showing/hiding a row in the master-detail grid depending on selection of drop down list TELERIK - vb.net

Question

Required system: i'm trying to create a master detail grid in telerik where if the user changes his/her selection on a drop down list in the master grid, the row underneath his/her current row in the details grid appears, and if his/her selection changes again it would disappear.
background information: this system was designed to allow the end user (petrol station auditor) to inspect petrol station, and if he/she happens to find a violation he/she would immediately identify what action should be taken.i've decided to create a checklist with a drop down menu where if the user finds a violation he/she would change the drop down list appears and the procedure that has to be performed due to the violation is shown.
problem: i'm trying to create an event using selectedindexchanged in the master grid depending on the drop down list selection. if the dropdown list selection is "in violation" the row would appear in the details grid, otherwise it would disappear. the value i'm using to map the master-details rows to each other is called "SRS".
when trying to obtain the row index with variable "rowIndex", i find an error regarding a type change from one type to another performing my typecasting. i've tried rigorously to solve the issue with no results.
i would be very grateful if someone could provide the code to resolve my issue
NOTE: i will highlight the problematic line of code
vb code (problematic code):
Protected Sub SqlDataSource_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceSelectingEventArgs) Handles SqlDataSource.Selecting
End Sub
Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
**PROBLEMATIC LINE** ------------------------> Dim rowIndex As Integer = CType(CType(sender, RadDropDownList).Parent.Parent, GridViewRow).RowIndex
Dim SRSText As String = RadGrid1.MasterTableView.Items(rowIndex).Cells(3).Text
If sender.SelectedValue = "in violation" Then
SqlDataSource1.SelectParameters.Add(":SRSText", SRSText)
RadGrid1.MasterTableView.DetailTables(0).DataSource = SqlDataSource1
RadGrid1.MasterTableView.DetailTables(0).DataBind()
Else
End If
End Sub
End Class
accompanying ASPX code, for further information:
<%# Page Title="" Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false"
CodeFile="Default.aspx.vb" Inherits="_Default" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
<telerik:RadScriptManager ID="RadScriptManager1" runat="server">
<Scripts>
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js">
</asp:ScriptReference>
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQuery.js">
</asp:ScriptReference>
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQueryInclude.js">
</asp:ScriptReference>
</Scripts>
</telerik:RadScriptManager>
<telerik:RadStyleSheetManager ID="RadStyleSheetManager1" runat="server">
</telerik:RadStyleSheetManager>
<telerik:RadTextBox ID="RadTextBox1" runat="server" AutoPostBack="True" LabelWidth="64px"
Resize="None" Text="please enter the PFS number" Width="160px">
</telerik:RadTextBox>
<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server">
</telerik:RadAjaxManager>
<asp:SqlDataSource ID="SqlDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>" SelectCommand="SELECT * FROM "CHECKLIST"">
</asp:SqlDataSource>
<p>
</p>
<telerik:RadGrid ID="RadGrid1" runat="server" CellSpacing="0" DataSourceID="SqlDataSource"
GridLines="None" AllowMultiRowSelection="True" AutoGenerateColumns="False">
<ExportSettings>
<Pdf>
<PageHeader>
<LeftCell Text=""></LeftCell>
<MiddleCell Text=""></MiddleCell>
<RightCell Text=""></RightCell>
</PageHeader>
<PageFooter>
<LeftCell Text=""></LeftCell>
<MiddleCell Text=""></MiddleCell>
<RightCell Text=""></RightCell>
</PageFooter>
</Pdf>
</ExportSettings>
<ClientSettings EnablePostBackOnRowClick="True" EnableRowHoverStyle="True">
<Selecting AllowRowSelect="True" />
</ClientSettings>
<MasterTableView DataKeyNames="INSPECTIONNO" DataSourceID="SqlDataSource">
<CommandItemSettings ExportToPdfText="Export to PDF"></CommandItemSettings>
<RowIndicatorColumn Visible="True" FilterControlAltText="Filter RowIndicator column">
<HeaderStyle Width="20px"></HeaderStyle>
</RowIndicatorColumn>
<ExpandCollapseColumn Visible="True" FilterControlAltText="Filter ExpandColumn column">
<HeaderStyle Width="20px"></HeaderStyle>
</ExpandCollapseColumn>
<DetailTables>
