-----------------------------------------------------------
New Message on BDOTNET
-----------------------------------------------------------
From: AnujAhuja
Message 5 in Discussion
Hi Ramu,
While taking a simple example I'll try to explain how we can use disconnect Connection
to connect get data form the database in object oriented world.
Take Example of Order Class, Following Diagram shows relationship
Following will explain Source code will explain rest of things
' Create new Access Database Order.mdb
' Create new Table Called Order with following fields
' OrderNumber : Number
' Orderdate : Date/Time
' ItemName : Text
' And then either modify Connection String according to path of access
' database file or place it at c:
Public Class DataManager
' Database handing class
' Can have singleton implementation
' This class will have ADO.net connection in disconnected mode
' When ever data is requested then only it opens the connection, get data, close
connection and return data to the client
Private strConnectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data
Source=C:\Order.mdb"
Private oConnection As Data.OleDb.OleDbConnection
Private oCommand As Data.OleDb.OleDbCommand
Public Sub New()
Try
oConnection = New Data.OleDb.OleDbConnection(strConnectionString)
oCommand = New Data.OleDb.OleDbCommand()
oCommand.Connection = oConnection
oCommand.CommandType = CommandType.Text
Catch ex As Exception
MsgBox("Cant able to create connection object!")
End Try
End Sub
Public Function GetData(ByVal Sql As String) As DataTable
oCommand.CommandText = Sql
Try
Dim oAdapter As New Data.OleDb.OleDbDataAdapter(oCommand)
Dim oDataTable As New DataTable()
' Hear connection will be opened, used and closed by the adapter
oAdapter.Fill(oDataTable)
Return oDataTable
Catch ex As Exception
MsgBox("Cant able to execute SQL!")
Return Nothing
End Try
End Function
Public Function SaveData(ByVal Sql As String) As Boolean
oCommand.CommandText = Sql
Try
oConnection.Open()
oCommand.ExecuteNonQuery()
oConnection.Close()
Return True
Catch ex As Exception
MsgBox("Cant able to execute SQL!")
Return False
End Try
End Function
End Class
Public Class Order
' Simple Order Class
Public OrderNumber As Integer
Public OrderDate As Date
Public ItemName As String
Private IsNew As Boolean
Dim oDataManager As New DataManager()
Public Sub New(ByVal OrderNumber As Integer)
' If requested Order Number Exits then it will load details from Order Table
' Otherwise it will set IsNew Flag to True so that Insert statement can be used for
' saving data in Order Table for the first time
Dim SQL As String = "Select * from [Order] where OrderNumber = " &
OrderNumber.ToString
Dim oDatatable As New DataTable()
oDatatable = oDataManager.GetData(SQL)
Me.OrderNumber = OrderNumber
If oDatatable.Rows.Count <> 0 Then
OrderDate = CDate(oDatatable.Rows(0)("OrderDate").ToString)
ItemName = oDatatable.Rows(0)("ItemName").ToString
IsNew = False
Else
IsNew = True
End If
End Sub
Public Sub Save()
If IsNew Then
oDataManager.SaveData("INSERT INTO [Order] Values(" & OrderNumber & "," &
OrderDate.ToShortDateString & ", '" & ItemName & "' )")
IsNew = False
Else
oDataManager.SaveData(String.Format("UPDATE [Order] SET Orderdate = {0}, ItemName =
'{1}' WHERE OrderNumber={2}", OrderDate.ToShortDateString, ItemName, OrderNumber))
End If
End Sub
End Class
Public Class MainClass
Public Shared Sub main()
' Creating Order Object of Existing Order details in Order Table i.e. Order Number 1
Console.WriteLine(" Creating Order Object of Existing Order Number 1")
Dim oOrder As New Order(1)
Console.WriteLine("Order Number :" & oOrder.OrderNumber)
Console.WriteLine("Order Date :" & oOrder.OrderDate)
Console.WriteLine("Item Name :" & oOrder.ItemName)
' Creating Order object who's detail is not present in Order Table and Saving it
Console.WriteLine(" Creating Order object who's details are not present and Saving
it")
Dim anotherOrder As New Order(2)
anotherOrder.ItemName = "IBM"
anotherOrder.OrderDate = Now
Console.WriteLine("Order Number :" & anotherOrder.OrderNumber)
Console.WriteLine("Order Date :" & anotherOrder.OrderDate)
Console.WriteLine("Item Name :" & anotherOrder.ItemName)
anotherOrder.Save()
Console.ReadLine()
End Sub
End Class
I hope this will help
- Anuj
(Sky is the Limit)
View Attachment(s):
http://groups.msn.com/bdotnet/_notifications.msnw?type=msg&mview=1&parent=1&item=18874
-----------------------------------------------------------
To stop getting this e-mail, or change how often it arrives, go to your E-mail
Settings.
http://groups.msn.com/bdotnet/_emailsettings.msnw
Need help? If you've forgotten your password, please go to Passport Member Services.
http://groups.msn.com/_passportredir.msnw?ppmprop=help
For other questions or feedback, go to our Contact Us page.
http://groups.msn.com/contact
If you do not want to receive future e-mail from this MSN group, or if you received
this message by mistake, please click the "Remove" link below. On the pre-addressed
e-mail message that opens, simply click "Send". Your e-mail address will be deleted
from this group's mailing list.
mailto:[EMAIL PROTECTED]
