Add eventhandler dynamically

Question

I'm dynamically adding an event handler on a link button, first when the page is load o create a link button with product category. On clicking the product category it fires an event and passes the product-id IN sender object.

Here is my problem: when i readd the event handler on page load it's giving an error cannot cast sender object

code:

sub page int

Me.Page.EnableViewState = True

end sub

---

page load

 CatDisplay()

  If ViewState("GetProductClicked") = True Then

GetProduct(Me, New EventArgs)

    End If

---

Function CatDisplay() As Boolean
        Dim arr As New ArrayList
        Dim objTesting As New Bo_Dall_Layer.BoCategory
        arr = objTesting.GetAllCategory()

        Dim objExtra As Bo_Dall_Layer.BoCategory
        Dim Cat_hyperLink As LinkButton

        For Each objExtra In arr

            Cat_hyperLink = New LinkButton
            Cat_hyperLink.Text = objExtra.CategoryName
            Cat_hyperLink.CommandArgument = objExtra.CategoryId

            AddHandler Cat_hyperLink.Click, AddressOf GetProduct

            CatPanel.Controls.Add(New LiteralControl("<br />"))
            CatPanel.Controls.Add(Cat_hyperLink)
        Next



        ViewState.Item("CategoryLoaded") = False.ToString

    End Function


    Private Sub GetProduct(ByVal sender As Object, ByVal e As EventArgs)

        Dim arrCollectList As New ArrayList
        Dim getLinkDetail As LinkButton = CType(sender, LinkButton)
        Dim getCatID As String = getLinkDetail.CommandArgument
        Dim SendCatID As Integer
        SendCatID = CInt(getCatID)
        Dim objGetProduct As New Bo_Dall_Layer.BoProduct
        arrCollectList = objGetProduct.getSelectProduct(SendCatID)
        Dim objTemCollectPrd As Bo_Dall_Layer.BoProduct

        Dim lblPrdName As Label
        Dim lblPrdDes As Label
        Dim lblPrdPrice As Label
        Dim addCart As LinkButton


        For Each objTemCollectPrd In arrCollectList

            lblPrdName = New Label
            lblPrdDes = New Label
            lblPrdPrice = New Label
            addCart = New LinkButton

            getCatID = objTemCollectPrd.ProductId

            PrdName.Controls.Add(New LiteralControl("<br />"))
            lblPrdName.Text = objTemCollectPrd.ProductName
            PrdName.Controls.Add(New LiteralControl("<br />"))

            PrdDesc.Controls.Add(New LiteralControl("<br />"))
            lblPrdDes.Text = objTemCollectPrd.ProductDescription
            PrdDesc.Controls.Add(New LiteralControl("<br />"))
            lblPrdPrice.Text = objTemCollectPrd.ProductPrice

            PrdPrice.Controls.Add(New LiteralControl("<br />"))
            lblPrdPrice.Text = objTemCollectPrd.ProductPrice
            PrdPrice.Controls.Add(New LiteralControl("<br />"))

            PrdCart.Controls.Add(New LiteralControl("<br />"))
            addCart.Text = "Add to Cart"
            addCart.CommandArgument = objTemCollectPrd.ProductId
            PrdCart.Controls.Add(New LiteralControl("<br />"))


            PrdName.Controls.Add(lblPrdName)
            PrdDesc.Controls.Add(lblPrdDes)
            PrdPrice.Controls.Add(lblPrdPrice)
            PrdCart.Controls.Add(addCart)
        Next

        ViewState.Item("GetProductClicked") = True


    End Sub

when the page is reload it giving me an error

Unable to cast object of type 'ASP.products_aspx' to type 'System.Web.UI.WebControls.LinkButton' Dim getLinkDetail As LinkButton = CType(sender, LinkButton)

Answer 1

in the line GetProduct(Me, New EventArgs) you are passing in a reference to the page (Me) as the sender parameter. In the GetProduct method with this line Dim getLinkDetail As LinkButton = CType(sender, LinkButton) you are trying to cast the page as a link button. You are not assigning an event handler in the page load method at all, you are just calling the method.