دالة تعبئة الكومبو بوكس

'دالة تعبئة الكومبو بوكس
    Public Sub fillcombobox(ByVal cbo As ComboBox, ByVal tablename As String, ByVal col_name As String, ByVal col_value As String, ByVal whr As String)
        Try
            Dim varsql As String
            varsql = ""
            varsql = "select" + col_name + " ," + col_value + "from" + tablename + "" + whr
            Dim sda As New SqlDataAdapter(varsql, sqlconn)
            Dim ds As New DataSet()
            sda.Fill(ds)
            cbo.DataSource = ds.Tables(0)
            cbo.DisplayMember = col_name
            cbo.ValueMember = col_value
        Catch

        End Try
    End Sub

ما هو الخطا فى ذلك الكود