Asp.net cannot convert type 'string' to System.Data.DataRowView"

Question

I am very new to asp.net c# I have a bit of a problem and hoping someone could help me out please.

What I would like to do is auto-fill some text boxes in asp.net using c# from a drop down list so when they click on the list and select the retails the text boxes will auto populate with the matching information from the Access Data Base

Below is my code so far it is a bit of a mess but that is because I am still writing it.

namespace ChocoMamboAsp
{
    public partial class  SalesOrderForm : System.Web.UI.UserControl
    {
        SalesOrder _order = null;


        protected void Page_Load(object sender, EventArgs e)
        {
            if (System.Web.HttpContext.Current.Session["SalesOrderID"] == null)
            {
                _order = new SalesOrder();
                populateCustomerCombo();
                populateEmployeeCombo();
                populateProductCombo();

            }
            else
            {
                _order = new SalesOrder(long.Parse(System.Web.HttpContext.Current.Session["SalesOrderID"].ToString()));
                populateCustomerCombo();
                populateEmployeeCombo();
                populateProductCombo();

                displayRecord();


           }

        }

        #region Mutators
        /// <summary>
        /// Pre-Condtion:   Event Call
        /// Post-Condition: calculates the item total
        /// Description:    Calculates the line total for each item in the grid list
        /// </summary>
        private void calculateLineTotal()
        {
            int intQty = 0;
            decimal decPrice = 0.0M;
            var total = 0;
            foreach (GridViewRow row in dgvOrderLine.Rows)
            {
                var numberLabel = row.FindControl("LineTotal") as Label;
                int number;
                if (int.TryParse(numberLabel.Text, out number))
                {
                    total += number;
                }
            }

            decimal decLineTotal = decPrice * intQty;
            txtSubTotal.Text = decLineTotal.ToString("c2");
            calculateGrandTotal();
        }

        /// <summary>
        /// Pre-Condtion:   Events call
        /// Post-Condition: Calculate the total of all the items
        /// Description:    This will calculate the total of all the items in the list area.
        /// </summary>
        private void calculateGrandTotal()
        {
            try
            {
                decimal decGrandTotal = decimal.Parse(_order.getOrderLinesTable().Compute
                                                      ("Sum(LineTotal)", "").ToString());
                lblTotal.Text = decGrandTotal.ToString("c2");
            }
            catch (FormatException)
            {
                //this exception will occur if tblOrderLine is empty which we can safely ignore
            }
        }


        #endregion

        protected void btnInsert_Click(object sender, EventArgs e)
        {

                assignChildData();
                _order.OrderLineClass.addNewRecord();
                calculateGrandTotal();
                emptyControls();

        }

        #region Accessors
        /// <summary>
        /// Pre-Condition: Second Constructor Call 
        /// Post-Condition: Gettes the information from the class getters and setters 
        /// Description: This method gets all the information relating to the table database that has been used.
        /// </summary>     
        private void displayRecord()
        {
            cboRetailer.SelectedValue = _order.RetailerID.ToString();
            dtpSalesOrder.Text = _order.SalesDate.ToString();
            cboSalesAgent.SelectedValue = _order.EmployeeID.ToString();
            txtRetailerAddress.Text = _order.RetailerAddress;
            txtRetailerPhone.Text = _order.RetailerPhone;
            lblTotal.Text = _order.SaleTotal.ToString("c2");
            dgvOrderLine.DataSource = _order.getOrderLinesTable();
            dgvOrderLine.DataBind();

            System.Diagnostics.Debug.WriteLine(_order.getOrderLinesTable());
        }
        /// <summary>
        /// Pre-Condition:  Construtor's call
        /// Post-Condition:Populates the combo box with the requested information
        /// Description: This method uses the method from the class in order to populate the combo box with the selcted information
        ///              To display one or more Items.
        /// </summary>
        private void populateCustomerCombo()
        {
            cboRetailer.DataSource = _order.getCustomers();
            cboRetailer.DataValueField = "RetailerID";
            cboRetailer.DataTextField = "RetailerName";
            cboRetailer.DataBind();

        }
        /// <summary>
        /// Pre-Condition:  Construtor's call
        /// Post-Condition:Populates the combo box with the requested information
        /// Description: This method uses the method from the class in order to populate the combo box with the selcted information
        ///              To display one or more Items.
        /// </summary>
        private void populateEmployeeCombo()
        {
            cboSalesAgent.DataSource = _order.getEmployee();
            cboSalesAgent.DataValueField = "EmployesID";
            cboSalesAgent.DataTextField = "EmployeeFirstName";
            cboSalesAgent.DataBind(); 

