Implementing Data Transfer Objects

When you separate your business layer from data access layer in two different assembly, you come across a situation as which data transfer method will be best for me. In this example, I went through various data transfer object currently available in .NET such as XML, DataSet, DataTable, ArrayList and Custom Data Transfer Object. Each option has its pros and cons, so depending on project one should choose as what best fits the need. In the following code I have tried to use all the four possibilities.

I will be consuming the data which was returned by Data Access Layer in the form of XML, Dataset, DataTable, ArrayList and Custom (Data Transfer) Objects to populating my Business Object, which will be finally consumed by a User Interface and most likely a web page. 

In this example, I will use only one class, which will perform the CRUD operation on Customer Object by invoking method of Data Access Layer. Since I have added methods in data access layer to return Customer(s) data in form on XML, Dataset, DataTable, ArrayList and Custom (Data Transfer) Object. No matter in which form data is returned from data access layer, the business object will read that object and consume the data to make it ready for business object caller.

This Business Object will refer the assembly I previously created Vishwa.Example.Data in my earlier post Data Transfer Objects (DTO) - Data Access Layer .

Following are the steps

          Created a Class Library Project in Visual Studio 2005 using language VB.NET

 

           Project Name: Vishwa.Example.Business

          Class Name: CustomerBiz.vb

 

 

CustomerBiz.vb

' <summary>

'   Customer Business Object

' </summary>

' <remarks>

'   Design Pattern: Domain Model and Identity Field

' </remarks>

Option Explicit On

Option Strict On

Imports Vishwa.Example.Data

Imports Vishwa.Example.Data.DataAccess

 

Namespace Example.Business

 

    <Serializable()> _

    Public Class CustomerBiz

        Private _custID As Integer = 0

        Private _custName As String = String.Empty

        Private _custDOB As DateTime = DateTime.MinValue

        Private _custAddress As String = String.Empty

        Private _dateCreated As DateTime = DateTime.Now

        Private _dateModified As DateTime = DateTime.Now

 

#Region "Constructor"

        Public Sub New()

 

        End Sub

#End Region

 

#Region "Properties"

 

        Public Property CustID() As Integer

            Get

                Return _custID

            End Get

 

            Set(ByVal value As Int32)

                _custID = value

            End Set

        End Property

 

        Public Property CustName() As String

            Get

                Return _custName

            End Get

            Set(ByVal value As String)

                _custName = value

            End Set

        End Property

 

        Public Property CustDOB() As DateTime

            Get

                Return _custDOB

            End Get

            Set(ByVal value As DateTime)

                _custDOB = value

            End Set

        End Property

 

        Public Property CustAddress() As String

            Get

                Return _custAddress

            End Get

            Set(ByVal value As String)

                _custAddress = value

            End Set

        End Property

 

        Public Property DateCreated() As DateTime

            Get

                Return _dateCreated

            End Get

            Set(ByVal value As DateTime)

                _dateCreated = value

            End Set

        End Property

 

        Public Property DateModified() As DateTime

            Get

                Return _dateModified

            End Get

            Set(ByVal value As DateTime)

                _dateModified = value

            End Set

        End Property

 

        ' A Simple example of Business Logic to Get Customer Age

        ' Such logics are created in Business Logic/Object Layer    

 

        Public ReadOnly Property CustAge() As Long

            Get

                If _custDOB > DateTime.MinValue Then

                    Return DateDiff(DateInterval.Year, _custDOB, Now())

                Else

                    Return 0

                End If

            End Get

        End Property

#End Region

 

#Region "Customer Methods"

 

        Public Function AddBlankCustomer() As Integer

            Return DataProvider.InsertCustomer("unknown", DateTime.Now, "Unknown")

        End Function

 

        Public Overloads Function AddCustomer(ByVal custInfo As CustomerBiz) As Integer

            Return DataProvider.InsertCustomer(custInfo.CustName, custInfo.CustDOB, "Unknown")

