Dropdown List Query String Parameter

I have a dropdown list that won't populate data values from database using sql datasource. When i use the code behind, i was able to populate the data to the dropdown list. I dont know how to pass the Query String Parameter using code behind since i am new in asp.net. This is the code behind:

Imports System.Data.SqlClient
Partial Class PhotoAlbum
Inherits System.Web.UI.Page
Dim oConn As New SqlConnection("Data Source=.SQLEXPRESS;" & _
"AttachDbFilename=|DataDirectory|ASPNETDB.MDF;" & _
"Integrated Security=True;User Instance=True")
Dim oCmd As New SqlCommand()
Dim oDR As SqlDataReader
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
oConn.Open()
oCmd.CommandText = "SELECT [CategoryID], [Name] FROM Categories ORDER BY [Name]"
oCmd.Connection = oConn
oDR = oCmd.ExecuteReader()
Me.categories.DataSource = oDR
Me.categories.DataTextField = "Name"
Me.categories.DataValueField = "CategoryID"
Me.categories.DataBind()
oDR.Close()
oConn.Close()
End Sub
End Class

I will like to include the following information from sqlDatasource to the codebehind:

SelectCommand="SELECT [CategoryID], [Name] FROM [Categories] WHERE ([UserId] = @UserId) ORDER BY [Name]">
<SelectParameters>
<asp:QueryStringParameter Name="UserId" QueryStringField="ID"/>

As you can see from the code behind, i was able to add :

"SELECT [CategoryID], [Name] FROM Categories ORDER BY [Name]".

But i will like to add all of this:

SelectCommand="SELECT [CategoryID], [Name] FROM [Categories] WHERE ([UserId] = @UserId) ORDER BY [Name]">
<SelectParameters>