Can't Convert Oracle DataReader to SafeDataReader

elfstoneUK posted on Thursday, November 08, 2007

Ladies and Gentlemen,

your help please.

I have been using CSLA for about three weeks now and read most of the book (up to chapter 9). I'm using VB 2005 and an Oracle 10g DB in a Windows Forms design.

I'm in the process of building a prototype for the rest of the team. This is very much in the line with the Project Tracker example from the download.

So far so good. But I have hit a brick wall. I can't seem to convert from OracleDataReader to the SafeDataReader. I want to take advantage of the implicit null checking.

I have searched the forum but I can't see any resolution to this.

Can anyone tell if this can be done and how?

I have tried CType, DirectCast which compile but give an InvalidCast error at runtime!

Thanks for reading.

elfstoneUK replied on Thursday, November 08, 2007

Here is the error:

McManus replied on Thursday, November 08, 2007

Hi,

You cannot create a SafeDataReader by casting. You should call the constructor of SafeDataReader and pass in the OracleDataReader:

Dim command as OracleCommand
Dim safeReader as SafeDataReader

safeReader = New SafeDataReader(command.ExecuteReader)

Cheers,
Herman

elfstoneUK replied on Thursday, November 08, 2007

Herman,

Thanks for your reply. It worked!  Fantastic.

So we get SafeDataReader and Smartdate all from a few lines of code.

I understand what's happening but I couldn't see in until you explained it. Simple really. 

JoeFallon1 replied on Thursday, November 08, 2007

You can create a subclass of SafeDataReader in your BO project so that you can override methods to help you work with Oracle. As I recall, Oracle does not have Bit field like SQL Server does so there is a problem with GetBoolean in SafeDataReader. I use a config file setting to switch between SQL Server and Oracle. I also code my DAL to use IDataReader and return SQLDataReader or OracleDataReader based on the same setting.

Here is my version:

<Serializable()> _
Public Class MySafeDataReader
  Inherits SafeDataReader

#Region " Class Variable Declarations "
 
  Private mDBType As String = WebConfigurationManager.AppSettings("DBType")

  Public Sub New(ByVal dataReader As IDataReader)
    MyBase.New(dataReader)
  End Sub

#End Region

#Region " Properties and Methods "

  Public Overrides Function GetBoolean(ByVal i As Integer) As Boolean
    If mDBType = "SQL Server" Then
      If DataReader.IsDBNull(i) Then
        Return False
      Else
        Return DataReader.GetBoolean(i)
      End If
    ElseIf mDBType = "Oracle" Then
      If DataReader.IsDBNull(i) Then
        Return False
      Else
        If CStr(DataReader(i)) = "1" Then
          Return True
        Else
          Return False
        End If
      End If
    End If
End Function

#End Region

End Class

Joe

elfstoneUK replied on Thursday, November 08, 2007

Thanks Joe

I'm interested to learn how would you do this for the app.config?

JoeFallon1 replied on Thursday, November 08, 2007

I am not sure what you are asking here.

It is just a setting in the config file which you read on app startup.

<appSettings file="user.config">
  <add key="Authentication" value="CSLA"/>
  <add key="DBType" value="SQL Server"/>
  <!-- <add key="DBType" value="Oracle" /> -->
 <add key="ConnectionString" value="data source=joe;database=myDB;uid=myUser;password=myPwd"/>
</appSettings>

Joe

Public Shared ReadOnly Property AppSettings() As System.Collections.Specialized.NameValueCollection

Member of: System.Web.Configuration.WebConfigurationManager

elfstoneUK replied on Wednesday, November 14, 2007

Of course it is, thanks Joe