        End Function

 

        Public Overloads Function AddCustomer(ByVal custName As String, ByVal custDOB As DateTime, _

                                              ByVal custAddress As String) As Integer

            Return DataProvider.InsertCustomer(custName, custDOB, custAddress)

        End Function

 

        Public Overloads Function UpdateCustomer(ByVal custInfo As CustomerBiz) As Boolean

            Return DataProvider.UpdateCustomer(custInfo.CustID, custInfo.CustName, custInfo.CustDOB, custInfo.CustAddress)

        End Function

 

        Public Overloads Function UpdateCustomer(ByVal custID As Integer, ByVal custName As String, _

             ByVal custDOB As DateTime, ByVal custAddress As String) As Boolean

            Return DataProvider.UpdateCustomer(custID, custName, custDOB, custAddress)

        End Function

 

        Public Overloads Function DeleteCustomer(ByVal custID As Integer) As Boolean

            Return DataProvider.DeleteCustomer(custID)

        End Function

 

        Public Overloads Function DeleteCustomer(ByVal custInfo As CustomerBiz) As Boolean

            Return DataProvider.DeleteCustomer(custInfo.CustID)

        End Function

 

#Region "Get Customers From Custom Data Transfer Object"

        Public Function GetCustomer(ByVal custID As Integer) As CustomerBiz

            Dim custDTORec As New CustomerDTO

            Dim custBIZRec As New CustomerBiz

            custDTORec = DataProvider.GetCustomer(custID)

            If Not custDTORec Is Nothing Then

                custBIZRec = GetCustomerRow(custDTORec)

            End If

            Return custBIZRec

        End Function

 

        Public Function GetCustomers() As List(Of CustomerBiz)

            Dim custBIZRecs As New List(Of CustomerBiz)

            Dim custDTORecs As New List(Of CustomerDTO)

            custDTORecs = DataProvider.GetCustomers

 

            For Each custDTORec As CustomerDTO In custDTORecs

                Dim custBIZRec As CustomerBiz = GetCustomerRow(custDTORec)

                custBIZRecs.Add(custBIZRec)

            Next

            Return custBIZRecs

        End Function

 

#End Region

 

#Region "Consuming Get Methods of Other Data Trasfer Objects"

 

#Region "Get Customers From DataSet Object"

        Public Function GetCustomerFromDataSet(ByVal custID As Integer) As CustomerBiz

            Dim custDataSet As New DataSet("Customer")

            Dim custBIZRec As New CustomerBiz

            custDataSet = DataProvider.GetCustomerAsDataSet(custID)

            If Not custDataSet Is Nothing AndAlso custDataSet.Tables.Count = 1 Then

                custBIZRec = GetCustomerRow(custDataSet.Tables(0).Rows(0))

            End If

            Return custBIZRec

        End Function

 

        Public Function GetCustomersFromDataSet() As List(Of CustomerBiz)

            Dim custDataSet As New DataSet("Customers")

            Dim custBIZRecs As New List(Of CustomerBiz)

            custDataSet = DataProvider.GetCustomersAsDataSet()

 

            If Not custDataSet Is Nothing AndAlso custDataSet.Tables.Count = 1 Then

                For Each row As DataRow In custDataSet.Tables(0).Rows

                    Dim custBIZRec As CustomerBiz = GetCustomerRow(row)

                    custBIZRecs.Add(custBIZRec)

                Next

            End If

            Return custBIZRecs

        End Function

 

#End Region

 

#Region "Get Customers From DataTable Object"

        Public Function GetCustomerFromDataTable(ByVal custID As Integer) As CustomerBiz

            Dim custDataTable As New DataTable("Customer")

            Dim custBIZRec As New CustomerBiz

            custDataTable = DataProvider.GetCustomerAsDataTable(custID)

 

            If Not custDataTable Is Nothing AndAlso custDataTable.Rows.Count > 0 Then

                custBIZRec = GetCustomerRow(custDataTable.Rows(0))

