Unable to get current url string in hyperlink's NavigateUrl

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C#

C#4.0

ASP.NET4

I have following code in MasterPage.aspx page to logout the user:

<asp:HyperLink ID="HyperLink1" runat="server" Font-Bold="True" ForeColor="#333333"
                                            Font-Underline="False" NavigateUrl='<%#"~/DeleteCookie.aspx?currenturl="+thisurl()%>' >|Logout</asp:HyperLink>

I want to pass current url to DeleteCookie.aspx page as QueryString so that the current page can be redirected(Refresh).
I am using following code in file of MasterPage.aspx.cs:

protected string thisurl()
    {
        return HttpUtility.UrlEncode(Request.Url.AbsoluteUri);
    }

But its not working because I am unable to click on hyperlink.
Please help in finding the solution.