Error in displaying MS Access Database in C#

Question

I think I'm know here as a person who doesn't include a lot of details which I'm sorry about so this time I'll try to be more informative with my problem.

Note: If you're asking why I'm not using exception handle it's because I wanted to work with the codes before handling the exceptions.

As of recent we were taught using MS Access to create a basic databases. So my problem is this. Using this code to display my Database to my listView:

private void Form1_Load(object sender, EventArgs e)
    {
        DataSet ds = new DataSet();
        System.Data.OleDb.OleDbConnection con = new System.Data.OleDb.OleDbConnection("Provider=Microsoft.ACE.Oledb.12.0;Data Source =AssetManagement.accdb");//accessItems is the database file 
        System.Data.OleDb.OleDbDataAdapter adpt = new System.Data.OleDb.OleDbDataAdapter("select * from tbl_Assets", con); 
        adpt.Fill(ds); 
        DataTable table = ds.Tables[0];

        foreach (DataRow row in table.Rows)
        {
            lstViewListOfRooms.Items.Add(row[1].ToString()).SubItems.Add(row[2].ToString());
            for (int i = 0; i < lstViewListOfRooms.Items.Count; i++)
            {
                lstViewListOfRooms.Items[i].SubItems.Add(row[3].ToString());
                lstViewListOfRooms.Items[i].SubItems.Add(row[4].ToString());
            }
        }

and this for adding new items for my database from a different form:

private void btnSaveAddAsset_Click(object sender, EventArgs e)
    {


        if (txtAddFloor.Text == "" || txtAddRoom.Text == "" || string.IsNullOrWhiteSpace(txtAddFloor.Text) == true || string.IsNullOrWhiteSpace(txtAddRoom.Text) == true)
        {
            MessageBox.Show("Please enter valid information", "", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
        }
        else
        {
            ths.lstViewListOfRooms.Items.Add(txtAddFloor.Text).SubItems.Add(txtAddRoom.Text);
            for (int i = 0; i < ths.lstViewListOfRooms.Items.Count; i++)
            {
                String date = "dd/MM/yyyy - HH:mm:ss";
                ths.lstViewListOfRooms.Items[i].SubItems.Add(txtAddDescriptionDetail.Text);
                ths.lstViewListOfRooms.Items[i].SubItems.Add(DateTime.Now.ToString(date));
                con = new OleDbConnection("Provider=Microsoft.ACE.Oledb.12.0;Data Source =AssetManagement.accdb");
                Ds = new DataSet();

                string query = "INSERT INTO tbl_Assets(asset_floor, asset_room, asset_description, asset_createdOn)" + " VALUES (" + txtAddFloor.Text + "," + txtAddRoom.Text + ", '" + txtAddDescriptionDetail.Text + "' , '" + DateTime.Now.ToString(date) + "'" + ") ";
                con.Open();
                Da = new OleDbDataAdapter(query, con);
                Da.Fill(Ds, "tbl_Assets");
                con.Close();
                this.Close();
            }
        }
    }

The problem: Each time I add an item it doesn't just add one but more, every time I add it multiples even more and more. As you can see in this screenshot:

Answer 1

Each time you save, you are adding again every existing room because of this code: for (int i = 0; i < ths.lstViewListOfRooms.Items.Count; i++)

You should insert only new ones and update (if needed) the existing ones. This code will do this:

private void btnSaveAddAsset_Click(object sender, EventArgs e)
{
    if (txtAddFloor.Text == "" || txtAddRoom.Text == "" || string.IsNullOrWhiteSpace(txtAddFloor.Text) == true || string.IsNullOrWhiteSpace(txtAddRoom.Text) == true)
    {
        MessageBox.Show("Please enter valid information", "", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
    }
    else
    {
        ths.lstViewListOfRooms.Items.Add(txtAddFloor.Text).SubItems.Add(txtAddRoom.Text);

        String date = "dd/MM/yyyy - HH:mm:ss";
        ths.lstViewListOfRooms.Items[lstViewListOfRooms.Items.Count - 1].SubItems.Add(txtAddDescriptionDetail.Text);
        ths.lstViewListOfRooms.Items[lstViewListOfRooms.Items.Count - 1].SubItems.Add(DateTime.Now.ToString(date));
        con = new OleDbConnection("Provider=Microsoft.ACE.Oledb.12.0;Data Source =AssetManagement.accdb");
        Ds = new DataSet();

        string query = "INSERT INTO tbl_Assets(asset_floor, asset_room, asset_description, asset_createdOn)" + " VALUES (" + txtAddFloor.Text + "," + txtAddRoom.Text + ", '" + txtAddDescriptionDetail.Text + "' , '" + DateTime.Now.ToString(date) + "'" + ") ";
        con.Open();
        Da = new OleDbDataAdapter(query, con);
        Da.Fill(Ds, "tbl_Assets");
        con.Close();
        this.Close();

    }
}