Enter Data Using Databound Dynamically Created Dropdownlist

my folowwing code is generating error - selectedItem does not of string type. Basically i am unable to insert values through dropdownlist genrated dynamically.

Imports System.Data.SqlClient
Imports System.Configuration
Imports System.Data
Partial Class open_temp2
Inherits System.Web.UI.Page
Dim conn As New SqlConnection(ConfigurationManager.ConnectionStrings("ABC").ConnectionString)
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim da As New SqlDataAdapter("select partyNameID, partyName from tblParty", conn)
Dim ds As New DataSet
da.Fill(ds, "ds_tblParty")
da.SelectCommand = New SqlCommand("select quotedPositionID, quotedPosition from tblQuotedPosition", conn)
da.Fill(ds, "ds_tblQuotedPosition")
Dim I As Integer
Dim J As Integer = 1
For I = 1 To ddlNo.SelectedItem.Value
Dim MyDDL = New DropDownList
Dim MyDDL1 = New DropDownList
MyDDL.ID = "ddlParNam" & I
Session("a" & I) = MyDDL.ID
MyDDL1.ID = "ddlQuoPos" & I
Session("b" & J) = MyDDL1.ID
MyDDL.DataSource = ds.Tables("ds_tblParty").DefaultView
MyDDL.datatextfield = "partyName"
MyDDL.datavaluefield = "partyNameID"
MyDDL.DataBind()
MyDDL1.DataSource = ds.Tables("ds_tblQuotedPosition").DefaultView
MyDDL1.datatextfield = "quotedPosition"
MyDDL1.datavaluefield = "quotedPositionID"
MyDDL1.DataBind()
Panel1.Controls.Add(MyDDL)
Panel1.Controls.Add(MyDDL1)
Dim MyLiteral = New LiteralControl
MyLiteral.Text = "<BR>"
Panel1.Controls.Add(MyLiteral)
J += 1
Next
End Sub
Protected Sub btnCancel_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnCancel.Click
Response.Redirect("Default.aspx")
End Sub
Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSave.Click
Dim comm As New SqlCommand("insert into tblOBDDetails(specNoID, partyNameID, quotedPositionID) values (@specNoID, @partyNameID, @quotedPositionID)", conn)
comm.Parameters.Add("@specNoID", Data.SqlDbType.Int)
comm.Parameters("@specNoID").Value = ddlSpecNo.SelectedItem.Value
conn.Open()
Dim I As Integer
Dim J As Integer = 1
For I = 1 To ddlNo.SelectedItem.Value
comm.Parameters.Add("@partyNameID", SqlDbType.SmallInt)
comm.Parameters("@partyNameID").Value = Session("b" & I).selectedItem.value
comm.Parameters.Add("@quotedPositionID", SqlDbType.TinyInt)
comm.Parameters("@quotedPositionID").Value = Session("b" & J).selectedItem.value
comm.ExecuteNonQuery()
J += 1
Next
conn.Close()
End Sub
End Class