Value Cannot be null in Ado.Net connectivity

<input type="button" id="fblogin" value="Login to Facebook" disabled="disabled" style="display:none"/>
        <fb:login-button v="2" length="long" onlogin="window.location = 'Default.aspx'">Login to Facebook</fb:login-button>

<div id="fb-root"></div>
<script>
    window.fbAsyncInit = function () {
        FB.init({
            appId: '<%: Facebook.FacebookApplication.Current.AppId %>',
            cookie: true,
            xfbml: true,
            oauth: true
        });

        function facebooklogin() {
            FB.login(function (response) {
                if (response.authResponse) {
                    // user authorized
                    // make sure to set the top.location instead of using window.location.reload()
                    top.location = '<%= this.ResolveCanvasPageUrl("~/") %>';
                } else {
                    // user cancelled
                }
            }, { scope: '<%: string.Join(",", ExtendedPermissions) %>' });
        };

        $(function () {
            // make the button is only enabled after the facebook js sdk has been loaded.
            $('#fblogin').attr('disabled', false).click(facebooklogin);
        });
    };
    (function () {
        var e = document.createElement('script'); e.async = true;
        e.src = document.location.protocol + '//connect.facebook.net/en_US/all.js';
        document.getElementById('fb-root').appendChild(e);
    } ());
</script>

HttpGet httpget=null;
String mContent=null;
HttpClient Client=null;

Client = new DefaultHttpClient();
Client.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 500);
httpget = new HttpGet(url);
ResponseHandler<String> responseHandler = new BasicResponseHandler();
try {
    mContent = Client.execute(httpget, responseHandler);
    return true;
} catch (IOException e) {
    e.printStackTrace();
}
return false;

    HttpParams params = new BasicHttpParams();
    HttpConnectionParams.setConnectionTimeout(params, 500);

    Client = new DefaultHttpClient(params);

public static boolean isConnected(Context context){
    ConnectivityManager
            cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
    return activeNetwork != null
            && activeNetwork.isConnectedOrConnecting();
}