hi people! I badly need a help regarding this program.. I want to insert this two data in my database...

try
            {
               
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();

                OleDbCommand ccmd1 = new OleDbCommand("INSERT INTO [ORDER_DRIVER]([DELIVERY_NO],[DRIVER_ID],[STATUS])" + "VALUES(" + "'" + textBox1.Text + "'" + "," + "'" + comboBox4.Text + "'" + "," + "'" + textBox16.Text + "'" + ")", conn);
                ccmd1.ExecuteNonQuery();
                OleDbCommand ccmd2 = new OleDbCommand("INSERT INTO [ORDER_DRIVER]([DELIVERY_NO],[DRIVER_ID],[STATUS])" + "VALUES(" + "'" + textBox1.Text + "'" + "," + "'" + comboBox5.Text + "'" + "," + "'" + textBox17.Text + "'" + ")", conn);
                ccmd2.ExecuteNonQuery();
                conn.Close();
                
            }

but is unable to do that.. what do you think was the problem?
the error was..

you cannot add or change a record because a related record is required in table DRIVER.

---accrdg to connection error. please help... anywasy this is the whole program of my save button. :)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
using System.Data.SqlClient;


namespace C_CONTRUCTS
{
    public partial class ORDER : Form
    {
        public ORDER()
        {
            InitializeComponent();
        }


        private void ORDER_Load(object sender, EventArgs e)
        {
            try
            {///opening of database
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                MessageBox.Show("You are connected to the Database", "Data Connection");
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error in Connection");
            }



            try
            {////combobox of customer ID
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter dac = new OleDbDataAdapter("SELECT * FROM CUSTOMER", conn);
                DataTable ds = new DataTable();
                dac.Fill(ds);
                comboBox1.Text = "Please Select Customer ID";
                for (int i = 1; i < ds.Rows.Count; i++)
                {
                    comboBox1.Items.Add(ds.Rows[i]["CUSTOMER_ID"]);
                }

                conn.Close();
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error in Connection");
            }

            try
            {////combobox of product ID
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter dap = new OleDbDataAdapter("SELECT * FROM PRODUCT", conn);
                DataTable ds = new DataTable();
                dap.Fill(ds);
                comboBox2.Text = "Please Select Product ID";
                for (int a = 1; a < ds.Rows.Count; a++)
                {
                    comboBox2.Items.Add(ds.Rows[a]["PRODUCT_ID"]);
                }

                conn.Close();
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error in Connection");
            }


            try
            {///combobox of truck ID
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter dat = new OleDbDataAdapter("SELECT * FROM TRUCK", conn);
                DataTable ds = new DataTable();
                dat.Fill(ds);
                comboBox3.Text = "Please Select Truck ID";
                for (int i = 1; i < ds.Rows.Count; i++)
                {
                    comboBox3.Items.Add(ds.Rows[i]["TRUCK_ID"]);
                }

                conn.Close();
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error in Connection");
            }


            try
            {///combobox driver 1
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter dad = new OleDbDataAdapter("SELECT * FROM DRIVER ", conn);
                DataTable ds = new DataTable();
                dad.Fill(ds);
                comboBox4.Text = "Please Select Driver ID";
                for (int i = 1; i < ds.Rows.Count; i++)
                {
                    comboBox4.Items.Add(ds.Rows[i]["DRIVER_ID"]);
                }


                conn.Close();
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error in Connection");
            }

            try
            {///combobox driver2
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter dadds = new OleDbDataAdapter("SELECT * FROM DRIVER ", conn);
                DataTable ds = new DataTable();
                dadds.Fill(ds);
                comboBox5.Text = "Please Select Driver ID";
                for (int i = 1; i < ds.Rows.Count; i++)
                {
                    comboBox5.Items.Add(ds.Rows[i]["DRIVER_ID"]);
                }


                conn.Close();
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error in Connection");
            }


        }

        private void button6_Click(object sender, EventArgs e)
        {
            Form1 f = new Form1();
            this.Hide();
            f.ShowDialog();
            this.Close();
        }

        private void comboBox1_SelectedIndexChanged_1(object sender, EventArgs e)
        {
            try
            {
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter dda = new OleDbDataAdapter("SELECT * FROM CUSTOMER WHERE CUSTOMER_ID=" + "'" + comboBox1.Text + "'", conn);
                DataSet ddsa = new DataSet();
                dda.Fill(ddsa);
                dataGridView2.DataSource = ddsa.Tables[0].DefaultView;
                DataView dv = (DataView)dataGridView2.DataSource;
                if (dv.Count > 0)
                {
                    textBox2.Text = dv[0]["CUST_COMPANY"].ToString();
                    textBox3.Text = dv[0]["CUST_FNAME"].ToString();
                    textBox4.Text = dv[0]["CUST_MNAME"].ToString();
                    textBox5.Text = dv[0]["CUST_LNAME"].ToString();


