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ADOCE is a fantastic tool allowing eVB
programmers easy access to the native data store, Pocket
Access and SQL Server 2000 CE Edition databases. It has
a subset of the desktop ADO objects, properties and methods
and makes using databases a snap. Unfortunately, it has
some flaws. One of the most disturbing problems is that
if you're using ADOCE to modify data in a database, including
inserts, deletes and updates, the modifications are not
fully committed to the database volume until your application
exits. This holds true for ADOCE 3.0 and 3.1 on the Pocket
PC and HPC.
To see what I mean, create a simple
project and use the Recordset object to insert data into
a table. Create a project with a single form and add 3 Command
Buttons and a ListBox to it. Something like Figure 1.
Then add the following code to the form's
code page:
Private rs As ADOCE.Recordset
Private cn As ADOCE.Connection
Private Sub Command1_Click()
On Error Resume Next
' Open the connection
cn.ConnectionString = ""
cn.Open
' Create the DB
' not graceful, but if the DB exists,
' the On Error will handle this
cn.Execute "CREATE DATABASE '\ADOCETest.cdb'"
' change the connection to our DB
cn.Close
cn.ConnectionString = "\ADOCETest.cdb"
cn.Open
' create the table
cn.Execute "CREATE TABLE " _
& "TestTable(Name varchar(30))"
cn.Close
End Sub
Private Sub Command2_Click()
cn.ConnectionString = "\ADOCETest.cdb"
cn.Open
' Insert data
cn.Execute "INSERT INTO TestTable " _
& "VALUES('Fred')"
cn.Execute "INSERT INTO TestTable " _
& "VALUES('Wilma')"
cn.Execute "INSERT INTO TestTable " _
& "VALUES('Barney')"
cn.Execute "INSERT INTO TestTable " _
& "VALUES('Betty')"
cn.Close
End Sub
Private Sub Command3_Click()
cn.ConnectionString = "\ADOCETest.cdb"
cn.Open
' retrieve the data
Set rs = cn.Execute("SELECT * FROM TestTable")
' clear the list
List1.Clear
' display the data
Do While Not rs.EOF
List1.AddItem rs.Fields("Name").Value
rs.MoveNext
Loop
cn.Close
End Sub
Private Sub Form_Load()
Set cn = CreateObject("ADOCE.Connection.3.0")
End Sub
Private Sub Form_OKClick()
App.End
End Sub
Now let's expose the "soft underbelly"
of ADOCE. Run the application and tap the first button to
create the database and table, then exit the application.
It is important that you exit the application at this point
to ensure the table is created.
Next, re-start the application and tap
the second two buttons in succession to populate our table
and then retrieve and show the data. You should get an output
like Figure 2. We've inserted 4 records into our
table, or have we?
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