<telerik:GridTableView AutoGenerateColumns="false" DataSourceID="SqlDataSource1"
Width="100%">
<CommandItemSettings ExportToPdfText="Export to PDF"></CommandItemSettings>
<ParentTableRelation>
<telerik:GridRelationFields DetailKeyField="SRS" MasterKeyField="SRS"></telerik:GridRelationFields>
</ParentTableRelation>
<RowIndicatorColumn Visible="True" FilterControlAltText="Filter RowIndicator column"></RowIndicatorColumn>
<ExpandCollapseColumn Visible="True" FilterControlAltText="Filter ExpandColumn column"></ExpandCollapseColumn>
<EditFormSettings>
<EditColumn FilterControlAltText="Filter EditCommandColumn column"></EditColumn>
</EditFormSettings>
<BatchEditingSettings EditType="Cell"></BatchEditingSettings>
<PagerStyle PageSizeControlType="RadComboBox"></PagerStyle>
</telerik:GridTableView> </DetailTables>
<Columns>
<telerik:GridBoundColumn DataField="PFSNO" DataType="System.Decimal" FilterControlAltText="Filter PFSNO column"
HeaderText="PFSNO" SortExpression="PFSNO" UniqueName="PFSNO">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="INSPECTIONNO" DataType="System.Decimal" FilterControlAltText="Filter INSPECTIONNO column"
HeaderText="INSPECTIONNO" ReadOnly="True" SortExpression="INSPECTIONNO" UniqueName="INSPECTIONNO">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="INPECTIONDATENTIME" FilterControlAltText="Filter INPECTIONDATENTIME column"
HeaderText="INPECTIONDATENTIME" SortExpression="INPECTIONDATENTIME" UniqueName="INPECTIONDATENTIME">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="SRS" DataType="System.Decimal" FilterControlAltText="Filter SRS column"
HeaderText="SRS" SortExpression="SRS" UniqueName="SRS">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="VIOLATIONTYPE" FilterControlAltText="Filter VIOLATIONTYPE column"
HeaderText="VIOLATIONTYPE" SortExpression="VIOLATIONTYPE" UniqueName="VIOLATIONTYPE">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="VIOLATIONDESCRIPTION" FilterControlAltText="Filter VIOLATIONDESCRIPTION column"
HeaderText="VIOLATIONDESCRIPTION" SortExpression="VIOLATIONDESCRIPTION" UniqueName="VIOLATIONDESCRIPTION">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="REMARKS" FilterControlAltText="Filter REMARKS column"
HeaderText="REMARKS" SortExpression="REMARKS" UniqueName="REMARKS">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="ITEM" FilterControlAltText="Filter ITEM column"
HeaderText="ITEM" SortExpression="ITEM" UniqueName="ITEM">
</telerik:GridBoundColumn>
<telerik:GridAttachmentColumn FileName="attachment"
FilterControlAltText="Filter column column" HeaderText="audit status-"
UniqueName="column">
</telerik:GridAttachmentColumn>
<telerik:GridTemplateColumn>
<ItemTemplate>
<telerik:RadDropDownList ID="violDrop" runat="server" DataSourceID="dd2_SqlDataSource1" DataTextField="LISTITEM" DataValueField="LISTITEM" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="true"/>
</ItemTemplate>
</telerik:GridTemplateColumn>
</Columns>
<EditFormSettings>
<EditColumn FilterControlAltText="Filter EditCommandColumn column">
</EditColumn>
</EditFormSettings>
<BatchEditingSettings EditType="Cell"></BatchEditingSettings>
<PagerStyle PageSizeControlType="RadComboBox"></PagerStyle>
</MasterTableView>
<PagerStyle PageSizeControlType="RadComboBox"></PagerStyle>
<FilterMenu EnableImageSprites="False">
</FilterMenu>
</telerik:RadGrid>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>" SelectCommand="SELECT * FROM "MEMO" WHERE ("SRS" = :SRS)">
<SelectParameters>
<asp:ControlParameter ControlID="RadGrid1" Name="SRS" PropertyName="SelectedValue"
Type="String" />
</SelectParameters>
</asp:SqlDataSource>
<asp:SqlDataSource ID="dd2_SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>" SelectCommand="SELECT "LISTITEM" FROM "DROPDOWNLIST"">
</asp:SqlDataSource>
</asp:Content>

Answer 1

Please try with the below code snippet.
Let me know if any concern.
Protected Sub DropDownList1_SelectedIndexChanged(sender As Object, e As EventArgs)
Dim item As GridDataItem = TryCast(TryCast(sender, DropDownList).NamingContainer, GridDataItem)
Dim index As Integer = item.ItemIndex
'Access current row index here
End Sub

Answer 2

First of all thanks for the reply
Unfortunately, the code snippet that you have provided didn't work for my case, it gave me an error message stating "object reference was not set to an instance of an object"
Note:I copied and pasted the code changing the name iof the index variable