                }
                else
                {
                    MessageBox.Show("No Reocrd hs been found", "Record Access");
                }
                conn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.GetBaseException().ToString(), "teka parang may mali?");
            }
        }

        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            try
            {
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter pdaa = new OleDbDataAdapter("SELECT * FROM PRODUCT WHERE PRODUCT_ID=" + "'" + comboBox2.Text + "'", conn);
                DataSet pdss = new DataSet();
                pdaa.Fill(pdss);
                dataGridView2.DataSource = pdss.Tables[0].DefaultView;
                DataView dv = (DataView)dataGridView2.DataSource;
                if (dv.Count > 0)
                {
                    textBox6.Text = dv[0]["PRODUCT_DESC"].ToString();
                }
                else
                {
                    MessageBox.Show("No Reocrd hs been found", "Append");
                }
                conn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.GetBaseException().ToString(), "Append");
            }

        }

        private void comboBox3_SelectedIndexChanged(object sender, EventArgs e)
        {
            try
            {
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();
                OleDbDataAdapter tdaa = new OleDbDataAdapter("SELECT * FROM TRUCK WHERE TRUCK_ID=" + "'" + comboBox3.Text + "'", conn);
                DataSet tdss = new DataSet();
                tdaa.Fill(tdss);
                dataGridView2.DataSource = tdss.Tables[0].DefaultView;
                DataView dv = (DataView)dataGridView2.DataSource;
                if (dv.Count > 0)
                {
                    textBox7.Text = dv[0]["TRUCK_TYPE"].ToString();
                    textBox8.Text = dv[0]["PLATE_NO"].ToString();
                }
                else
                {
                    MessageBox.Show("No Reocrd hs been found", "Append");
                }
                conn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.GetBaseException().ToString(), "teka parang may mali?");
            }

        }

        private void comboBox4_SelectedIndexChanged(object sender, EventArgs e)
        {


         

        }

        private void comboBox4_SelectedIndexChanged_1(object sender, EventArgs e)
        {
            if (comboBox4.Text == comboBox5.Text)
            {
                MessageBox.Show("You already choose that driver!", "Choosing error!");
            }
            else
            {
                try
                {
                    OleDbConnection conn = new OleDbConnection();
                    conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                    conn.Open();
                    OleDbDataAdapter dda = new OleDbDataAdapter("SELECT * FROM DRIVER WHERE DRIVER_ID=" + "'" + comboBox4.Text + "'", conn);
                    DataSet ddsa = new DataSet();
                    dda.Fill(ddsa);
                    dataGridView2.DataSource = ddsa.Tables[0].DefaultView;
                    DataView dv = (DataView)dataGridView2.DataSource;
                    if (dv.Count > 0)
                    {
                        textBox14.Text = dv[0]["DRIVER_FNAME"].ToString();
                        textBox15.Text = dv[0]["DRIVER_LNAME"].ToString();
                    }
                    else
                    {
                        MessageBox.Show("No Reocrd hs been found", "Record Access");
                    }
                    conn.Close();
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.GetBaseException().ToString(), "teka parang may mali?");
                }
            }
        }

        private void comboBox5_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBox4.Text == comboBox5.Text)
            {
                MessageBox.Show("You already choose that driver!", "Choosing error!");
            }
            else
            {
                try
                {
                    OleDbConnection conn = new OleDbConnection();
                    conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                    conn.Open();
                    OleDbDataAdapter dda = new OleDbDataAdapter("SELECT * FROM DRIVER WHERE DRIVER_ID=" + "'" + comboBox5.Text + "'", conn);
                    DataSet ddsa = new DataSet();
                    dda.Fill(ddsa);
                    dataGridView2.DataSource = ddsa.Tables[0].DefaultView;
                    DataView dv = (DataView)dataGridView2.DataSource;
                    if (dv.Count > 0)
                    {
                        textBox19.Text = dv[0]["DRIVER_FNAME"].ToString();
                        textBox18.Text = dv[0]["DRIVER_LNAME"].ToString();
                    }
                    else
                    {
                        MessageBox.Show("No Reocrd hs been found", "Record Access");
                    }
                    conn.Close();
                }

                catch (Exception ex)
                {
                    MessageBox.Show(ex.GetBaseException().ToString(), "teka parang may mali?");
                }
            }
        }

        private void button4_Click(object sender, EventArgs e)
        {

        }

        private void button3_Click(object sender, EventArgs e)
        {
            try
            {


                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();

