Development | .NET Compact Framework

.NET Compact Frameworks & the ADO.NET Data Adapter
Written by Derek Mitchell  [author's bio]  [read 58290 times]
Edited by Derek

         

Page 1  Page 2  Page 3 

.NET Compact Frameworks & the ADO.NET Data Adapter

So you've been toying with jumping on the .NET cf bandwagon for months now right? Get with the program! .NET is definitely the way to go. For me it has been a tremendous learning curve to embrace and it is pretty the process is pretty much ongoing. In many ways one of the biggest challenges to .NET is coming to terms with the myriad of ways that you can architect solutions. eVB is pretty limiting and this makes things pretty easy from the perspective that there is often only one way to do it. I also got very tired of the amount of work around code required to build menus or tabs, work with XML etc., so welcome to the future - .NET Compact Framework - sure it's not the universal panacea to all mobile development but it is a huge improvement.

One of the biggest challenges in adapting to .NET is getting to grips with the new data access methodology - ADO.NET. OLE DB providers are no longer used, instead they have been usurped by .NET managed providers which are used to manage data access between the data source and your application. This may seem like an extension of the OLE dB provider approach but that is where the similarity ends. Under the hood the implementation is very different and COM has been removed from the equation. Server-side cursor support has been dropped in ADO.NET owing to the server performance and locking penalties; consideration being cast rather in favor of forward-only, read-only resultsets.

So we have established that ADO.NET is definitely the subject of whole tomes of information; before you continue too far down this path you need to have a look at Larry Roof's article called Smart Device Extensions, SQL Server CE, and Me - this will give you a great overview of the SDE environment and the basics of SQL Server CE.

Now we get to the fun part. I was putting together a tutorial on how to use combo-boxes in .NET CF and was generating some XML to use as test data. Actually the original idea here was to do some perforce testing on datasets when I lost focus and got onto the combo-box idea (more about this next week!). So my plan was that I would provide an XML file in the tutorial and then instantiate the SQL Server CE database from the XML. This is where the flexibility of the .NET data adapters and data sets really becomes apparent. So what is a dataset you ask. Think of it as your private in-memory data storage object. You can utilize one dataset populating it from different date sources, setting up relationships between the data tables it contains and then write the changes back to their respective sources. Another thing you can do is create a dataset from one source and then use a data adapter to write it to another source essentially using the data adapter as an update bridge. All this pretty easily too.

Remember to delete the devbuzztest.xml file from the Windows directory on your device after you have run the attached app - it will save you just under a 100k.

Form Load

On the form load event we create an instance of the dataset object as well as instantiating a a new SQLHelper object.

data = New DataSet()
sql = New SQLHelper()

The SQLHelper class has the usual suspects providing connectivity and SQL CE error checking, as well as some additional functionality like the TableExists function:

Function TableExists(ByVal pTableName As String) As Boolean
Dim SQL As String = "SELECT TABLE_NAME FROM " & _
"INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = '" & _
pTableName & "'"
If ceConnect() Then
Dim sqlReader As SqlCeDataReader
Dim sqlCmd As New SqlCeCommand(SQL, connCE)
Try
sqlReader = sqlCmd.ExecuteReader
Catch err As SqlCeException
ErrorDisplay(err)
Catch err As Exception
MsgBox("There was an error: " & err.ToString())
End Try
If sqlReader.Read Then
'found the name?
TableExists = True
Else
TableExists = False
End If
sqlReader = Nothing
sqlCmd = Nothing
Disconnect()
End If
End Function

Next Page 

Back to .NET Compact Framework | [Article Index]