            End If

            Return custBIZRec

        End Function

 

        Public Function GetCustomersFromDataTable() As List(Of CustomerBiz)

            Dim custDataTable As New DataTable("Customers")

            Dim custBIZRecs As New List(Of CustomerBiz)

            custDataTable = DataProvider.GetCustomersAsDataTable()

 

            If Not custDataTable Is Nothing AndAlso custDataTable.Rows.Count > 0 Then

                For Each row As DataRow In custDataTable.Rows

                    Dim custBIZRec As CustomerBiz = GetCustomerRow(row)

                    custBIZRecs.Add(custBIZRec)

                Next

            End If

            Return custBIZRecs

        End Function

#End Region

 

#Region "Get Customers From XML"

        Public Function GetCustomerFromXML(ByVal custID As Integer) As CustomerBiz

            Dim custBIZRecs As New List(Of CustomerBiz)

            Dim custBIZRec As New CustomerBiz

 

            Dim custXMLString As String = DataProvider.GetCustomersAsXMLString()

            If custXMLString.Length > 0 Then

                custBIZRecs = ReadCustomerXML(custXMLString)

                If Not custBIZRecs.Count > 0 Then custBIZRec = custBIZRecs(0)

            End If

 

            Return custBIZRec

        End Function

 

        Public Function GetCustomersFromXML() As List(Of CustomerBiz)

            Dim custBIZRecs As New List(Of CustomerBiz)

           Dim custXMLString As String = DataProvider.GetCustomersAsXMLString()

            If custXMLString.Length > 0 Then

                custBIZRecs = ReadCustomerXML(custXMLString)

            End If

            Return custBIZRecs

        End Function

 

#End Region

 

#Region "Get Customers From ArrayList Object"

        Public Function GetCustomerFromArrayList(ByVal custID As Integer) As CustomerBiz

            Dim custBIZRec As New CustomerBiz

            Dim custArrList As New ArrayList()

            custArrList = DataProvider.GetCustomerAsArrayList(custID)

 

            If Not custArrList Is Nothing AndAlso custArrList.Count > 0 Then

                custBIZRec = GetCustomerRow(custArrList)

            End If

            Return custBIZRec

       End Function

 

        Public Function GetCustomersFromArrayList() As List(Of CustomerBiz)

            Dim custBIZRecs As New List(Of CustomerBiz)

            Dim custArrList As New ArrayList()

            custArrList = DataProvider.GetCustomersAsArrayList()

 

            If Not custArrList Is Nothing AndAlso custArrList.Count > 0 Then

                For Each row As ArrayList In custArrList

                    Dim custBIZRec As CustomerBiz = GetCustomerRow(row)

                    custBIZRecs.Add(custBIZRec)

                Next

            End If

            Return custBIZRecs

        End Function

#End Region

 

#End Region

 

#Region "Common Methods to Transfer data from DTO to Business Object"

        Private Function GetCustomerRow(ByVal row As DataRow) As CustomerBiz

            Dim custBIZRec As New CustomerBiz

            If Not IsDBNull(row.Item("Cust_ID")) Then custBIZRec.CustID = CInt(row.Item("Cust_ID"))

            If Not IsDBNull(row.Item("Cust_DOB")) Then custBIZRec.CustDOB = CDate(row.Item("Cust_DOB"))

            If Not IsDBNull(row.Item("Cust_Name")) Then custBIZRec.CustName = row.Item("Cust_Name").ToString

            If Not IsDBNull(row.Item("Cust_Address")) Then custBIZRec.CustAddress = row.Item("Cust_Address").ToString

            If Not IsDBNull(row.Item("Date_Created")) Then custBIZRec.DateCreated = CDate(row.Item("Date_Created"))

            If Not IsDBNull(row.Item("Date_Modified")) Then custBIZRec.DateModified = CDate(row.Item("Date_Modified"))

            Return custBIZRec

        End Function

 

