How to logout from FaceBook website using Graph API in ASPNet

In this article I will explain how to logout of FaceBook Website in ASP.Net using the Free ASPSnippets FaceBook API.

Note: You can download the latest ASPSnippets.FaceBookAPI.dll clicking the download link below.

Download DLL file

More FaceBook Articles

Upload ( Post ) Photo ( Image ) to Facebook Wall using Graph API in ASP.Net

Facebook - Get Full size Profile Picture of user in ASP.Net using C# and VB.Net

ASP.Net Get Facebook User details like Gender, Email, Address Location and Birth Date

Import Facebook Album Photos and display as Image Gallery in ASP.Net

Post Publish and Share content on user’s Facebook Wall using Graph API in ASP.Net

Fetch and import Facebook Friends and Contacts with profile pictures in ASP.Net

Create FaceBook Application and get App Id

You will need to create an application and get an API Key and API Secret. You can refer my article

Create FaceBook App and Facebook Application Id ( AppId ) and Secret Key

HTML Markup

In the below HTML Markup I have placed an ASP.Net Button btnLogin to authenticate the user through FaceBook and get its profile details like FaceBook UserId, Username, Name, Email, Profile picture and a button to logout from FaceBook website.

<asp:Button ID="btnLogin" runat="server" Text="Login with FaceBook" OnClick="Login" />

<asp:Panel ID="pnlFaceBookUser" runat="server" Visible="false">

<hr />

<table>

<tr>

<asp:Image ID="ProfileImage" runat="server" Width="50" Height="50" />

</td>

</tr>

<tr>

<td>

ID:<asp:Label ID="lblId" runat="server" Text=""></asp:Label>

</td>

</tr>

<tr>

<td>

UserName:<asp:Label ID="lblUserName" runat="server" Text=""></asp:Label>

</td>

</tr>

<tr>

<td>

Name:<asp:Label ID="lblName" runat="server" Text=""></asp:Label>

</td>

</tr>

<tr>

<td>

Email:<asp:Label ID="lblEmail" runat="server" Text=""></asp:Label>

</td>

</tr>

<tr>

<asp:Button ID="btnLogout" runat="server" Text="Logout" OnClick="Logout" />

</td>

</tr>

</table>

</asp:Panel>

Namespaces

You will need to import the following Namespaces

using ASPSnippets.FaceBookAPI;

using System.Web.Script.Serialization;

VB.Net

Imports ASPSnippets.FaceBookAPI

Imports System.Web.Script.Serialization

Data Class

You will need to create the following class which will be used to hold the User Profile details returned from FaceBook after authentication.

public class FaceBookUser

{

public string Id { get; set; }

public string Name { get; set; }

public string UserName { get; set; }

public string PictureUrl { get; set; }

public string Email { get; set; }

}

VB.Net

Public Class FaceBookUser

Public Property Id() As String

Get

Return m_Id

End Get

Set(value As String)

m_Id = value

End Set

End Property

Private m_Id As String

Public Property Name() As String

Get

Return m_Name

End Get

Set(value As String)

m_Name = value

End Set

End Property

Private m_Name As String

Public Property UserName() As String

Get

Return m_UserName

End Get

Set(value As String)

m_UserName = value

End Set

End Property

Private m_UserName As String

Public Property PictureUrl() As String

Get

Return m_PictureUrl

End Get

Set(value As String)

m_PictureUrl = value

End Set

End Property

Private m_PictureUrl As String

Public Property Email() As String

Get

Return m_Email

End Get

Set(value As String)

m_Email = value

End Set

End Property

Private m_Email As String

End Class

Authenticate user using FaceBook account

On the click of the ASP.Net Button btnLogin we redirect the User to FaceBook and ask him to authenticate himself as wells as provide permission to access to his FaceBook profile details like FaceBook UserId, Username, Name, Email and Profile picture

protected void Login(object sender, EventArgs e)

{

FaceBookConnect.Authorize("user_photos,email", Request.Url.AbsoluteUri.Split('?')[0]);

}

VB.Net

Protected Sub Login(sender As Object, e As EventArgs)

FaceBookConnect.Authorize("user_photos,email", Request.Url.AbsoluteUri.Split("?"c)(0))

End Sub

Fetch the user’s FaceBook Profile details

The below code checks for access code (access token) in Query string and then based on the access code it fetches the user’s FaceBook profile details like FaceBook UserId, Username, Name, Email and Profile picture.

Also in the Page Load event I have handled the following two cases

1. Access Denied: - This allows us to determine whether user has denied access to the FaceBook App.

2. Logout: - This allows us to determine whether user has logged out from the FaceBook Website.

protected void Page_Load(object sender, EventArgs e)

{

FaceBookConnect.API_Key = "<Your API Key>";

FaceBookConnect.API_Secret = "<Your API Secret>";

if (!IsPostBack)

{

if (Request.QueryString["logout"] == "true")

{

ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('User has logged out from Facebook')", true);

return;

}

if (Request.QueryString["error"] == "access_denied")

{

ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('User has denied access.')", true);

return;

}

string code = Request.QueryString["code"];

if (!string.IsNullOrEmpty(code))

{

string data = FaceBookConnect.Fetch(code, "me?fields=id,name,email");

FaceBookUser faceBookUser = new JavaScriptSerializer().Deserialize<FaceBookUser>(data);

faceBookUser.PictureUrl = string.Format("https://graph.facebook.com/{0}/picture", faceBookUser.Id);

pnlFaceBookUser.Visible = true;

lblId.Text = faceBookUser.Id;

lblUserName.Text = faceBookUser.UserName;

lblName.Text = faceBookUser.Name;

lblEmail.Text = faceBookUser.Email;

ProfileImage.ImageUrl = faceBookUser.PictureUrl;

btnLogin.Enabled = false;

}

VB.Net

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load

FaceBookConnect.API_Key = "<Your API Key>"

FaceBookConnect.API_Secret = "<Your API Secret>"

If Not IsPostBack Then

If Request.QueryString("logout") = "true" Then

ClientScript.RegisterStartupScript(Me.[GetType](), "alert", "alert('User has logged out from Facebook')", True)

Return

End If

If Request.QueryString("error") = "access_denied" Then

ClientScript.RegisterStartupScript(Me.[GetType](), "alert", "alert('User has denied access.')", True)

Return

End If

Dim code As String = Request.QueryString("code")

If Not String.IsNullOrEmpty(code) Then

Dim data As String = FaceBookConnect.Fetch(code, "me?fields=id,name,email")

Dim faceBookUser As FaceBookUser = New JavaScriptSerializer().Deserialize(Of FaceBookUser)(data)

faceBookUser.PictureUrl = String.Format("https://graph.facebook.com/{0}/picture", faceBookUser.Id)

pnlFaceBookUser.Visible = True

lblId.Text = faceBookUser.Id

lblUserName.Text = faceBookUser.UserName

lblName.Text = faceBookUser.Name

lblEmail.Text = faceBookUser.Email

ProfileImage.ImageUrl = faceBookUser.PictureUrl

btnLogin.Enabled = False

End If

End Sub

Logout from FaceBook using Graph API

Below is the event handler which is raised when the Logout button is clicked, it simply makes call to the ASPSnippets FaceBook API Logout method and passes the FaceBook Graph API Access Code as parameter.

protected void Logout(object sender, EventArgs e)

{

FaceBookConnect.Logout(Request.QueryString["code"]);

}

VB.Net

Protected Sub Logout(sender As Object, e As EventArgs)

FaceBookConnect.Logout(Request.QueryString("code"))

End Sub

1. Press the Login button in order to login through FaceBook