Hi,

I have following code to make a shopping cart and when I run it I get an error saying "Object reference not set to an instance of an object" and the error is in this line,

VB Code:
  1. "Line 51:         For Each objDR In objDT.Rows"
Its the line in SUB AddToCart...

VB Code:
  1. Private objDT As System.Data.DataTable

  2.     Private objDR As System.Data.DataRow

  3.  
  4.     Private Sub Page_Load(ByVal s As Object, ByVal e As EventArgs)

  5.         If Not IsPostBack Then

  6.             makeCart()

  7.         End If

  8.     End Sub

  9.  
  10.     Function makeCart()

  11.         objDT = New System.Data.DataTable("Cart")

  12.         objDT.Columns.Add("ID", GetType(Integer))

  13.         objDT.Columns("ID").AutoIncrement = True

  14.         objDT.Columns("ID").AutoIncrementSeed = 1

  15.  
  16.         objDT.Columns.Add("Quantity", GetType(Integer))

  17.         objDT.Columns.Add("Product", GetType(String))

  18.         objDT.Columns.Add("Cost", GetType(Decimal))

  19.  
  20.         Session("Cart") = objDT

  21.     End Function

  22.  
  23.     Sub AddToCart(ByVal s As Object, ByVal e As EventArgs)

  24.         objDT = Session("Cart")

  25.         Dim Product = ddlProducts.SelectedItem.Text

  26.         Dim blnMatch As Boolean = False

  27.  
  28.         For Each objDR In objDT.Rows

  29.             If objDR("Product") = Product Then

  30.                 objDR("Quantity") += txtQuantity.Text

  31.                 blnMatch = True

  32.                 Exit For

  33.             End If

  34.         Next

  35.  
  36.         If Not blnMatch Then

  37.             objDR = objDT.NewRow

  38.             objDR("Quantity") = txtQuantity.Text

  39.             objDR("Product") = ddlProducts.SelectedItem.Text

  40.             objDR("Cost") = Decimal.Parse(ddlProducts.SelectedItem.Value)

  41.             objDT.Rows.Add(objDR)

  42.         End If

  43.         Session("Cart") = objDT

  44.  
  45.         dg.DataSource = objDT

  46.         dg.DataBind()

  47.  
  48.         lblTotal.Text = "$" & GetItemTotal()

  49.     End Sub

  50.  
  51.     Function GetItemTotal() As Decimal

  52.         Dim intCounter As Integer

  53.         Dim decRunningTotal As Decimal

  54.  
  55.         For intCounter = 0 To objDT.Rows.Count - 1

  56.             objDR = objDT.Rows(intCounter)

  57.             decRunningTotal += (objDR("Cost") * objDR("Quantity"))

  58.         Next

  59.  
  60.         Return decRunningTotal

  61.     End Function

  62.  
  63.     Sub Delete_Item(ByVal s As Object, ByVal e As DataGridCommandEventArgs)

  64.         objDT = Session("Cart")

  65.         objDT.Rows(e.Item.ItemIndex).Delete()

  66.         Session("Cart") = objDT

  67.  
  68.         dg.DataSource = objDT

  69.         dg.DataBind()

  70.  
  71.         lblTotal.Text = "$" & GetItemTotal()

  72.     End Sub

Can anyone tell me how to create an object of this type...???

Cheers...