        }
        /// <summary>
        /// Pre-Condition:  Construtor's call
        /// Post-Condition:Populates the combo box with the requested information
        /// Description: This method uses the method from the class in order to populate the combo box with the selcted information
        ///              To display one or more Items.
        /// </summary>
        private void populateProductCombo()
        {

            cboProducts.DataSource = _order.getProducts();
            cboProducts.DataTextField = "ProdustsName";
            cboProducts.DataValueField = "ProductsID";
            cboProducts.SelectedIndex = -1;//will make the combo box select nothing
            cboProducts.DataBind();

        }


        /// <summary>
        /// Pre-Condition:  Event method call
        /// Post-Condition: Empties fields
        /// Description:    Method used to empty all the fields
        /// </summary>
        private void emptyTopControls()
        {
            cboSalesAgent.SelectedIndex = -1;
            cboRetailer.SelectedIndex = -1;
            txtRetailerAddress.Text = "";
            txtRetailerPhone.Text = "";
        }

        //mutators
        /// <summary>
        /// Pre-Condition:  Event call Method
        /// Post-Condition: Empties the controls for the lower section
        /// Description:    This will empty the controls of the lower section so the user can in put another item 
        ///                 In side the DataTable of the gridView we are casting the datasource as a data table in order 
        ///                 for us to delete the information inside each of the rows of the data table.
        /// </summary>
        private void emptyControls()
        {
            cboProducts.SelectedIndex = -1;
            txtPrice.Text = "";
            txtQty.Text = "";
            txtSubTotal.Text = string.Empty;
            btnInsert.Enabled = true;
            btnUpdate.Enabled = false;
            dgvOrderLine.DataSource = _order.getOrderLinesTable();
        }
        /// <summary>
        /// Pre-Condtion:   Event Call
        /// Post-Condition: Send information to the list grid
        /// Description:    This method will send the infromation from the selection side into the display list
        /// </summary>
        private void assignChildData()
        {
            _order.OrderLineClass.ProductsID = long.Parse(cboProducts.SelectedValue.ToString());
            _order.OrderLineClass.Qty = long.Parse(txtQty.Text);
            _order.OrderLineClass.Price = decimal.Parse(txtPrice.Text.Substring
                                                          (txtPrice.Text.IndexOf('$') + 1));
            _order.OrderLineClass.SalesOrderID = _order.PKID;
            _order.OrderLineClass.LineTotal = decimal.Parse(txtSubTotal.Text);
            _order.OrderLineClass.ProdustsName = cboProducts.Text;
        }


        /// <summary>
        /// Pre-Condition:  Event Call
        /// Post-Condition: Assings informatin to the text/combo fields
        /// Description:    This is called when ever the fields have information that needs displayed
        /// </summary>
        private void assignData()
        {
            DateTime date = Convert.ToDateTime(dtpSalesOrder.Text);
            _order.RetailerID = long.Parse(cboRetailer.SelectedValue.ToString());
            _order.SalesDate =  date;
            _order.EmployeeID = long.Parse(cboSalesAgent.SelectedValue.ToString());
            _order.RetailerAddress = txtRetailerAddress.Text;
            _order.RetailerPhone = txtRetailerPhone.Text;
            _order.SaleTotal = decimal.Parse(lblTotal.Text.Substring
                                              (lblTotal.Text.IndexOf('$') + 1));
        }
        #endregion

        protected void cboRetailer_SelectedIndexChanged(object sender, EventArgs e)
        {

            DataRowView drvCost = (DataRowView)cboRetailer.SelectedValue;
            txtRetailerAddress.Text = drvCost["RetailerAddress"].ToString();
            txtRetailerPhone.Text = drvCost["RetailerPhone"].ToString();
        }
    }

Answer 1

cboRetailer.SelectedValue is a string, you can't convert it to DataRowView.

You can try something like this:

EDIT:

If getCustomers() returns a datatable, you can do like this:

protected void cboRetailer_SelectedIndexChanged(object sender, EventArgs e)
{
    var dt = _order.getCustomers();

    for (int i = 0; i < dt.Rows.Count; i++)
    {
        if (dt.Rows[i]["RetailerID"].ToString() == cboRetailer.SelectedValue)
        {
            txtRetailerAddress.Text = dt.Rows[i]["RetailerAddress"].ToString();
            txtRetailerPhone.Text = dt.Rows[i]["RetailerPhone"].ToString();

        }
    }

}

Or if getCustomers() returns IEmunerable<Customer>, you can do like this:

protected void cboRetailer_SelectedIndexChanged(object sender, EventArgs e)
{
    int retailerID = 0;
    if(int.TryParse(cboRetailer.SelectedValue, out retailerID) && retailerID > 0)
    {
        var retailer = _order.getCustomers().Where(x => x.RetailerID == retailerID).FirstOrDefault();
        if (retailer != null)
        {
            txtRetailerAddress.Text = retailer.RetailerAddress;
            txtRetailerPhone.Text = retailer.RetailerPhone;
        }
    }
}