Silverlight Bing Maps with web services

using Microsoft.Maps.MapControl;
private void Dynamic_Click(object sender, RoutedEventArgs e)
        {
            double latitude = 0;
            double longitude = 0;
            double.TryParse(tbLatitude.Text, out latitude);  
            double.TryParse(tbLongitude.Text, out longitude);  
            this.map.SetView(new Location(latitude, longitude), 5);  
        }
when I input the latitude and longitude through two textboxes,and click the button, the view of map always location on a same and wrong position, why? help me,please ,thank u.
 

Usually when this is happening, the try parse is failing and your long and lat will be 0 or it could be a different number if the parse works but the default culture doesn't recognise the number as a double. This is normally because of regional settings in how doubles are handled in your operating system

If you use the System.Globalization namespace

and the following code

double.TryParse(tbLatitude.Text,NumberStyles.Float,CultureInfo.InvariantCulture, out latitude);

This should solve your issue.

Also check what value is being outputted and if you are getting a true or false in the tryParse