I faced with funny situation. I created a page which is having some value, I set these value and control my post back event also. The problem is happening when I change a component index(ex reselect a combobox which is not inside my datagrid) then I dont know why without my page call the Page_Load it goes to create a new row in grid function and all of my parameter are null! I am just receiving null exception.

So in other word I try to explain the situation: when I load my page I am initializing some parameter. then everything is working fine. in my page when I change selected item of my combo box, page suppose to go and run function related to that combo box, and call page_load, but it is not going there and it goes to rowcreated function.

I am trying to illustrate part of my page. Please help me because I am not receiving any error except null exception and it triger wrong even which seems so complicated for me.

public partial class W_CM_FRM_02 : System.Web.UI.Page
{
   protected void Page_Load(object sender, EventArgs e)
    {
      if (Page.IsPostBack && !loginFail)
            return;
        InitializeItems();
    }
}

   private void InitializeItems()
    {
    cols = new string[] { "v_classification_code", "v_classification_name" };
        arrlstCMMM_CLASSIFICATION = (ArrayList)db.Select(cols, "CMMM_CLASSIFICATION", "v_classification_code <> 'N'", " ORDER BY v_classification_name");
      }

     }

   protected void DGV_RFA_DETAILS_RowCreated(object sender, GridViewRowEventArgs e)
    {
     //db = (Database)Session["oCon"];
        foreach (DataRow dr in arrlstCMMM_CLASSIFICATION)
            ((DropDownList)DGV_RFA_DETAILS.Rows[index].Cells[4].FindControl("OV_RFA_CLASSIFICATION")).Items.Add(new ListItem(dr["v_classification_name"].ToString(), dr["v_classification_code"].ToString()));
}

 protected void V_CUSTOMER_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (V_CUSTOMER.SelectedValue == "xxx" || V_CUSTOMER.SelectedValue == "ddd")
            V_IMPACTED_FUNCTIONS.Enabled = true;
    }

}

my form:

<%@ Page Language="C#" MasterPageFile="~/MasterPage.master" 
AutoEventWireup="true" CodeFile="W_CM_FRM_02.aspx.cs" 
Inherits="W_CM_FRM_02" Title="W_CM_FRM_02" enableeventvalidation="false" EnableViewState="true"%>
  <td>Project name*</td>        
        <td><asp:DropDownList ID="V_CUSTOMER" runat="server" AutoPostBack="True" 
                onselectedindexchanged="V_CUSTOMER_SelectedIndexChanged"  /></td>
 <td colspan = "8">
        <asp:GridView ID="DGV_RFA_DETAILS" runat="server" ShowFooter="True" AutoGenerateColumns="False"
            CellPadding="1" ForeColor="#333333" GridLines="None" OnRowDeleting="grvRFADetails_RowDeleting"
            Width="100%" Style="text-align: left" 
            onrowcreated="DGV_RFA_DETAILS_RowCreated">
        <RowStyle BackColor="#FFFBD6" ForeColor="#333333" />
            <Columns>
                <asp:BoundField DataField="ON_RowNumber" HeaderText="SNo" />
                <asp:TemplateField HeaderText="RFA/RAD/Ticket No*">
                    <ItemTemplate>
                        <asp:TextBox ID="OV_RFA_NO" runat="server"  Width="120"></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>