Catching errors or exceptions - asp.net

Question

I built a mashup of google maps and weather.com and everytime one of these server is not responding my application hangs up too.What do you think I can do to prevent or minimize hanging up of my web apps?Hanging up like you can't navigate away from that page....
I got this code on my app code to access the weather service;
Public Class WeatherIn
Private _path As String
Private _cachedFile As String
Public Sub New(ByVal path As String)
_path = path
_cachedFile = String.Format("{0}\WeatherInCache.xml", _path)
End Sub
Public Function GetWeather(ByVal arg As String) As String
Return _getWebWeather(arg)
End Function
Private Function _getCachedWeather() As String
Dim str As String = String.Empty
Using reader As New StreamReader(_cachedFile)
str = reader.ReadToEnd()
End Using
Return str
End Function
Private Function _getWebWeather(ByVal arg As String) As String
Dim baseUrl As String = "http://xoap.weather.com/weather/local/{0}?cc=*&dayf=5&link=xoap&prod=xoap&par={1}&key={2}"
Dim jane As String = arg
Dim james As String = "api key"
Dim john As String = "another api key"
Dim url As String = String.Format(baseUrl, jane, james, john)
Using client As New WebClient()
Try
Dim xml As New XmlTextReader(client.OpenRead(url))
Dim xslt As New XslCompiledTransform()
xslt.Load(_path + "/Pathto.xslt")
Using writer As New StreamWriter(_cachedFile)
xslt.Transform(xml, Nothing, writer)
End Using
Return _getCachedWeather()
Catch exception As WebException
Dim xmlStr As String = "<errorDoc>"
xmlStr += "<alert>An Error Occurred!</alert>"
xmlStr += [String].Format("<message>{0}</message>", exception.Message)
xmlStr += "</errorDoc>"
Dim doc As New XmlDocument()
doc.LoadXml(xmlStr)
Dim reader As New XmlNodeReader(doc)
Dim xslt As New XslCompiledTransform()
xslt.Load(_path + "/Pathto.xslt")
Dim resultDocument As New XmlDocument()
Using writer As XmlWriter = resultDocument.CreateNavigator().AppendChild()
xslt.Transform(reader, DirectCast(Nothing, XsltArgumentList), writer)
End Using
Return resultDocument.OuterXml
End Try
End Using
End Function
Then I used the class above on my page where I display the weather like this:
'specific zip code or could be retrieved from querystring for dynamic retrieval
var jay="94576"
Dim weather As New WeatherIn(Server.MapPath(String.Empty))
Dim weatherData As String = weather.GetWeather(jay)
Response.ContentType = "text/xml"
Response.CacheControl = "no-cache"
Response.Write(weatherData)
which I retrieve the data and write on the page through javascript.Most of the time its the weather.com that goes down.I got no problem with google map its reliable....anybody got a solution why my page hangs up too if the remote server is not responding?The mashup is running smoothly if the remote server is responding...

Answer 1

When depending on external web services it is best to load asynchronously so that if one of them is slow you can show some kind of loading spinner to the page viewer. If it fails your page could simply report that reading from the web server failed and to try again later.
In this case I would load up the page with the Google map in place and then make an AJAX request for the Weather data.