SelectedIndex Value from Bound Control

[karth23]

I have 3 Tables
Data Structure Below
Table1:
ADDRESS_ID INT ( Seed ) Primary Key
ST_ID INT Foriegn Key
CNT_ID INT Foriegn Key
First_NM NVARCHAR(50)

Table 2:
ST_ID INT Primary Key
ST_CD INT
ST_NM NVARCHAR(50)

Table3:
CNT_ID INT Primary Key
CNT_NM VARCHAR(50)

I have created 3 DataAdapter one Dataset
Default.aspx file has a datagrid, textbox controls and Update and Add Buttons.
I have one DropDownList Control (Bind Control) for display State abrivation.

i..e ST_CD from Table2
If the User select and a row from the Datagrid the details will display on appropriate text boxes
and dropdownList box.

My problem is I couldn't get the ID value i.e ST_ID from the Selected Dropdownlist when the user
click the Add button. How could I get the ID Value from the DropdownListbox

My dropdownlistbox name is ddlState
I am trying to get the ST_ID using the following code

i.e dr("ST_D&quot = ddlState.SelectedItem.Value

The above code is working fine when I user click Update button

The following code working fine for updation.

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

If Not Page.IsPostBack Then

SqlCnn.Open()

'Table1: - Address_Lst
DAAddressUSA.FillSchema(DsAddressBook1, SchemaType.Mapped, "Address_Lst&quot
DAAddressUSA.Fill(DsAddressBook1, "Address_Lst&quot

'Table3: - Country_Lst
DACountry.FillSchema(DsAddressBook1, SchemaType.Mapped, "Country_Lst&quot
DACountry.Fill(DsAddressBook1, "Country_Lst&quot

'Table2: - State_USA
DAState.FillSchema(DsAddressBook1, SchemaType.Mapped, "State_USA&quot
DAState.Fill(DsAddressBook1, "State_USA&quot

Session.Add("dsAddressUSA", DsAddressBook1)
dgUSA.DataBind()

End If

End Sub

Private Sub UpdateRow()
DsAddressBook1 = Session("dsAddressUSA&quot

Dim dt As DataTable = DsAddressBook1.Tables("Address_Lst&quot
Dim dr As DataRow()

'Get the seleced row using Address_Id
dr = dt.Select("Address_ID ='" + lblID.Text + "'&quot

dr(0)("FIRST_NM&quot = txtFirstName.Text.Trim
dr(0)("ST_ID&quot = ddlState.SelectedItem.Value

DAAddressUSA.Update(dr)

Session.Add("dsAddressUSA", DsAddressBook1)
UpdateRecords()
End Sub

Private Sub UpdateRecords()
DsAddressBook1 = Session("dsAddressUSA&quot
'dbUSA - DataGrid
dgUSA.DataBind()
End Sub

The Following Code not working

Private Sub InsertRow()

DsAddressBook1 = Session("dsAddressUSA&quot
Dim dt As DataTable = DsAddressBook1.Tables("Address_Lst&quot
Dim dr As DataRow = DsAddressBook1.ADDRESS_LST.NewRow

dr("FIRST_NM&quot = txtFirstName.Text.Trim
dr("ST_ID&quot = ddlState.SelectedItem.Value

DsAddressBook1.ADDRESS_LST.ADDRESS_IDColumn.AutoIncrementSeed = True
DsAddressBook1.ADDRESS_LST.AddADDRESS_LSTRow(dr)
DAAddressUSA.UpdateCommand = Me.SqlInsertCommand1()
DAAddressUSA.Update(DsAddressBook1)
Session.Add("dsAddressUSA", DsAddressBook1)
UpdateRecords()
End Sub

The above Insert return the following error
"Object reference not set to an instance of an object. "
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Could any one help me to resolve this error.

Karthik Bala