Developing a Data Access Layer for Sybase Using ADO.NET: Essentials - The Constructor in the Data Access Layer
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Our DAL needs to have a “key” (the key of the connection string in web.config file) passed so that it gets connected accordingly. The following could be the code for the constructor:
Public Sub New(ByVal ConnStrConfigKey As String)
Try
Dim ConnectionString As String =
System.Configuration.ConfigurationSettings.AppSettings.Get
(ConnStrConfigKey)
_ConnectionString = ConnectionString
If Len(Trim(_ConnectionString & "")) = 0 Then Throw
New Exception("Connection String not configured")
Catch ex As Exception
Throw New Exception(ex.Message & ". Invalid Database
Configuration ")
End Try
End Sub
Before defining the above constructor, I declared a simple class level variable to hold the connection string as follows:
Private _ConnectionString As String
From now on we can use above variable to work with the connection string. The following line retrieves the connecting string from web.config file:
Dim ConnectionString As String =
System.Configuration.ConfigurationSettings.AppSettings.Get
(ConnStrConfigKey)
We check for the validation of connection string as follows:
If Len(Trim(_ConnectionString & "")) = 0 Then Throw
New Exception("Connection String not configured")
And that completes our initial steps for working with the connection string. Apart from the above constructor, I also managed to import the Sybase namespace at the top of my class as follows:
Imports Sybase.Data.AseClient
That is the only external assembly I added as reference to the project. It is the most essential assembly for connecting to Sybase natively. The other imports are as follows:
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports Sybase.Data.AseClient
Imports System.Xml.Serialization
Imports System.IO
Imports System.Text
Next: Getting a table (or data table) of information from Sybase database using ADO.NET >>
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