DropDownList qui filtre autre DropDownList

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

If Not IsPostBack Then
Dim da As New SqlDataAdapter("SELECT Id_Client, Nom_Client, Prenom_Client FROM Client ", conn)
da.Fill(ds, "Client")
ddlNom.DataSource = ds.Tables("Client")
ddlNom.DataTextField = "Nom_Client"
ddlNom.DataValueField = "Nom_Client"
ddlNom.DataBind()
End If

Dim de As New SqlDataAdapter("SELECT * FROM Client Where Nom_Client =" & ddlNom.SelectedItem.Value, conn)
de.Fill(ds, "Client")
ddlPrenom.DataSource = ds.Tables("Client")
ddlPrenom.DataTextField = "Prenom_Client"
ddlPrenom.DataValueField = "IdTitre_Client"
ddlPrenom.DataBind()
End Sub

Line 23: 
Line 24:         Dim de As New SqlDataAdapter("SELECT * FROM Client Where nom_Client =" & ddlNom.SelectedItem.Value, conn)
Line 25:         de.Fill(ds, "Client")
Line 26: 
Line 27:         ddlPrenom.DataSource = ds.Tables("Client")