ORA-01008: Not all variables bound error when inserting data

I have been having challenges inserting data into an oracle table. Please find attaced my source code. Whenever I click the Save button I get the exception ORA-01008: Not all variables bound. Please note that there is a trigger in the schema that is set to auto increment Trans_ID by 1 whenever a row is to be inserted into the table Request.

I dont know what I am doing wrongly. Please help!

Below is the script for the table

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Data.OracleClient;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class HouseRequest : System.Web.UI.Page
{
    public string connectionstring = System.Configuration.ConfigurationManager.ConnectionStrings["HouseMgtConnectionString"].ConnectionString;
    public static string employeeno;
    public static string lastname;
    public static string firstname;
    public static string middlename;
    public static string email;
    public static string department;
    public static string designation;
    public static string staff_flag;
    public DateTime arrdate;
    public DateTime depdate;

    /*public string employeeno;
    public string lastname;
    public string firstname;
    public string middlename;
    public string email;
    public string department;
    public string designation;
    public string staff_flag;*/

    //Requests xx = new Requests();
    //RequestDAL request = new RequestDAL();

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            ddlBranch.Items.Insert(0, "--Select--");
            ddlHouse.Items.Insert(0, "--Select--");
            ddlFlat.Items.Insert(0, "--Select--");
            ddlRoom.Items.Insert(0, "--Select--");
            FillBranch();

            //FillddlRooms();
            if ((Request.QueryString["param1"] != null && Request.QueryString["param2"] != null) && Request.QueryString["param3"] != null && Request.QueryString["param4"] != null && Request.QueryString["param5"] != null && Request.QueryString["param6"] != null && Request.QueryString["param6"] != null && Request.QueryString["param7"] != null && Request.QueryString["param8"] != null)

            employeeno = Request.QueryString["param1"];
            lastname = Request.QueryString["param2"];
            firstname = Request.QueryString["param3"];
            middlename = Request.QueryString["param4"];
            email = Request.QueryString["param5"];
            department = Request.QueryString["param6"];
            designation = Request.QueryString["param7"];
            staff_flag = Request.QueryString["param8"];

        }

    }

    protected void ddlBranch_SelectedIndexChanged(object sender, EventArgs e)
    {
        ddlHouse.Items.Insert(0, "--Select--");
        string Branch_Code = ddlBranch.SelectedValue.ToString();

        FillHouse(Branch_Code);

    }
    protected void ddlHouse_SelectedIndexChanged(object sender, EventArgs e)
    {

        ddlFlat.Items.Insert(0, "--Select--");
        string House_ID = ddlHouse.SelectedValue.ToString();
        FillFlat(House_ID);

    }

    protected void ddlFlat_SelectedIndexChanged(object sender, EventArgs e)
    {

        ddlRoom.Items.Insert(0, "--Select--");
        string Flat_ID = ddlFlat.SelectedValue.ToString();
        FillRooms(Flat_ID);
    }

    private void FillBranch()
    {
        //string strConn = System.Configuration.ConfigurationManager.ConnectionStrings["HouseMgtConnectionString"].ConnectionString;
        OracleConnection con = new OracleConnection(connectionstring);
        OracleCommand cmd = new OracleCommand();
        cmd.Connection = con;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "SELECT Branch_Code, Description FROM Branch WHERE Status='A'";
        DataSet objDs = new DataSet();
        OracleDataAdapter dAdapter = new OracleDataAdapter();
        dAdapter.SelectCommand = cmd;
        con.Open();
        dAdapter.Fill(objDs);
        con.Close();
        if (objDs.Tables[0].Rows.Count > 0)
        {
            ddlBranch.DataSource = objDs.Tables[0];
            ddlBranch.DataTextField = "Description";
            ddlBranch.DataValueField = "Branch_Code";
            ddlBranch.DataBind();
            ddlBranch.Items.Insert(0, "--Select--");
            lblResults.Text = "";
        }
        else
        {
            lblResults.Text = "No Branch found";
            ddlHouse.Items.Clear();
            ddlFlat.Items.Clear();
            ddlRoom.Items.Clear();

