Variables de sesión en WebServices

En este artículo veremos la forma de acceder desde distintos tipos de cliente (Windows Form y Web Form) a un WebService que posee variables de sesión sin que se pierda el contenido entre las distintas llamadas al mismo.

Primero desarrollaremos el WebService, modificando el atributo WebMethod con la propiedad EnableSession, para que el mismo permita utilizar variables de sesión.

Imports System.Web.Services

<System.Web.Services.WebService(Namespace:="http:"//tempuri.org/SessionCountWS/SessionCount")> _
Public Class SessionCount
    Inherits System.Web.Services.WebService

#Region " Web Services Designer Generated Code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Web Services Designer.
        InitializeComponent()

        'Add your own initialization code after the InitializeComponent() call

    End Sub

    'Required by the Web Services Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Web Services Designer
    'It can be modified using the Web Services Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        components = New System.ComponentModel.Container
    End Sub

    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        'CODEGEN: This procedure is required by the Web Services Designer
        'Do not modify it using the code editor.
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

#End Region

    <WebMethod(EnableSession:=True)> _
    Public Function Count() As Integer
        If Session.Item("SessionCount") Is Nothing Then
            Session.Item("SessionCount") = 1
        Else
            Session.Item("SessionCount") = CInt(Session.Item("SessionCount")) + 1
        End If
        Return CInt(Session.Item("SessionCount"))
    End Function
End Class

Ahora veremos como hacer desde el código del cliente para que al llamar al WebService mantenga la sesión.

 

Cliente Windows Form:

Primero debemos declarar un objeto del tipo System.Net.CookieContainer para luego asignárselo al WebService.

Private Cookies As System.Net.CookieContainer

Ahora declaramos el WebService, le asociamos las cookies al mismo y lo llamamos.

Private wsSessionCount As New SessionCountWS.SessionCount
wsSessionCount.CookieContainer = Cookies
MsgBox(wsSessionCount.Count.ToString)

Con estos pasos, logramos mantener la sesión con que se llama al WebService en el cliente.

Veamos un ejemplo completo del mismo:

Public Class SessionCount
    Inherits System.Windows.Forms.Form

    Private Cookies As System.Net.CookieContainer
    Private wsSessionCount As New SessionCountWS.SessionCount

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call
        If Cookies Is Nothing Then
            Cookies = New System.Net.CookieContainer
        End If
        wsSessionCount.CookieContainer = Cookies
    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    Friend WithEvents TextBoxSessionCount As System.Windows.Forms.TextBox
    Friend WithEvents ButtonSessionCount As System.Windows.Forms.Button
    Friend WithEvents ButtonSessionCountGet As System.Windows.Forms.Button
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.TextBoxSessionCount = New System.Windows.Forms.TextBox
        Me.ButtonSessionCount = New System.Windows.Forms.Button
        Me.ButtonSessionCountGet = New System.Windows.Forms.Button
        Me.SuspendLayout()
        '
        'TextBoxSessionCount
        '
        Me.TextBoxSessionCount.Location = New System.Drawing.Point(102, 65)
        Me.TextBoxSessionCount.Name = "TextBoxSessionCount"
        Me.TextBoxSessionCount.ReadOnly = True
        Me.TextBoxSessionCount.Size = New System.Drawing.Size(88, 20)
        Me.TextBoxSessionCount.TabIndex = 0
        Me.TextBoxSessionCount.Text = "0"
        Me.TextBoxSessionCount.TextAlign = System.Windows.Forms.HorizontalAlignment.Center
        '
        'ButtonSessionCount
        '
        Me.ButtonSessionCount.Location = New System.Drawing.Point(102, 121)
        Me.ButtonSessionCount.Name = "ButtonSessionCount"
        Me.ButtonSessionCount.Size = New System.Drawing.Size(88, 23)
        Me.ButtonSessionCount.TabIndex = 1
        Me.ButtonSessionCount.Text = "Count"
        '
        'ButtonSessionCountGet
        '
        Me.ButtonSessionCountGet.Location = New System.Drawing.Point(104, 179)
        Me.ButtonSessionCountGet.Name = "ButtonSessionCountGet"
        Me.ButtonSessionCountGet.Size = New System.Drawing.Size(88, 23)
        Me.ButtonSessionCountGet.TabIndex = 2
        Me.ButtonSessionCountGet.Text = "Get Count"
        '
        'SessionCount
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(292, 266)
        Me.Controls.Add(Me.ButtonSessionCountGet)
        Me.Controls.Add(Me.ButtonSessionCount)
        Me.Controls.Add(Me.TextBoxSessionCount)
        Me.Name = "SessionCount"
        Me.Text = "SessionCount"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Private Sub ButtonSessionCount_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonSessionCount.Click
        TextBoxSessionCount.Text = wsSessionCount.Count.ToString
    End Sub
End Class

 

Cliente Web Form:

En este caso, si bien se maneja de la misma forma que un cliente Windows Form, hay que almacenar las cookies en una variable de sesión, para no perder las mismas entre llamados.

Session("Cookies") = Cookies

Ver el ejemplo siguiente, el manejo recién comentado se encuentra en el método ButtonSessionCount_Click(…):

Public Class SessionCount
    Inherits System.Web.UI.Page

#Region " Web Form Designer Generated Code "

    'This call is required by the Web Form Designer.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()

    End Sub
    Protected WithEvents ButtonSessionCount As System.Web.UI.WebControls.Button
    Protected WithEvents TextBoxSessionCount As System.Web.UI.WebControls.TextBox

    'NOTE: The following placeholder declaration is required by the Web Form Designer.
    'Do not delete or move it.
    Private designerPlaceholderDeclaration As System.Object

    Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
        'CODEGEN: This method call is required by the Web Form Designer
        'Do not modify it using the code editor.
        InitializeComponent()
    End Sub

#End Region

    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'Put user code to initialize the page here

    End Sub

    Private Sub ButtonSessionCount_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonSessionCount.Click
        Dim Cookies As System.Net.CookieContainer
        If Session("Cookies") Is Nothing Then
            Cookies = New System.Net.CookieContainer
        Else
            Cookies = Session("Cookies")
        End If
        Dim wsSessionCount As New SessionCountWS.SessionCount
        wsSessionCount.CookieContainer = Cookies
        TextBoxSessionCount.Text = wsSessionCount.Count.ToString
        Session("Cookies") = Cookies
    End Sub

End Class

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Espacios de nombres usados en el código de este artículo:

System.Web.Services