System.Data.OleDb.OleDbException - vb.net

Question

I'm trying to connect to .accdb access 2010 database.
I'm getting this:
An unhandled exception of type 'System.Data.OleDb.OleDbException' occurred in System.Data.dll
Additional information: Data type mismatch in criteria expression.
But I don't know where and what the problem is. What should I do?
This is my code:
Private Sub frm_ViewsOrder_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
cmb_order.DataSource = get_data("SELECT DISTINCT fld_order_no FROM tbl_order")
cmb_order.DisplayMember = "fld_order_no"
End Sub
Private Sub refresh_grid(orderid As String)
grd_view.DataSource = get_data("SELECT fld_product_name, fld_bil, fld_price, fld_bil * fld_price as Total FROM tbl_products, tbl_order WHERE tbl_order.fld_product_id = tbl_products.fld_product_id AND tbl_order.fld_order_no = """ & orderid & """ ")
grd_view.Columns(0).HeaderText = "Product Name"
grd_view.Columns(1).HeaderText = "Quantity"
grd_view.Columns(2).HeaderText = "Unit Price (RM)"
grd_view.Columns(3).HeaderText = "Amount(RM)"
grd_view.Columns(2).DefaultCellStyle.Format = "N2"
grd_view.Columns(3).DefaultCellStyle.Format = "N2"
Dim totalValue As Decimal
For Each dgvRow As DataGridViewRow In grd_view.Rows
If Not dgvRow.IsNewRow Then
totalValue += CDec(dgvRow.Cells(3).Value)
End If
Next
txt_total.Text = String.Format("{0:n2}", totalValue)
End Sub

Answer 1

In your SQL I would check that "fld_bil" and "fld_price" are both numeric (like you're not multiplying two string's that have numbers in them together). I would also make sure that "fld_order_no" and your local variable "ordered" are numeric. The type exception from OLEDB makes me think it's a conversion error in the SQL.
Also, you probably want to parameterize your query to prevent SQL injection exploits. It's very easy to do. In your command object (which is presumably in your get_data method) you would want to do something like this:
cmd.CommandText = "SELECT fld_product_name, fld_bil, fld_price, fld_bil * fld_price as Total FROM tbl_products, tbl_order WHERE tbl_order.fld_product_id = tbl_products.fld_product_id AND tbl_order.fld_order_no = #orderid"
' ordered being your local variable
cmd.Parameters.AddWithValue("#orderid", orderid)
This will help prevent anyone from tacting on SQL to the end of your query. Here is a link with a more in depth parameterized query example in VB.Net:
http://www.blakepell.com/2012-02-28-vbnet-parameterized-query-example-and-why-you-should-care