        }
    }

    private void FillHouse(string Branch_Code)
    {
        //string strConn = System.Configuration.ConfigurationManager.ConnectionStrings["HouseMgtConnectionString"].ConnectionString;
        OracleConnection con = new OracleConnection(connectionstring);
        OracleCommand cmd = new OracleCommand();
        cmd.Connection = con;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "SELECT House_ID, Description FROM House WHERE Branch_Code =:Branch_Code AND Status='A'";
        cmd.Parameters.AddWithValue(":Branch_Code", Branch_Code);
        DataSet objDs = new DataSet();
        OracleDataAdapter dAdapter = new OracleDataAdapter();
        dAdapter.SelectCommand = cmd;
        con.Open();
        dAdapter.Fill(objDs);
        con.Close();
        if (objDs.Tables[0].Rows.Count > 0)
        {
            ddlHouse.DataSource = objDs.Tables[0];
            ddlHouse.DataTextField = "Description";
            ddlHouse.DataValueField = "House_ID";
            ddlHouse.DataBind();
            ddlHouse.Items.Insert(0, "--Select--");
            lblResults.Text = "";
        }
        else
        {
            lblResults.Text = "No House found";
            ddlHouse.Items.Clear();
            ddlFlat.Items.Clear();
            ddlRoom.Items.Clear();

        }
    }

    private void FillFlat(string House_ID)
    {
        //string strConn = System.Configuration.ConfigurationManager.ConnectionStrings["HouseMgtConnectionString"].ConnectionString;
        OracleConnection con = new OracleConnection(connectionstring);
        OracleCommand cmd = new OracleCommand();
        cmd.Connection = con;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "SELECT Flat_ID, Flat_No FROM Flats WHERE House_ID =:House_ID AND Status='A'";
        cmd.Parameters.AddWithValue(":House_ID", House_ID);
        DataSet objDs = new DataSet();
        OracleDataAdapter dAdapter = new OracleDataAdapter();
        dAdapter.SelectCommand = cmd;
        con.Open();
        dAdapter.Fill(objDs);
        con.Close();
        if (objDs.Tables[0].Rows.Count > 0)
        {
            ddlFlat.DataSource = null;
            ddlFlat.DataBind();
            ddlFlat.DataSource = objDs.Tables[0];
            ddlFlat.DataTextField = "Flat_No";
            ddlFlat.DataValueField = "Flat_ID";
            ddlFlat.DataBind();
            ddlFlat.Items.Insert(0, "--Select--");
            lblResults.Text = "";
        }
        else
        {
            lblResults.Text = "No Flat found";
            ddlFlat.Items.Clear();
            ddlRoom.Items.Clear();

        }
    }

    private void FillRooms(string Flat_ID)
    {
        //string strConn = System.Configuration.ConfigurationManager.ConnectionStrings["HouseMgtConnectionString"].ConnectionString;
        OracleConnection con = new OracleConnection(connectionstring);
        OracleCommand cmd = new OracleCommand();
        cmd.Connection = con;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "SELECT Room_ID, Room_No FROM Rooms WHERE Flat_ID =:Flat_ID AND Room_Status='0' AND Status='A'";
        cmd.Parameters.AddWithValue(":Flat_ID", Flat_ID);
        DataSet objDs = new DataSet();
        OracleDataAdapter dAdapter = new OracleDataAdapter();
        dAdapter.SelectCommand = cmd;
        con.Open();
        dAdapter.Fill(objDs);
        con.Close();
        if (objDs.Tables[0].Rows.Count > 0)
        {
            ddlRoom.DataSource = objDs.Tables[0];
            ddlRoom.DataTextField = "Room_No";
            ddlRoom.DataValueField = "Room_ID";
            ddlRoom.DataBind();
            ddlRoom.Items.Insert(0, "--Select--");
            lblResults.Text = "";
        }
        else
        {
            lblResults.Text = "No Room found";
            ddlRoom.Items.Clear();

        }
    }

    protected void btnSave_Click(object sender, EventArgs e)
        //(int? Trans_ID, string Emp_No, string Last_Name, string Middle_Name, string First_Name, string E_Mail, string Department_Code, string Job_title, DateTime Trans_Date, string Staff_Flag, string Branch_Code, string Hotel_Code, string House_ID, string Flat_No, string Room_ID, DateTime Arr_Date, string Arr_Time, DateTime Dep_Date, string Dep_Time, string Remarks, string approval, string Usercode, string DSO_UserCode, string HR_UserCode, DateTime LastUpdated)
    {

        arrdate = DateTime.Parse(txtArrivalDate.Text);
        depdate = DateTime.Parse(txtDepDate.Text);
        OracleConnection con = new OracleConnection(connectionstring);

        string InsertSQL = "INSERT INTO Request(Trans_ID, Emp_No, Last_Name, Middle_Name, First_Name, E_Mail, Department_Code, Job_title, Trans_Date, Staff_Flag, Branch_Code, Hotel_Code, House_ID, Flat_No, Room_ID, Arr_Date, Arr_Time, Dep_Date, Dep_Time, Remarks, approval, Usercode, DSO_UserCode, HR_UserCode, LastUpdated)  VALUES(:Trans_Id, :Emp_No, :Last_Name, :Middle_Name, :First_Name, :E_Mail, :Department_Code, :Job_title,:Trans_Date, :Staff_Flag, :Branch_Code, :Hotel_Code, :House_ID, :Flat_No, :Room_ID, :Arr_Date,:Arr_Time, :Dep_Date, :Dep_Time, :Remarks, :approval, :Usercode, :DSO_UserCode, :HR_UserCode, :LastUpdated)";

