(عنوان مخالف)اريد حل هذه المشكلة

Public Class Form1

 Dim aa As String = SheetT.Text
    Dim AD As New SqlDataAdapter("SELECT * FROM IntD where (Sheet='" & aa & "')", conn)
    Dim CMDB As New SqlCommandBuilder
    Dim DBS As New Data.DataSet
 

An error occurred creating the form. See Exception.InnerException for details.  The error is: Object reference not set to an instance of an object.