Question

Aim to Achieve :
I want to have 3 different dataTables from 3 different SQL queries from 3 different places into 1 single DataSet which I will have to return form my function.

I have :

Private Function getDataSet()
    Dim ad1,ad2,ad3 As Object
    ad1 = New Data.OleDb.OleDbDataAdapter(query1, conStr1)
    ad2 = New Data.SqlClient.SqlDataAdapter(query2, conStr2)
    ad3 = New Data.SqlClient.SqlDataAdapter(query3, conStr3)
    Dim dataSet As New Data.DataSet

    // I want to fill dataSet with the 3 adapters !
    // ad1.Fill(dataSet) : ad2.Fill(dataSet) : ad3.Fill(dataSet)
    // Will this work ?

    ad1.Dispose() : ad2.Dispose() : ad3.Dispose()  // What does Dispose() method do ?
    Return dataSet
End Function

Dim ds = getDataSet()
data1 = ds.Tables(0)
data2 = ds.Tables(1)
data3 = ds.Tables(2)

Please Help..

• I want to use the best possible implementation of above task.

Answer 1

I would not fill the DataSet but the DataTables of the DataSet with each DataAdapter:

Private Function getDataSet() As DataSet
    Dim ds As New Data.DataSet
    ds.Tables.Add(New DataTable("Table1"))
    ds.Tables.Add(New DataTable("Table2"))
    ds.Tables.Add(New DataTable("Table3"))

    Using con As New OleDb.OleDbConnection("conStr1")
        Using ad As New Data.OleDb.OleDbDataAdapter("query1", con)
            con.Open()
            ad.Fill(ds.Tables("Table1"))
        End Using
    End Using
    Using con As New OleDb.OleDbConnection("conStr2")
        Using ad As New Data.OleDb.OleDbDataAdapter("query2", con)
            con.Open()
            ad.Fill(ds.Tables("Table2"))
        End Using
    End Using
    Using con As New OleDb.OleDbConnection("conStr3")
        Using ad As New Data.OleDb.OleDbDataAdapter("query3", con)
            con.Open()
            ad.Fill(ds.Tables("Table3"))
        End Using
    End Using

    Return ds
End Function

Any number of DataAdapter-objects can be used with a DataSet. Each
DataAdapter can be used to fill one or more DataTable objects and
resolve updates back to the relevant data source. DataRelation and
Constraint objects can be added to the DataSet locally, which enables
you to relate data from dissimilar data sources. For example, a
DataSet can contain data from a Microsoft SQL Server database, an IBM
DB2 database exposed through OLE DB, and a data source that streams
XML. One or more DataAdapter objects can handle communication to each
data source.

More…

” // What does Dispose() method do ?”

http://msdn.microsoft.com/en-us/library/system.idisposable.dispose.aspx

Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

I would prefer the using-statement(see code-sample above) because it’s simplier and also closes connection etc.