                DateTime d = DateTime.Today;
                OleDbCommand ccmd = new OleDbCommand("INSERT INTO [ORDER]([DELIVERY_NO],[CUSTOMER_ID],[ODER_INDATE],[TOTAL_AMOUNT],[DR_LENGTH],[DR_WIDTH],[DR_HEIGHT],[DR_RECEIVED_BY],[DR_STREET],[DR_CITY],[DR_ZIPCODE],[TRUCK_ID],[PRODUCT_ID],[PAYMENT_TYPE])" + "VALUES(" + "'" + textBox1.Text + "'" + "," + "'" + comboBox1.Text + "'" + "," + "'" + DateTime.Today + "'" + "," + "'" + textBox9.Text + "'" + "," + "'" + textBox11.Text + "'" + "," + "'" + textBox12.Text + "'" + "," + "'" + textBox10.Text + "'" + "," + "'" + textBox13.Text + "'" + "," + "'" + textBox22.Text + "'" + "," + "'" + textBox21.Text + "'" + "," + "'" + textBox20.Text + "'" + "," + "'" + comboBox3.Text + "'" + "," + "'" + comboBox2.Text + "'" + "," + "'" + textBox23.Text + "'" + ")", conn);
                ccmd.ExecuteNonQuery();

                MessageBox.Show("Order has been successfully saved. ", "Record Added");
                textBox1.Clear();
                textBox2.Clear();
                textBox3.Clear();
                textBox4.Clear();
                textBox5.Clear();
                textBox6.Clear();
                textBox7.Clear();
                textBox8.Clear();
                textBox9.Clear();
                textBox10.Clear();
                textBox11.Clear();
                textBox12.Clear();
                textBox13.Clear();
                textBox14.Clear();
                textBox15.Clear();
                textBox16.Clear();
                textBox17.Clear();
                textBox18.Clear();
                textBox19.Clear();
                textBox20.Clear();
                textBox21.Clear();
                textBox22.Clear();
                textBox23.Clear();
                comboBox1.Text = "Please Select Customer ID";
                comboBox2.Text = "Please Select Product ID";
                comboBox3.Text = "Please Select Truck ID";
                comboBox4.Text = "Please Select Driver ID";
                comboBox5.Text = "Please Select Driver ID";
                conn.Close();
            }
           catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Connection in Error");
            }
////////////////
            try
            {
               
                OleDbConnection conn = new OleDbConnection();
                conn.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\lenovo\Desktop\C CONTRUCTS\C CONTRUCTS\CONSTRUCTION.accdb";
                conn.Open();

                OleDbCommand ccmd1 = new OleDbCommand("INSERT INTO [ORDER_DRIVER]([DELIVERY_NO],[DRIVER_ID],[STATUS])" + "VALUES(" + "'" + textBox1.Text + "'" + "," + "'" + comboBox4.Text + "'" + "," + "'" + textBox16.Text + "'" + ")", conn);
                ccmd1.ExecuteNonQuery();
                OleDbCommand ccmd2 = new OleDbCommand("INSERT INTO [ORDER_DRIVER]([DELIVERY_NO],[DRIVER_ID],[STATUS])" + "VALUES(" + "'" + textBox1.Text + "'" + "," + "'" + comboBox5.Text + "'" + "," + "'" + textBox17.Text + "'" + ")", conn);
                ccmd2.ExecuteNonQuery();
                conn.Close();
                
            }

            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Connection in Error");
            }    
        }

        private void button2_Click(object sender, EventArgs e)
        {
            MessageBox.Show("You may now Add another transaction :) ", "gora na!");
            textBox1.Clear();
            textBox2.Clear();
            textBox3.Clear();
            textBox4.Clear();
            textBox5.Clear();
            textBox6.Clear();
            textBox7.Clear();
            textBox8.Clear();
            textBox9.Clear();
            textBox10.Clear();
            textBox11.Clear();
            textBox12.Clear();
            textBox13.Clear();
            textBox14.Clear();
            textBox15.Clear();
            textBox16.Clear();
            textBox17.Clear();
            textBox18.Clear();
            textBox19.Clear();
            textBox20.Clear();
            textBox21.Clear();
            textBox22.Clear();
            textBox23.Clear();
            comboBox1.Text = "Please Select Customer ID";
            comboBox2.Text = "Please Select Product ID";
            comboBox3.Text = "Please Select Truck ID";
            comboBox4.Text = "Please Select Driver ID";
            comboBox5.Text = "Please Select Driver ID";
        }
        

    }
}

You have a foreign key constraint on the table and there is no record of the key you are trying to insert. In other words, one of the columns in ORDER_DRIVER is a foreign key in Driver, and the value you are putting in ORDER_DRIVER doesn't exist in Driver.

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