        Private Function GetCustomerRow(ByVal custDTORec As CustomerDTO) As CustomerBiz

            Dim custBIZRec As New CustomerBiz

            custBIZRec.CustID = custDTORec.CustID

            custBIZRec.CustName = custDTORec.CustName

            custBIZRec.CustDOB = custDTORec.CustDOB

            custBIZRec.CustAddress = custDTORec.CustAddress

            custBIZRec.DateCreated = custDTORec.DateCreated

            custBIZRec.DateModified = custDTORec.DateModified

            Return custBIZRec

        End Function

 

        Private Function GetCustomerRow(ByVal custArrList As ArrayList) As CustomerBiz

            Dim custBIZRec As New CustomerBiz

            If IsNumeric(custArrList.Item(0)) Then custBIZRec.CustID = CInt(custArrList.Item(0))

            If Not custArrList.Item(1) Is Nothing Then custBIZRec.CustName = custArrList.Item(1).ToString

            If IsDate(custArrList.Item(2)) Then custBIZRec.CustDOB = CDate(custArrList.Item(2))

            If Not custArrList.Item(3) Is Nothing Then custBIZRec.CustAddress = custArrList.Item(3).ToString

            If IsDate(custArrList.Item(4)) Then custBIZRec.DateCreated = CDate(custArrList.Item(4))

            If IsDate(custArrList.Item(5)) Then custBIZRec.DateModified = CDate(custArrList.Item(5))

            Return custBIZRec

        End Function

 

        Private Function ReadCustomerXML(ByVal xmlDocString As String) As List(Of CustomerBiz)

            Dim customers As New List(Of CustomerBiz)

            Dim status As Integer = 0

            Dim statusDescription As String = String.Empty

            Dim uniEncoding As New System.Text.ASCIIEncoding()

            Dim stringBytes As Byte() = uniEncoding.GetBytes(xmlDocString)

            Dim xmlDocSteam As New System.IO.MemoryStream(stringBytes, 0, stringBytes.Length)

 

            Using xmlDocReader As System.Xml.XmlReader = System.Xml.XmlReader.Create(xmlDocSteam)

                xmlDocReader.Read()

                xmlDocReader.MoveToContent()

 

                While xmlDocReader.Read()

                    If xmlDocReader.NodeType = System.Xml.XmlNodeType.Element And xmlDocReader.Name = "Customer" Then

                        Dim custRec As New CustomerBiz

                        While (xmlDocReader.Read() And xmlDocReader.Name <> "Customer")

                            If xmlDocReader.Name.Length > 0 Then

                                If xmlDocReader.Name = "Cust_ID" Then custRec.CustID = xmlDocReader.ReadElementContentAsInt("Cust_ID", "")

                                If xmlDocReader.Name = "Cust_Name" Then custRec.CustName = xmlDocReader.ReadElementContentAsString("Cust_Name", "")

                                If xmlDocReader.Name = "Cust_DOB" Then custRec.CustDOB = xmlDocReader.ReadElementContentAsDateTime("Cust_DOB", "")

                                If xmlDocReader.Name = "Cust_Address" Then custRec.CustAddress = xmlDocReader.ReadElementContentAsString("Cust_Address", "")

                                If xmlDocReader.Name = "Date_Created" Then custRec.DateCreated = xmlDocReader.ReadElementContentAsDateTime("Date_Created", "")

                                If xmlDocReader.Name = "Date_Modified" Then custRec.DateModified = xmlDocReader.ReadElementContentAsDateTime("Date_Modified", "")

                            End If

                        End While

                        customers.Add(custRec)

                    End If

                End While

            End Using

            xmlDocSteam.Close()

            Return customers

        End Function

 

#End Region

 

#End Region

 

    End Class

End Namespace

Compiled Assembly Name: Vishwa.Example.Business.dll

Now you can use the reference of the above assembly for customer object in your ASP.NET Web Page and test the functionality.