Error message when you use CommandBuilder: "An unhandled exception of type 'System.NullReferenceException' occurred" (310367)

SYMPTOMS

If you use the CommandBuilder object to explicitly get commands for the DataAdapter object as follows:

da.InsertCommand = cb.GetInsertCommand

and then run the following Visual Basic .NET code

cb.DataAdapter = Nothing

or the following Visual C# .NET code

cb.DataAdapter = null;

the commands that you add to the DataAdapter are deleted, and you receive the following error message:

An unhandled exception of type 'System.NullReferenceException' occurred in app_name.exe

Additional information: Object reference not set to an instance of an object.

CAUSE

CommandBuilder deletes the commands that it generates when it is disassociated from a DataAdapter. CommandBuilder and DataAdapter are linked; when they are unlinked or disassociated, the commands are nulled. This problem does not affect commands that you build from the beginning (from scratch).

MORE INFORMATION

Steps to Reproduce the Behavior

Create a new Visual Basic .NET Windows Application project. Form1 is added to the project by default.
Add a Button control to Form1.
Switch to Code view, and add the following code to the top of the Code window:
```
Imports System.Data.OleDb
Imports System.Data.SqlClient
					
```

Add the following code to the Click event of the Button:

        Dim con As New SqlConnection("server=myserver;uid=sa;pwd=mypassword;" & _
                                     "database=northwind")
        Dim da As New SqlDataAdapter("Select * From Customers", con)
        Dim cb As New SqlCommandBuilder(da)
        Dim cmdInsert As New SqlCommand( _
               "Insert Into Customer (CustomerID) Value ('AAAAA')", con)
        da.InsertCommand = cmdInsert
        da.UpdateCommand = cb.GetUpdateCommand
        da.DeleteCommand = cb.GetDeleteCommand
        Debug.WriteLine(da.InsertCommand.CommandText)
        Debug.WriteLine(da.DeleteCommand.CommandText)
        cb.DataAdapter = Nothing ' Comment out this line to avoid the error.
        cb = Nothing
        Debug.WriteLine(da.InsertCommand.CommandText)     
        Debug.WriteLine(da.DeleteCommand.CommandText)  'Error occurs here.

Modify your connection string as appropriate for your environment.
Press the F5 key to compile and to run the application.