Developing a Data Access Layer for Sybase using ADO.NET: Essentials Continued - Getting a dataset of information from Sybase database using ADO.NET
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This mainly accepts a SQL SELECT statement as a parameter and simply returns the output of the SELECT statement in the form of a dataset in ADO.NET. Let us walk through the complete code first:
Public Function getDataSet(ByVal sqlSELECT As String, Optional
ByVal DataTableName As String = Nothing) As System.Data.DataSet
Dim da As AseDataAdapter
Try
Dim ds As New DataSet
da = New AseDataAdapter(sqlSELECT, _ConnectionString)
If DataTableName Is Nothing Then
da.Fill(ds)
Else
da.Fill(ds, DataTableName)
End If
da.Dispose()
Return ds
Catch ex As Exception
Try
da.Dispose()
Catch e As Exception
'do nothing...if still error persists
End Try
Throw New Exception(ex.Message & ". SQL Statement: "
& sqlSELECT)
End Try
End Function
The main native Sybase object I used is “AseDataAdapter” (to handle the communication between database and offline data). I declared the object as follows:
Dim da As AseDataAdapter
Let us consider the following statement:
da = New AseDataAdapter(sqlSELECT, _ConnectionString)
The statement creates an adapter which tries to execute our SELECT statement (passed in the form of parameter) based on the database connection created inline. We need not specify any connection related object. Just providing the connection string would also do the job.
Dim ds As New DataSet
If DataTableName Is Nothing Then
da.Fill(ds)
Else
da.Fill(ds, DataTableName)
End If
da.Dispose()
Return ds
I created a new dataset object which tries to hold all the data retrieved by the data adapter. The second statement (in the fragment above) checks to see if “DataTableName” is provided or not. If it is provided, it creates a data table within the data set with the user specified name or else it defaults to its own data table name. And finally the data set is returned.
I also added another method for simplifying certain scenarios (especially “data view”). The following would be the definition of “data view”:
Public Function getDataView(ByVal sqlSELECT As String) As
System.Data.DataView
Return New DataView(getDataTable(sqlSELECT))
End Function
It simply executes the SELECT statement, retrieves the data table and converts it to a new “Data View” object which finally gets returned. The “data view” is mainly used to sort or filter the information existing inside a data table. It is one of the most convenient ways to work with data returned from a database.
Next: Getting a row of information from Sybase database using ADO.NET >>
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