       

            OracleCommand com = new OracleCommand(InsertSQL, con);

            com.Parameters.AddWithValue(":Trans_Id", null);
            com.Parameters.AddWithValue(":Emp_No", employeeno);
            com.Parameters.AddWithValue(":Last_Name", lastname);
            com.Parameters.AddWithValue(":Middle_Name", middlename);
            com.Parameters.AddWithValue(":First_Name", firstname);
            com.Parameters.AddWithValue(":E_Mail", email);
            com.Parameters.AddWithValue(":Department_Code", department);
            com.Parameters.AddWithValue(":Job_title", designation);
            com.Parameters.AddWithValue(":Trans_Date", DateTime.Now);
            com.Parameters.AddWithValue(":Staff_Flag", staff_flag);
            com.Parameters.AddWithValue(":Branch_Code", ddlBranch.SelectedItem.Value);
            com.Parameters.AddWithValue(":Hotel_Code", "na");
            com.Parameters.AddWithValue(":House_ID", ddlHouse.SelectedItem.Value);
            com.Parameters.AddWithValue(":Flat_No", ddlFlat.SelectedItem.Value);
            com.Parameters.AddWithValue(":Room_ID", ddlRoom.SelectedItem.Value);
            com.Parameters.AddWithValue(":Arr_Date", arrdate);
            com.Parameters.AddWithValue(":Arr_Time", (txtArrivalTime.Text).ToString());
            com.Parameters.AddWithValue(":Dep_Date", depdate);
            com.Parameters.AddWithValue(":Dep_Time", (txtDepTime.Text).ToString());
            com.Parameters.AddWithValue(":Remarks", txtRemarks.Text);
            com.Parameters.AddWithValue(":approval", "na");
            com.Parameters.AddWithValue(":Usercode", User.Identity.Name.ToUpper());
            com.Parameters.AddWithValue(":DSO_UserCode", "na");
            com.Parameters.AddWithValue(":HR_UserCode", "na");
            com.Parameters.AddWithValue(":LastUpdated", DateTime.Now);

int added = 0;

            try
            {
                con.Open();
                com.CommandType = CommandType.Text;
                added= com.ExecuteNonQuery();
                lblResults.Text = added.ToString() + " record inserted.";
       

        }

        catch (System.Data.OracleClient.OracleException ex)
        {
            string msg = "Insert Error:";
            msg += ex.Message;
            throw new Exception(msg);

        }
        finally
        {
            con.Close();
        }
    }

Below is the script for creating the table Request

CREATE TABLE request
(
   Trans_ID         NUMBER(38) NOT NULL,
   Emp_No        VARCHAR2(9),
   Last_Name        VARCHAR2(25) NOT NULL,
   Middle_Name      VARCHAR2(25),
   First_Name       VARCHAR2(25) NOT NULL,
   E_Mail           VARCHAR2(25) NOT NULL,        
   Department_Code  VARCHAR2(7),
   Job_title        VARCHAR2(25),
   Trans_Date       DATE NOT NULL,
   Staff_Flag     CHAR(1) DEFAULT '0',
   Branch_Code      VARCHAR2(7),
   Hotel_Code       VARCHAR2(7),
   House_ID         VARCHAR2(7),
   Flat_No     VARCHAR2(7),
   Room_ID     VARCHAR2(7),
   Arr_Date     DATE,
   Arr_Time       VARCHAR2(8),
   Dep_Date         DATE,
   Dep_Time         VARCHAR2(8),
   Remarks          VARCHAR2(35),
   approval         VARCHAR2(2),
   Usercode         VARCHAR2(20),
   DSO_UserCode     VARCHAR2(20),
   HR_UserCode     VARCHAR2(20),
   LastUpdated      DATE DEFAULT sysdate NOT NULL,
   CONSTRAINT fk_Trans_one FOREIGN KEY(Branch_Code) REFERENCING Branch,
   CONSTRAINT fk_Trans_two FOREIGN KEY(House_ID) REFERENCING House,
   CONSTRAINT fk_Trans_three FOREIGN KEY(Room_ID) REFERENCING Rooms,
   CONSTRAINT fk_Trans_Four FOREIGN KEY(Hotel_Code) REFERENCING Hotels,
   CONSTRAINT fk_Trans_Five FOREIGN KEY(Emp_No) REFERENCING peoplesmandev.employee_master(emp_no),
   CONSTRAINT pk_tran PRIMARY KEY (Trans_ID)
);