Login with Google in asp.net

Hi

I have requirement where user want to login from google and I need email address of that user. I have seen many example but didn't find how to get email address of particular user.

I have already tried DotNetOpenAuth it connect but how can i get email address.

Default.aspx

Log in with <img src="http://www.google.com/favicon.ico" />
            <asp:Button ID="btnLoginToGoogle" Runat="server" Text="Google" OnCommand="OpenLogin_Click"
              CommandArgument="https://www.google.com/accounts/o8/id" />
          <p /><asp:Label runat="server" ID="lblAlertMsg" />

Default.aspx.cs

using DotNetOpenAuth.OpenId;
using DotNetOpenAuth.OpenId.RelyingParty;

 protected void Page_Load(object sender, EventArgs e)
    {
        OpenIdRelyingParty rp = new OpenIdRelyingParty();
        var r = rp.GetResponse();
        if (r != null)
        {
            switch (r.Status)
            {
                case AuthenticationStatus.Authenticated:
                    var claimsResponse = r.GetExtension<ClaimsResponse>();
                   
                    lblAlertMsg.Text = r.ClaimedIdentifier;

                  
                    break;
                case AuthenticationStatus.Canceled:
                    lblAlertMsg.Text = "Cancelled.";
                    break;
                case AuthenticationStatus.Failed:
                    lblAlertMsg.Text = "Login Failed.";
                    break;
            }
        }
    }


    protected void OpenLogin_Click(object src, CommandEventArgs e)
    {
        string discoveryUri = e.CommandArgument.ToString();
        OpenIdRelyingParty openid = new OpenIdRelyingParty();
        var b = new UriBuilder(Request.Url) { Query = "" };
        var req = openid.CreateRequest(discoveryUri, b.Uri, b.Uri);
        req.RedirectToProvider();
    }