox.Text, EmployeeIDTextBox.Text, reservationidTextBox.Text);
  
                  ClearControls(Page);
              }
  
              else
              {
                  Response.Write("Please input ISBN");
                  bookidTextBox.Focus();
              }
  
              {
                  //get bookid from Book Details and Employee PIN from current logged-in user
                  bookidTextBox.Text = DetailsView1.SelectedValue.ToString();
                  EmployeeIDTextBox.Text = HttpContext.Current.User.Identity.ToString();
              }
          }
  
          public static void ClearControls(Control Parent)
          {
              if (Parent is TextBox)
              {
                  (Parent as TextBox).Text = string.Empty;
              }
  
              else
              {
                  foreach (Control c in Parent.Controls)
                      ClearControls(c);
              }
          }
      }
  }
  </code></pre>